# Airplane Riddle



## bearintex (Feb 7, 2006)

Shamelessly stolen from another message board I frequent, this riddle has gotten over 250 replies in just acouple of days.

The riddle:

A plane is standing on a movable runway(something like a conveyor) As the plane moves, the conveyor moves but in the opposite direction. The conveyor has a system that tracks the speed of the plane and matches it exactly in the opposite direction.

The question is, will the plane take off or not and why, or why not.


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## boom! (Jul 10, 2004)

No. It must generate lift by moving the wing through the air.


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## speckle-catcher (May 20, 2004)

no

from what i remember of the properties of lift - there must be airflow over and under the wing in order to generate lift. If the plane is essentially motionless, there is no air flow and it will not fly...it will continue to run on the conveyor as fast as the engines can take it.


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## MrG (Apr 10, 2005)

Nope. Assuming the plane is staying in the same spot. No airspeed. No lift. 

Just guessin.


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## speckledred (Jun 1, 2004)

Nope. No wind speed to create lift, won't fly.


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## Hullahopper (May 24, 2004)

If the net ground speed of the plane is zero I'm thinking that plane isn't going anywhere.


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## EGT Limited (Jul 30, 2004)

Nope, no airflow to create lift.


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## mastercylinder60 (Dec 18, 2005)

considering this is not a trick question, no, the plane will not take off. getting an airplane aloft depends entirely upon airspeed and the aerodynamics of the wing surface, and getting enough airspeed so that a greater air pressure is created under the wing than is over the wing.

so, if the conveyor was moving at a rate to counteract the forward motion of the plane, the windspeed would not be enough to to create enough positive pressure under the wing to get the plane aloft.

getting an airplane aloft is all about physics.


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## Mrs Backlasher (Dec 19, 2004)

I don't know anything about that stuff, but I'm guessing "YES" the plane will take off.

If the plane is traveling at a certain speed in one direction, and the conveyor is traveling at the same speed in the opposite direction, I would think that the air passing across the wings would be twice the speed of the plane.

Just a guess.


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## Mrs Backlasher (Dec 19, 2004)

Is this one of those funny answers, like... No, it won't fly, it's on a merry-go-round?


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## bill (May 21, 2004)

No. No lift, no take off on a fixed wing. Only a harrier that provides it's own lift (something like 20,000+ pounds of thrust) would it achieve takeoff.


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## fishnlab (Jul 10, 2004)

of course it will take off. Assuming the plane has jet turbine engines, or some sort of propeller. 

The idea that it would not lift off because it is not "moving" would be true if the planes propulsion was created by spinning the wheels quickly, like a car.

The plane I'm picturing (737, 777, cessna, etc.) creates thrust with its engines, and moves air. It will lift, and will fly.


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## K_REDDY (May 13, 2006)

I agree with fishnlab. The planes engines will move the plane no matter what direction the con. belt is moving. the plane will take off, the wheels will actualy be turning twice as fast.


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## Freshwaterman (May 21, 2004)

.


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## bill (May 21, 2004)

Here is a test. (If the runway was longer, it would still apply)


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## fishsmart (Dec 5, 2004)

The airplane is not fixed or secured to the "conveyor belt". The airplane moves forward as the wheels rotate and the airplane accelerates to gain lift and takeoff.

Charles


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## troy merrill (May 21, 2004)

I'll go with YES. First reason, the answer to these is always the opposite of what you expect. Second reason, I do not think planes generally depend on the wheels to take off.....isn't that why the have propellors or turbines (for jets)?


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## boom! (Jul 10, 2004)

In order to create lift, the same amount of air must travel a greater distance above the leading edge of wing than below the wing. That is why wings are the shape that they are. If the plane, prop, jet, or rubber band powered is not moving the wing through the air due to the moving conveyor, no lift will be created.


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## fishnlab (Jul 10, 2004)

fishnlab said:


> of course it will take off. Assuming the plane has jet turbine engines, or some sort of propeller.
> 
> The idea that it would not lift off because it is not "moving" would be true if the planes propulsion was created by spinning the wheels quickly, like a car.
> 
> The plane I'm picturing (737, 777, cessna, etc.) creates thrust with its engines, and moves air. It will lift, and will fly.


LOL!!
no flight for this plane on this runway.

let's say a 737 needs to travel at 150mph ground speed to take off...(I don't know what the real number is, would depend on winds, elevation, etc.)...if your conveyor belt plane did, indeed, lift off, would it not have to instantly reach 150 MPH in order to stay in the air? That would be a sight to see.


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## Hullahopper (May 24, 2004)

How do you find these things? LOL!



bill said:


> Here is a test. (If the runway was longer, it would still apply)


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## Pocboy (Aug 12, 2004)

Those wheels would be spinning at an incredible. What if there were 1000 geese each weighing 10 pounds in the plane and at 10,000 feet they suddenly began flying around the cabin in a circular patter. Would the plane jump up because it is 10,000 pounds lighter.


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## boom! (Jul 10, 2004)

I would bet that conveyors are cheaper than catapults (sp).


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## troy merrill (May 21, 2004)

How much "wind" is the conveyor belt going to kick up?


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## dennis_99 (Feb 27, 2006)

I think the answer is NO because a plane gains lift by high air pressure under the wing, and forward motion by high air pressure behind the engine.
IF this were possible, I think this technology would have already been used on aircraft carriers.


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## FishDByrd (Mar 23, 2006)

boomgoon said:


> I would bet that conveyors are cheaper than catapults (sp).


Probably not and there are a lot more moving parts to maintain to keep a conveyor rolling. A lot of $$ spent on maintenance of conveyors moving pet coke and sulphur around the ship channel.


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## Wes (Apr 1, 2005)

It would take off. As, stated earlier the wheels are not needed to move forward. 

The thrust from the props or jet engine would still propell the aircraft forward. The wheels would just be turing at twice the revolutions of the normally would but the aircraft would still take off.


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## boom! (Jul 10, 2004)

Wes said:


> It would take off. As, stated earlier the wheels are not needed to move forward.
> 
> The thrust from the props or jet engine would still propell the aircraft forward. The wheels would just be turing at twice the revolutions of the normally would but the aircraft would still take off.


The way it is stated, the conveyor would overcome forward motion.


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## Boaz (May 17, 2006)

bearintex said:


> Shamelessly stolen from another message board I frequent, this riddle has gotten over 250 replies in just acouple of days.
> 
> The riddle:
> 
> ...


Sure the plane will take off. How fast the wheels on the plane are turning has absolutely nothing to do with its ability to fly. Duh.


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## BCTX4x4 (Mar 3, 2005)

I know this isn't a myth, but this type of question would be great to send to the mythbusters and see if they could some how create this scenario and see if it would or wouldn't work even though the only way they could do it is to create a scaled down version of it.


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## dennis_99 (Feb 27, 2006)

Boaz said:


> Sure the plane will take off. How fast the wheels on the plane are turning has absolutely nothing to do with its ability to fly. Duh.


Exactly right, the wheels (ground speed) don't matter, however the lift by high air pressure under the wing, and forward motion by high air pressure behind the engine will be lacking if the only thing moving is the conveyor belt.


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## bill (May 21, 2004)

For a fixed wing craft, no forward motion, no lift
the engines do not create the lift on the wings...the airflow over/under the wings gives it lift


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## Cat O' Lies (May 21, 2004)

Ok, your sitting in your living room! You have a conveyor belt right in front of your TV and on that conveyor belt sits your motorcycle. You get the motorcycle up to speed, say 60mph! At the same time, the converyor belt is moving backwards at 60mph. (The conveyor belt speed mirrors your motorcycles speed) So, you drive your motorcycle for 3 hrs and then slow down to a stop. At the same time the conveyor belt slows down to 0 mph. When you get off, where will you be????

That plane uses the engines to propel forward fast enough to create lift. If you anchor the plane to a stationary object the engines alone will not create enough lift for it to fly.


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## MrG (Apr 10, 2005)

boomgoon said:


> The way it is stated, the conveyor would overcome forward motion.


That's as simple as it gets. No ground speed = no air speed = no moving air over the wings = no lift = no fly.

Now if the wind were blowing 150mph, that would be a different story.LOL


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## speckle-catcher (May 20, 2004)

Cleveland?


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## boom! (Jul 10, 2004)

BCTX4x4 said:


> I know this isn't a myth, but this type of question would be great to send to the mythbusters and see if they could some how create this scenario and see if it would or wouldn't work even though the only way they could do it is to create a scaled down version of it.


Good point. I already know it won't fly, but I'd love to see what they do to it when it won't! LOL.


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## boom! (Jul 10, 2004)

MrG said:


> That's as simple as it gets. No ground speed = no air speed = no moving air over the wings = no lift = no fly.
> 
> Now if the wind were blowing 150mph, that would be a different story.LOL


160mph at flaps 20, then yes! LOL


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## Too Tall (May 21, 2004)

bearintex said:


> Shamelessly stolen from another message board I frequent, this riddle has gotten over 250 replies in just acouple of days.
> 
> The riddle:
> 
> ...


Take a long runway and alot of power but yeah it will fly. Assuming it is as written the plane is not stationary. Engine thrust will still propel the aircraft forward and generate lift. Doesn't matter how fast the wheels are turning. An aircraft doesn't rely on the wheels for motion. Just steering. 
A car on the other hand relies on power to the wheels relayed to the ground to achieve forward motion. Same scenario the car wouldn't move.


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## bill (May 21, 2004)

Size of the runway does not matter..the plane never moves. Unless there is a way to overcome Newton's Third Law, the plan will not fly.


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## boom! (Jul 10, 2004)

If I am running 10 mph on a treadmill going 10 mph in the oposite direction, how long would the treadmill have to be for me to get to the fridge?


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## speckle-catcher (May 20, 2004)

Google search "plane conveyor" and read some of the stuff that comes up.

Here's a couple of gems I found:



> What would really happen is the wheels would spin so fast and generate so much heat before the plane reached the appropriate takeoff speed that they would explode in a fiery rubbery ball of rage, causing the plane to crash down onto the conveyor belt, at which point it would explode in a fiery metal ball of rage, and would eventually be thrown off the conveyor belt, which was coincedentally set up in front of a fazed gathering, and everyone that participated in this thread except for me would be blown to smithereens in a fiery ball of irony.





> You're wrong. Here are the facts, yet again:
> 
> 1. The color of the pilot's socks, what he/she ate for breakfast, the weight of 10 penguins, and the wheel speed of the airplane all have the same importance when considering this riddle, which is to say absolutely none.
> 
> ...


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## MrG (Apr 10, 2005)

boomgoon said:


> If I am running 10 mph on a treadmill going 10 mph in the oposite direction, how long would the treadmill have to be for me to get to the fridge?


That depends on how much beer is in it.


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## boom! (Jul 10, 2004)

Waaaaaait..... What if I hit the reverse thrusters?


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## triple f (Aug 23, 2005)

Treadmill Riddle #2


You buy a $400 treadmill at Sears. Take it home, rearrange the bedroom and place it strategically in front of the TV, plug it in and raise the Incline to 15 degrees.

Can you still hang as many clothes off of said treadmill as you could with the incline at 0 degrees?


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## bill (May 21, 2004)

Has anyones brain melted? LOL

The answer is no LOL


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## Gottagofishin (Dec 17, 2005)

I only read the first page, so someone may have already got it, but since a plane's motion is generated by jets or props, the conveyor won't prevent the plane from moving forward and generating lift. The only impact is that the wheels will spin twice as fast.

I promise I didn't cheat. Do I win anything?

Great riddle though.


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## Texas T (May 21, 2004)

If it's power to weight ratio is like a jet fighter in afterburner it could, or if it is called an Osprey it could or if the treadmill had a very strong wind blowing across it it could. A even better question to ponder is if a 747 was full of pigeons sitting inside of it would it be lighter if they all started flying around inside of it.


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## fishnlab (Jul 10, 2004)

Gottagofishin said:


> I only read the first page, so someone may have already got it, but since a plane's motion is generated by jets or props, the conveyor won't prevent the plane from moving forward and generating lift. The only impact is that the wheels will spin twice as fast.
> 
> I promise I didn't cheat. Do I win anything?
> 
> Great riddle though.


Sorry...you have to suffer through the entire thread to be eligible for a prize.


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## Gottagofishin (Dec 17, 2005)

fishnlab said:


> Sorry...you have to suffer through the entire thread to be eligible for a prize.


I knew there was a catch. LOL!


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## bill (May 21, 2004)

During take off, thrust must be greater than drag and lift must be greater than weight so that the airplane can become airborne. It's a tug of war. 4 forces at work here. Drag, thrust, lift and gravity. The lift is caused by air moving over the wings.


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## speckle-catcher (May 20, 2004)

and if the plane never moves forward, there can be no air to creat lift. 

so it still don't fly.


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## bill (May 21, 2004)

speckle-catcher said:


> and if the plane never moves forward, there can be no air to creat lift.
> 
> so it still don't fly.


That has been my point from my first post on this subject. You can not forget newton's third law.


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## PiratesRun (Jun 23, 2004)

*Newton*

I love Newton's Laws. Physic's rules.

F=MA


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## Guest (Dec 7, 2006)

I'm not sure it is possible to set up the situation so that the plane remains in one place. If you can, then the plane will not fly, but since its forward motion is not dependent upon wheel speed will the plane stay still? . . . on the other hand, what if you think of the conveyor as a reverse aircraft carrier catapult? ???



:rybka:


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## Gottagofishin (Dec 17, 2005)

speckle-catcher said:


> and if the plane never moves forward, there can be no air to creat lift.
> 
> so it still don't fly.


That is true.

But the point of the riddle is that an airplane's forward motion comes from props or jets, not it's wheels. Therefore, as long as the wheels are free spinning, the jets will move the plane forward no matter how fast the conveyor is moving, and the plane will take off.


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## bill (May 21, 2004)

the plane has no forward motion


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## MrG (Apr 10, 2005)

speckle-catcher said:


> and if the plane never moves forward, there can be no air to creat lift.
> 
> so it still don't fly.


I don't think they get that the plane is making no forward progress.


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## fisherking78 (Dec 18, 2005)

Ask this you gasoline alley dwellers. 

Does it take more, less, or equal energy to inflate a car tire, if it is mounted on the car or on the ground and why? Good question for a high school physics class.


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## Gottagofishin (Dec 17, 2005)

MrG said:


> I don't think they get that the plane is making no forward progress.





> A plane is standing on a movable runway(something like a conveyor) *As the plane moves*, the conveyor moves but in the opposite direction. The conveyor has a system that tracks the speed of the plane and matches it exactly in the opposite direction.


 Why do you assume the plane is making no forward motion? Think about it.


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## speckle-catcher (May 20, 2004)

Gottagofishin said:


> That is true.
> 
> But the point of the riddle is that an airplane's forward motion comes from props or jets, not it's wheels. Therefore, as long as the wheels are free spinning, the jets will move the plane forward no matter how fast the conveyor is moving, and the plane will take off.


the way I see it -

it does not matter if the plane is propelled forward by jet turbines or propellers - the plane starts out at a ground speed of 0. as the engines move the plane "forward", the "ground" (conveyor) travels in the oppsite direction at the same velocity. Even as the plane speeds up, the wheels are still touching and travelling on the ground that is moving backwards as fast as the plane move forwards. So the plane will have no forward motion.

make sense?

I should draw a free body diagram


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## Outcast (May 20, 2004)

I didn't know planes could stand but since it is "standing" on the conveyor i would assume it's pointing upward. If the conveyor moves in the opposite direction (down) then I assume the plane would be lifting off. Boy....................bet I'm way off base!


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## huntinguy (Aug 22, 2005)

do they still serve nuts on this plane even if it isn't moving forward?...........can I get a window seat?


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## bill (May 21, 2004)

speckle-catcher said:


> the way I see it -
> 
> it does not matter if the plane is propelled forward by jet turbines or propellers - the plane starts out at a ground speed of 0. as the engines move the plane "forward", the "ground" (conveyor) travels in the oppsite direction at the same velocity. Even as the plane speeds up, the wheels are still touching and travelling on the ground that is moving backwards as fast as the plane move forwards. So the plane will have no forward motion.
> 
> ...


Here ya go


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## Gottagofishin (Dec 17, 2005)

speckle-catcher said:


> the way I see it -
> 
> it does not matter if the plane is propelled forward by jet turbines or propellers - the plane starts out at a ground speed of 0. as the engines move the plane "forward", the "ground" (conveyor) travels in the oppsite direction at the same velocity. Even as the plane speeds up, the wheels are still touching and travelling on the ground that is moving backwards as fast as the plane move forwards. So the plane will have no forward motion.
> 
> ...


You're thinking cars. A car's wheels propel it forward using the ground to push off of. If the ground is a conveyor, moving at the same speed as the wheel's rotation, then the car will never move forward.

An airplane however is essentially thrusting itself forward by accelerating air from the jets or prop at a higher speed than the surrounding air. An airplane's wheels have nothing to do with it's forward thrust, and the conveyor has no affect on the movement of the air. As such, the conveyor and the airplane's wheels have nothing to do with the plane's ability to move forward. If the jets or prop can move air at a more rapid rate than the surrounding air, then the airplane can move forward.

The only impact the moving conveyor has is that the wheels will rotate twice as fast as they would normally. However, assuming they are free spinning, this has no impact on the ability of the airplane to move forward.


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## bill (May 21, 2004)

the plane can not move forward
action(wheels)=reaction(conveyor belt)

if you have no forward movement, there is no air moving over the wings and then you have no lift
without lift the plane can not fly

gravity will hold the plane on the ground
in this case we have done nothing to remove gravity


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## huntinguy (Aug 22, 2005)

um..........i'm gonna play ignorant here (cuz i do it so well) and ask a question..............what makes the wheels spin for the conveyor to react to?


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## speckle-catcher (May 20, 2004)

the original question does not specify


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## Gottagofishin (Dec 17, 2005)

Okay. Let me put it this way. It's a riddle. The correct answer is not the obvious one.


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## Tall Steve (Jun 22, 2004)

Plane will take off.

The the conveyer will never catch up to the speed of the wheels. Since the wheels are free spinning and the thrust comes from the jet/props the wheels will just continuely move faster.

The fact that the conveyer is moving backwards does not keep the plane from moving forward.


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## Tall Steve (Jun 22, 2004)

The conveyor matches the speed of the wheels not of the plane. The conveyor would end up going mutch faster backwards than the plane is traveling forwards.


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## bill (May 21, 2004)

Anyone ever have a race car? Did you take it to a shop and use a dynamometer? I would guess this to be the same, no matter how much force, torque is spent, the car never takes off (hope it don't anyways).


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## Badhabit (May 20, 2004)

bill said:


> the plane can not move forward
> action(wheels)=reaction(conveyor belt)
> 
> if you have no forward movement, there is no air moving over the wings and then you have no lift
> ...


Bill my Bro, you just ain't gettin the theory....... The wheels nor conveyor has nothing to do with the propulsion on the airplane. the airplane is propelled by a propeller, which pulls and pushes air, the conveyor has nothing to do with the air movement, even tho the conveyor is moving, it will have no effect on the way the prop pulls the AIRplane thru the air, the wheels will be spinning their arse off but that don't matter, the force of the prop will pull the plane thru the AIR no matter how fast the conveyor is spinning, because the free spinning wheels of the airplane and the conveyor have nothing to do with the AIR propulsion created by the propeller.... I admit it would take a rather long conveyor for the plane to build up AIRspeed, and the planes wheels would be spinning double fast, but the answer is the plane WOULD TAKE OFF in the same amount of AIR space as normal, in other words, the conveyor is NOT causing ANY drag as the wheels on a plane FREESPIN......The wheels ain't pushing the plane, the prop is. now if the air was blowing WITH the direction of takeoff above the stall speed of the plane, then it won't lift off.....

My ground class instructor asked the same question on our last session.... That was one week before I got my pilots license...........


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## Life Aquatic (Oct 24, 2006)

Whats the air speed volocity of a European swallow? Depends on whether it is carrying a coconut.

I bet a Harrier wouldn't have a problem taking off or a regular plane for that matter.


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## Badhabit (May 20, 2004)

bill said:


> Anyone ever have a race car? Did you take it to a shop and use a dynamometer? I would guess this to be the same, no matter how much force, torque is spent, the car never takes off (hope it don't anyways).


Bro, the wheels don't propell an AIRplane........


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## Gottagofishin (Dec 17, 2005)

bill said:


> Anyone ever have a race car? Did you take it to a shop and use a dynamometer? I would guess this to be the same, no matter how much force, torque is spent, the car never takes off (hope it don't anyways).


Again your thinking cars not planes. A car's thrust comes from the wheels, plane's thrust does not. That's the key to the riddle.

Put a skate board on a moving conveyor belt and hold it there. Is it hard to hold it still? It shouldn't be. Now push the skateboard against the direction of the conveyor. Is it hard to push? No.

Why? because the wheels are free spinning and have nothing to do with propelling the skateboard. You pushing is what moves the skateboard. As long as the wheels spin, it doesn't matter how fast the conveyor is moving. You can still easily push the skateboard against the direction of the conveyor.

In the riddle the plane's wheels are like the skateboard's. They don't have anything to do with propelling the plane. They just roll. The jets or prop are like your hand that pushed the skateboard. Their ability to push isn't affected by the conveyor.

Make sense?


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## speckle-catcher (May 20, 2004)

well if it is going to take off - is there going to be an in-flight movie?


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## scwine (Sep 7, 2006)

*Googled it and they say Yes.........*

http://www.oshawapilot.ca/?p=416

obviously this question has been around quite a bit. I was surprised to see so many search results. Here is one of them.


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## Badhabit (May 20, 2004)

speckle-catcher said:


> well if it is going to take off - is there going to be an in-flight movie?


There was a video the other day of airplanes skimming the water, do you think those wheels were spinning when they hit the water ????? Why didn't the plane stop ???? Because the plane don't rely on the wheels for forward motion, it relys on AIR....... Dats why it's called an AIR plane.... The ground surface makes no difference as long as it's smooth.......


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## Mrs Backlasher (Dec 19, 2004)

So..... what's the answer to the riddle? When will we know?


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## Too Tall (May 21, 2004)

I agree with BH and Gottago. And did so back on page 2. That bird is going up. Better grease the wheel bearings because those suckers are going to be screaming.
The dyno is completley opposite from this. A car has to deliver power to the ground thru the tires for motion to occur. Thats why on a dyno it wouldn't move. Put a plane on a dyno and push the throttle. The plane would hop off. It does not rely on power to the ground for forward motion


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## timbo (May 22, 2004)

If the runway's long enough, it's getting off the ground.


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## Mr. Breeze (Jan 6, 2005)

So, we don't need runways anymore. Airports could be much smaller.


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## jimk (May 28, 2004)

From way back when...I always thought that "lift" came from air flowing past the wing and the camber...the curved top was to create a longer surface than the bottom so that the air on top went "faster" than the air on bottom which created lower pressure on top than on the bottom to create lift or moving toward lower pressure. Does an engine, at WOT sitting still have the capability of creating the same uniform airflow over the wing surface as if it were rolling along at rotation speed? I may be wrong, but if you could hold the brakes....rev up the prop/turbine or whatever to the same rpm as take off speed....you should be able to release the brake and pull the nose up....right? Since the wheels don't matter, what's the difference between this and the conveyor? The thing that sticks in my mind is that the airflow between sitting still and moving at rotation speed is the difference in airflow past the wings. Isn't that why you have a takeoff roll? Then there's the problem of thrust of really powerful engines. I hate these problems....wish someone had a long conveyor belt.


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## bearintex (Feb 7, 2006)

bill said:


> Anyone ever have a race car? Did you take it to a shop and use a dynamometer? I would guess this to be the same, no matter how much force, torque is spent, the car never takes off (hope it don't anyways).


Fallacy there, mi amigo. While on the dyno, the car is STRAPPED down. It can't go anywhere.

Of course the plane will fly. It's wheels will simply be turning at twice the equivalent speed of the plane at the time of takeoff. Since the thrust is applied to the air, and not to the ground through the wheels, the plane moves completely independent of the conveyor. Think of sitting on a skateboard on a treadmill. Even with the treadmill at full speed, it's a pretty simple effort to pull yourself forward by the handrails. Same thing, you're applying the forward force to something other than the rolling portion of the conveyor.


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## boom! (Jul 10, 2004)

Where do you get lift?


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## Too Tall (May 21, 2004)

From the wind over the wings when the aircraft reaches takeoff speed. The wheels might be smoking but the bird is going to fly.


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## jimk (May 28, 2004)

When that 150 or 172 lifts off into a 10 knot wind....just my opinion...but I think you'll see the rpm's drop (drastically) and the nose dip...depending on the power of the thrust, it may or may not continue flying. Maybe if we point a whole bunch of cessna's to the east at full throttle with brakes on, we might even change the rotation of the earth.LOL


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## Sight Cast (May 24, 2004)

BH hit the nail on the head. Conveyor belt or not forward thrust is causing lift on the wings.


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## bill (May 21, 2004)

I'm sorry, I should not have used the dyno...it made things worse. I was trying to say that no matter the speed of the tires, the plane will not move, if the plane don't move you get no forward motion.

The lift is produced as air moves over the wings. If you double the thrust, or increse as much as you want, the belt keeps pace and you do not move forward. The size of the runway does not matter...you never move forward.

LOL
I'll stand with Newton's 3rd Law.


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## Too Tall (May 21, 2004)

http://txfx.net/2005/12/08/airplane-on-a-conveyor-belt/


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## bill (May 21, 2004)

I sent it in to mythbusters. If everyone else did, and then they looked up all the threads a nd post on the www, they might do a show. It would of course be a scaled down version. Or someone loan me a few billion and lets get to work. LOL


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## speckle-catcher (May 20, 2004)

ya'll are winning me over. I'm seeing the (f)light 

as long as we're on a plane, can we go some place warm...like Cozumel?


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## Freshwaterman (May 21, 2004)

The logical scientific answer is no because of the above mentioned reasons. However thinking outside the box I have other ideas. If its a VTOL(vertical take off and landing) aircraft like the harrier it doeasn't matter of the airspeed etc it doesn't even need a runway. For that matter I do believe even a regular plane would take off given suuficient fuel and a capable pilot...I mean this conveyor can't go on forever and whats the use of wasting a perfectly good airplane sitting on one for all eternity. Also, is there wind? If there were suffcient wind and the plane were facing the right direction it would be capable of leaving the ground would it not, if not a gale force wind simply throwing it off the runway. Last but not least, as mentioned in most contracts concerning liabilty.........an act of god could move that plane. :cheers:

Sincerely,

Chance


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## stargazer (May 24, 2004)

BH and Gottogo has it.


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## triple f (Aug 23, 2005)

Did anyone else catch onto the fact that Badhabit is a licensed pilot?!?!? 

I reckon he would be classified as a BUS(C)H pilot


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## scudrunner (May 21, 2004)

So the fact that the "runway" is rolling backwards at the same rate the airplane is rolling forwards providing zero airspeed has nothing to do with it?
The car vs airplane analogy has some merit. How about if we put a thrust jet on a car so the wheels are no longer providing the proplution? Would the answer be different?
The fact is for an airplane to fly, it must have forward airspeed, regardless of how it is achieved (see wind tunnel). A Cessna 150 can take of with no ground speed in a 55 mph wind (personal experience).


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## triple f (Aug 23, 2005)

bearintex said:


> A plane is standing on a movable runway(something like a conveyor) *As the plane moves*, the conveyor moves but in the opposite direction. The conveyor has a system that tracks the speed of the plane and matches it exactly in the opposite direction.
> 
> The question is, will the plane take off or not and why, or why not.


OK, the way I see to splain this........the plane is moving 100 mph, the conveyor is moving 100 mph in the opposite direction, resulting in a wheel speed of 200 mph.....but _the plane is still moving 100 mph_, so if flight can be achieved at 100 mph then we are airborne!

Stewardess, I'll have a Crown and Coke please.....and KEEP EM COMIN!


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## bill (May 21, 2004)

my wife (the real brains of the family) just laughed at us...she said we all need to spend the night in a Holiday Inn


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## txjoker (Jun 21, 2005)

This is a response from my girlfriend who has her pilot's license:

The plane will not take off. What makes the plane take off has to do with air flow over the wings, that's why planes have to be tied down in windy weather and why in VERY windy weather, little airplanes can fly backwards. Planes take off INTO the wind--so whichever way the wind comes from is the direction the plane takes off. That's why there are different runways going in different directions. If there is no airflow, the plane won't fly, it will actually drop out of the sky in a spectacular tailspin.

P.S. She also adds:

There are four principles in flight: Thrust (what propellers create), lift (created by airflow), drag (created by the body of the airplane) and weight (the mass of the airplane). The propellers won't create enough wind to make lift. (By the way, cold air works better than hot air, and some jets have their engines in the tail, so no flow goes over the wings.)


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## Too Tall (May 21, 2004)

You have to quit looking at it like it was a car. The plane will fly only the wheel speed will be twice the ground speed.


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## boom! (Jul 10, 2004)

Ding ding ding... txjoker is a winner. Except for the spelling of pilot, his post is dead on the money! LOL

I can't wait for myth busters to prove us wrong!

PS.... 100 post woooohoooo!


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## Bimini Twisted (Apr 17, 2005)

I suggest ya'll drop a little boy or fat man over this fictional plane and be done with it.

heh,
Rick


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## bill (May 21, 2004)

Too Tall said:


> You have to quit looking at it like it was a car. *The plane will fly only the wheel speed will be twice the ground speed.*


Thats the problem. It will never go twice the ground speed.

LOL This is close to making me want a drink...LOL


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## txjoker (Jun 21, 2005)

hehe Sorry about that! My spelling gets worse the more I type. Went back and fixed it just for you, boom. 



boomgoon said:


> Ding ding ding... txjoker is a winner. Except for the spelling of pilot, his post is dead on the money! LOL
> 
> I can't wait for myth busters to prove us wrong!
> 
> PS.... 100 post woooohoooo!


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## bearintex (Feb 7, 2006)

You're always going to have a vocal few who cannot seem to fathom that the plane is moving. Yes, the conveyor is moving at an equal speed in the opposite direction. But all that does is double the indicated velocity of the wheel's rotation. The plane will take off as normal, maybe a few extra feet due to the increased friction drag from the higher wheel speed.


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## GoingCoastal (May 24, 2004)

triple f said:


> Did anyone else catch onto the fact that Badhabit is a licensed pilot?!?!?
> 
> I reckon he would be classified as a BUS(C)H pilot


I did and was going to mention it when I had a minute.

I live near airport in baytown and that explains the mysterious falling beer cans.

Dave

greeny for bus(c)h pilot.


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## boom! (Jul 10, 2004)

Bear, The plane is already moving 17,000 mph at the gate, why does it not take off there?


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## txjoker (Jun 21, 2005)

Here is a response from one of our science teachers:

The plane will not take off. To achieve lift, it must have air moving over it's wings. If the air speed is enough (I'm guessing around 100mph for a big heavy jet), then the upward lift will be enough to carry the plane into the sky. In your scenario there is no air moving over it's wings, so no lift is achieved.

Alternate scenario, using this concept: The plane is sitting still on the ground. A hurricane comes along, with winds over 100mph. Assuming that the winds are hitting the plane head-on, the plane will actually try to lift off of the ground (I don't mean blown around, I mean fly), even though it's engines are off. That's how they test airfoil shapes in wind tunnels. Keep the airfoil still, and blow air over it with a little smoke so that you can see what's going on...


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## boom! (Jul 10, 2004)

http://www.zianet.com/tedmorris/dg/bombers4.html

These guys are pilots also.


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## seawings (Aug 28, 2004)

I am not an aeronautical engineer, however my answer would be no!!

Why...because an airplane needs *"air speed". *Airspeed is the speed of the air over the wing.

Another speed is *"ground speed"* ...is the speed to the airplane over the ground.

As an example...if the airplane was sitting still and your calculated take-off speed required was 145 knot and you had a steady state wind of 145 knots the airplane would be at lift off speed right then and there!! and then it could take off with *no* ground speed.


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## Too Tall (May 21, 2004)

bill said:


> ...she said we all need to spend the night in a Holiday Inn


Can we get a group discount.


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## CP (Aug 6, 2005)

*Confessions from a "POSITIVE No-FLY"*

It will fly.

I was convinced by the following analogy.

Take a can of soup(the plane) and put it on the conveyor belt.

Use your hand (the jet thruster) to hold the can in place on the belt, with the belt moving. At this point the work of your hand is opposed by the belt.

The question becomes "can you push the can forward if the belt speeds up?" Yes.

The jet thruster (otherwise known as your hand) will easily push the can to the end of the conveyor belt even if the belt speeds up.

All the way up to the point where the belt speed approachs the speed of light and the can is just a millisecond away from exploding chunky meaty campbells all over everthing you can still push the can off the conveyor belt.


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## bill (May 21, 2004)

CP said:


> It will fly.
> 
> I was convinced by the following analogy.
> 
> ...


The can/belt don't work. The belt stays at a "set"
speed and that allows the can to move forward. If the belt was to increase speed to match the can, it would not/could not move forward.


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## txjoker (Jun 21, 2005)

There is no airspeed in your theory, though.



CP said:


> It will fly.
> 
> I was convinced by the following analogy.
> 
> ...


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## speckle-catcher (May 20, 2004)

I've changed my mind. 

The plane will fly.

think of it this way: imagine the plane sitting on the conveyor. The plane's engines are off and the conveyor is stopped.

start the conveyor, but leave the plane engines off. In a "perfect environment" we would assume no friction at the wheel bearings on the wheel, so the conveyor will be moving backwards but the plane will stand still on the runway, because the wheels are spinning in place.

now start the plane's engines. it will move forward and will fly once it gets enough speed up.


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## jdkliesing (Nov 9, 2006)

*The airplane takes off*

As long as the plane's wheels arefree to roll, the conveyor belt can move either forwards or backwards,at any speed, but the engines will exert thrust and the aircraft will aquire airspeed, and will liftoff regardless the belt. The wheels of the aircraft will just spin twice as fast. This is not a car it gets its "thrust"from the air not the ground.


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## bill (May 21, 2004)

speckle-catcher said:


> I've changed my mind.
> 
> The plane will fly.
> 
> ...


Why? At what point would the wheels move faster that the belt?


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## jdkliesing (Nov 9, 2006)

bill said:


> Why? At what point would the wheels move faster that the belt?


the second the plane moves forward, if the plane is going 10mph the wheels will be spining at 20 mph 10mph forward + 10mph backwards = wheel speed 20 mph. The belt is fighting to keep an object in place but the object is not useing the ground to propel itself its using air the wheels will only spin.


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## Too Tall (May 21, 2004)

speckle-catcher said:


> I've changed my mind.
> 
> The plane will fly.
> 
> ...


Welcome to the dark side.


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## Badhabit (May 20, 2004)

Ding ding ding......... Bout time Bro...... LMAO



speckle-catcher said:


> I've changed my mind.
> 
> The plane will fly.
> 
> ...


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## GoingCoastal (May 24, 2004)

What if there were " SNAKES on the MF'n Plane " 

Anybody see that movie ?

Dave


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## bill (May 21, 2004)

GoingCoastal said:


> What if there were " SNAKES on the MF'n Plane "
> 
> Anybody see that movie ?
> 
> Dave


LOL I wanted to see that movie....reviews said it kinda bombed...but I don't care. I just wanted to go because my wife hates snakes. LOL
Now we could add the snake factor in.....if I was on the plane (full of snakes) I would get out and push.

On second thought, there would be no reason to push, not like I was going to get back on or anything...LOL


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## greg77 (May 22, 2006)

The only way the plane is getting off the ground is if it's a Harrier or an Osprey.


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## spawningbedassassin (Jul 11, 2006)

Here is an interesting website.

http://txfx.net/2005/12/08/airplane-on-a-conveyor-belt/


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## bearintex (Feb 7, 2006)

Quoted from the above link:



> Gah&#8230; people are freakin' stupid.


Pretty much sums it up.:hairout:


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## bk005 (Feb 23, 2005)

Only hinderance a stupid runway size converyor would have on a plane is the the exta thrust required to overcome the extra friction from the wheel bearings due to the wheel speed being X 2. This would be very little. ALthough a Runway size converyor traveling at say 80-100 Mph, Would probably stir up some interesting wind vorticies, this would probably cause the plane more problem, than anyhting else. 

It would be more interesting landing on a giant convyor belt in my opinion.


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## polecat (Jan 21, 2005)

Yes the plane will definitely take off, 110% sure, as has been stated by previous posts, man there are some not so sharp people that really like to argue.


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## Cat O' Lies (May 21, 2004)

da plane! da plane! I see the light now and it will take off! The plane might only be traveling at 100kts, but the wheels on the plane will be "spinning" at 200kts!!!!!


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## Badhabit (May 20, 2004)

bearintex said:


> Quoted from the above link:
> 
> Pretty much sums it up.:hairout:


LMFAO.......True


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## bill (May 21, 2004)

polecat said:


> Yes the plane will definitely take off, 110% sure, as has been stated by previous posts, man there are some not so sharp people that really like to argue.


Is that a science fact, law of physics or thought?

I don't see it as an argue in a bad way, I see a thought process and each of us has tried to put into words our thought. There has been no "ugly or rude" posts. I have a ton of respect for everyone who has taken shot to answer the question.

This is a hugh debate, so many threads on the www and no clear answer. While the laws of physics are on the no fly side, I have yet to see any given law to support the fly. Yes, many good ideas on why it could fly. I don't think it will go away until someone (I hope mythbusters) proves yes/no.


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## speckle-catcher (May 20, 2004)

sorry bill - but the laws of physics are on the side of it flying


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## Badhabit (May 20, 2004)

Get ya one of them rubberband powererd airplanes from the convienience store, find a conveyor, wind the chit outta the plane, set it on the conveyor, let that sucker go and see if it don't fly it's arse off....lol


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## jdkliesing (Nov 9, 2006)

When an airplane takes off, there is one major forward force&#8230; the forward thrust. The main rearward force is air resistance. The turning of the wheels provides a small frictional force, but because the wheels are free-rolling, this friction is very small. Unless the wheels are locked, the friction is always going to be less than the thrust, which means that the overall force is still forward, and the plane will still move.

*Update:* There is a variation on this riddle that says that the conveyor belt matches the speed of the plane. It doesn't matter&#8230; the plane still takes off. The conveyor belt could be going 5 times as fast as the plane, and the plane would still take off. You'd get into issues about tires blowing out, but assuming that the wheels can take the strain, the airplane would still take off.


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## greg77 (May 22, 2006)

polecat said:


> Yes the plane will definitely take off, 110% sure, as has been stated by previous posts, man there are some not so sharp people that really like to argue.


Just out of curuisity, how many engineers have weighed in on this subject.

For the record, I'm one and I don't believe the plane is going to move according to my interpretation of the question. What would happen is that as soon as the brakes are released for takeoff, the conveyor and wheel speed would increase exponentially causing the bearings to melt, causing the wheels to stop turning causing the runway to keep grinding away at the planes landing gear and fuselage untill a spark ignites the spilled fuel causing a massive fire causing me to miss my flight to Vegas.


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## garypro (Dec 1, 2006)

The planes thrust is either jet or propeller not through the wheels. Therefore it woudnt
matter if the conveyor was moving the wheels would just spin faster. The plane will take off. I Hope


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## Too Tall (May 21, 2004)

Don't know about engineers but it was suggested by someones wife that we go stay at a Holiday Inn. Still trying to get a group rate BTW. :smile: 

I'm in the It will fly camp. Others aren't. Don't know of a way that we can realistically prove or disprove it to the other side. Mythbusters couldn't even shoot through a riflescope at point blank range or ignite gas vapors with a non intrinsically safe phone so they won't be any help. Guess we will just have to keep argueing amongst ourselves.


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## bill (May 21, 2004)

Too Tall said:


> Don't know about engineers but it was suggested by someones wife that we go stay at a Holiday Inn. Still trying to get a group rate BTW. :smile:


That was mine. At first I was thinking maybe it would help us (staying in the Holiday Inn). Now I think about it a little more and I think it was directed at me, just to get me out of here for a while and quit wasting time. LOL She is smarter than me, and also being a women, sometimes things have two meanings...LOL

I'm throwing in the towel.......until I get with my b-i-l, he has a couple of them big rc planes.....I just have to figure out a way to build the conveyor belt to keep the plane from rolling. LOL


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## Gottagofishin (Dec 17, 2005)

> A plane is standing on a movable runway(something like a conveyor) As the plane moves, the conveyor moves but in the opposite direction. The conveyor has a system that tracks the speed of the plane and matches it exactly in the opposite direction.


 Now let's really blow some minds. Think about this...

If you think the plane can't take off because is standing still and there is no airflow over the wings.... Then how can the the conveyor be moving at all? If the conveyor is matching the speed of the plane, and the plane's speed is 0 mph, then the conveyor will never move.

Think about that!

Sorry. In a boring meeting today.


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## txjoker (Jun 21, 2005)

If that is the case, then answer this... When a bullet is fired, from a gun that is level, does the bullet rise or fall? I think this answer could be used for this plane debate.



speckle-catcher said:


> sorry bill - but the laws of physics are on the side of it flying


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## JeepnTX (Aug 8, 2006)

I didn't read all 14 pages, and I'm sure someone has already said this, but WOW.

Not everyone thinks that a plane is powered by the wheels, right? The forward movement is created by the engines, not the wheels. The wheels are only there so it can roll from the propulsion of the engines. 

It will take off, simply because the wheels/tires are only there to keep the plane's belly off the ground.


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## jdkliesing (Nov 9, 2006)

JeepnTX said:


> I didn't read all 14 pages, and I'm sure someone has already said this, but WOW.
> 
> Not everyone thinks that a plane is powered by the wheels, right? The forward movement is created by the engines, not the wheels. The wheels are only there so it can roll from the propulsion of the engines.
> 
> It will take off, simply because the wheels/tires are only there to keep the plane's belly off the ground.


Thank you......


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## bogey999 (May 1, 2006)

NO

I have not read all this, but no air over the wing means no lift. (that is a period)


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## JeepnTX (Aug 8, 2006)

bogey999 said:


> NO
> 
> I have not read all this, but no air over the wing means no lift. (that is a period)


You, along with many others, are thinking of the plane as a car.

The propulsion of the engines pushes against the AIR behind the plane, causing it to move forward. The plane doesn't achieve rolling status from the tires. There is no load on the tires except for the weight of the plane. Like I said a few minutes ago, and has been said throughout this whole post, the plane WILL take off, simply because the tires having nothing to do with the plane moving or not moving.

What's worse, guys, is google "Airplane Conveyor Belt". There is a PHSYICS forum that has been arguing this for over 12396823948 pages or something like that.


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## Too Tall (May 21, 2004)

bearintex said:


> A plane is standing on a movable runway(something like a conveyor) As the plane moves*(Lets say 200mph)*, the conveyor moves but in the opposite direction. The conveyor has a system that tracks the speed of the plane and matches it exactly in the opposite direction*(200 mph)*.
> 
> The question is, will the plane take off or not and why, or why not.


Plane flies. More than enough wind over the wing to generate lift.


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## dennis_99 (Feb 27, 2006)

If this is true, why hasn't the military utilized this type of technology???


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## speckle-catcher (May 20, 2004)

utilize it for what? it creates no benefit for getting the plane off the ground any faster


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## Too Tall (May 21, 2004)

dennis_99 said:


> If this is true, why hasn't the military utilized this type of technology???


Why? What advantage would it give them? The current system is working just fine.


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## bogey999 (May 1, 2006)

If the plane is not moving throught the air, there is NO lift. This is not hard. 

There is no airspeed guys, the riddle says so. The explanations on the other sites argue that you can impose airspeed, but the riddle STATES there is none.

"The conveyor has a system that tracks the speed of the plane and matches it exactly in the opposite direction"

That means that there is NO ovecoming of inertia. To an observer, the plane is not moving through the air, the wheels have nothing to do with this. If it is not moving through the air, it ain't flying.

DON"T GIVE UP BILL, reinforcements have arrived!

Bogey 

ps, you could write this so that you 'it flies' guys would be right, but as written, the law of inertia keeps it on the ground with the wheels melting down.


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## goatchze (Aug 1, 2006)

No way is this airplane flying. Period.

No, the wheels are not needed for forward thrust. However, it is wind flowing over/under the wings that generates lift, which is what is needed for flight.

IF the wind was traveling at the speed of the conveyer belt, then YES, the plane would fly.

But the plane is not moving relative to the atmosphere and the earth, and the plane will not fly.

In fact, if the plane needed 150MPH air velocity to take off, and the conveyer belt was moving 150MPH in the wrong direction, the plane would need to be traveling 300MPH with respect to the conveyer belt or 150MPH with respect to the ground/air to take off.

Conversely, if the wind was blowing 150MPH at the airplane and the engines were completely shut off (conveyer belt not moving), that thing would fly like a kite.


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## Too Tall (May 21, 2004)

bogey999 said:


> If the plane is not moving throught the air, there is NO lift. This is not hard.


If the plane is not moving. What speed is the conveyor moving at?


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## goatchze (Aug 1, 2006)

Too Tall,

The plane is not moving relative to the air around the wings (excluding the air traveling through the propeller/jet engine)


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## Cat O' Lies (May 21, 2004)

Back to the dyno theory! Lets say your car is on a dyno! Engine is running at 5000rpm. The dyno is strapped to your car and no matter how fast the cars wheels spin, the car is stationary!! Now, lets connect the front of the car to a chain that is connect to a tow truck (tow truck=jet engine mounted to front of car) and then slam the gas petal down on the tow truck. Is the car still stationary????? Or is it being propelled by the tow truck/jet engine????

There is no direct relationship between the tow truck and the dyno machine!!


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## JeepnTX (Aug 8, 2006)

bogey999 said:


> "The conveyor has a system that tracks the speed of the plane and matches it exactly in the opposite direction"


But what effect does that have on the plane still moving forward? You're right, the conveyor speed DOES match the speed of the plane moving forward... but since the wheels cause little to no drag, what affect would it have on forward movement? The plane would still "accelerate" normally, but the wheels would spin faster. As the plane moved faster, the belt would speed up.

BUT it would still not affect the plane. For the speed of the belt to have ANY influence on the plane's movement, a.) the bearings would have to sieze or b.) the tires would have to blow up. Neither of which are stated in the original riddle...but I guess they could be "imposed" :smile:


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## Too Tall (May 21, 2004)

Again. If the plane is not moving what is the speed of the conveyor belt? ZERO. The plane is not moving.
Now if the plane was moving at 200mph. The conveyor would also be moving at 200 mph. At 200mph the plane has enough wind over the wing to achieve flight.


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## boom! (Jul 10, 2004)

OK, Try this. Put your treadmill against a wall and get running on it as fast as you can. Put your arms out like a plane. Jump straight up. Where ya gonna land, on the treadmill, or smashed into the wall? I say on the treadmill, therefore a ground speed of zero. With a gs of zero how are you going to get the necessary lift?


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## spawningbedassassin (Jul 11, 2006)

It is not moving, though, because the conveyor belt is canceling out any forward progress. No forward progress equals no wind. The more the plane's accelator is pushed, the faster the belt travels in the opposite direction.


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## Cat O' Lies (May 21, 2004)

boomgoon said:


> OK, Try this. Put your treadmill against a wall and get running on it as fast as you can. Put your arms out like a plane. Jump straight up. Where ya gonna land, on the treadmill, or smashed into the wall? I say on the treadmill, therefore a ground speed of zero. With a gs of zero how are you going to get the necessary lift?


What if the treadmill was 2 miles long and you could run like The Bionic Man??
Now strap a jet engine to your arse, and see if you gain forward momentum!


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## bogey999 (May 1, 2006)

OK, let's try it this way.

The plane is not powered up, and is moving BACKWARD on a conveyor belt going 200 MPH. You power up the plane and attempt to take off. Your ground speed would have to be 200 MPH just to keep you from going BACKWARD. Your air speed would be 0. Now, if you decrease your thrust, you are going backward on the belt. If you increase thrust, the belt speeds up to match you. You are not flying.

Now then, if you perceive that the conveyor is just a substitute for a frictionless environment, you would take off easily, but that is not the riddle. I take it that the conveyor is capable of moving the mass of the plane backward. That is how I checked my result.

Bogey


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## jdkliesing (Nov 9, 2006)

boomgoon said:


> OK, Try this. Put your treadmill against a wall and get running on it as fast as you can. Put your arms out like a plane. Jump straight up. Where ya gonna land, on the treadmill, or smashed into the wall? I say on the treadmill, therefore a ground speed of zero. With a gs of zero how are you going to get the necessary lift?


Try putting your bicycle on that tread mill and a rope to the wall, the treadmill can go 100mph holding on to the rope pull yourself forward your not pulling at 100 mph but the tires are spining at that speed you will still go forward as fast as you can pull the rope.


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## fonz (Aug 18, 2004)

*Someone could make alot of $$$$$$$*



JeepnTX said:


> I didn't read all 14 pages, and I'm sure someone has already said this, but WOW.
> 
> Not everyone thinks that a plane is powered by the wheels, right? The forward movement is created by the engines, not the wheels. The wheels are only there so it can roll from the propulsion of the engines.
> 
> It will take off, simply because the wheels/tires are only there to keep the plane's belly off the ground.


Then why are all airports using up all that land needed for runways???
All they "airports" would need are conveyer belts? 
One Belt to take off and one used to land???
Like lots of people said no wind no lift..
Why not just put the plane on blocks and spin the wheels fast enough then the plane will fly off the Blocks...
Just my thoughts..... Maybe I wrong????


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## boom! (Jul 10, 2004)

Cat O' Lies said:


> What if the treadmill was 2 miles long and you could run like The Bionic Man??
> Now strap a jet engine to your arse, and see if you gain forward momentum!


Done. Now when I do, the dang conveyor just speeds up and I am going no where.


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## Cat O' Lies (May 21, 2004)

jdkliesing said:


> Try putting your bicycle on that tread mill and a rope to the wall, the treadmill can go 100mph holding on to the rope pull yourself forward your not pulling at 100 mph but the tires are spining at that speed you will still go forward as fast as you can pull the rope.


B-I-N-G-O!!!!!!!!!! We have a winner!!!!!!!


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## goatchze (Aug 1, 2006)

Check out this awesome diagram!

What matters for lift is the velocity of the airplane w/respect to the air around it. If it is not moving in relation to the air around it, it cannot get any upward forces (caused by air flowing over the wing)

This is why trans-atlantic flights are an hour longer on the way home. The air speed is still the same as the trip over to Europe, but now you're flying into the wind, so the ground speed is less.

The ground speed here is still zero. The conveyer speed is, say, 150MPH. If there is no wind, then wind speed = ground speed.

On the conveyer, no lift. Off the conveyer with the same thrust from the enginers, LIFT!


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## Too Tall (May 21, 2004)

bogey999 said:


> OK, let's try it this way.
> 
> The plane is not powered up, and is moving BACKWARD on a conveyor belt going 200 MPH. You power up the plane and attempt to take off. Your ground speed would have to be 200 MPH just to keep you from going BACKWARD. Your air speed would be 0. Now, if you decrease your thrust, you are going backward on the belt. If you increase thrust, the belt speeds up to match you. You are not flying.
> 
> ...


At 200 mph you don't think theres enough lift generated to get the plane off the ground? You don't transition to airspeed until your in the air.


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## goatchze (Aug 1, 2006)

TooTall,

Air speed is just ground speed + or - the wind.


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## bogey999 (May 1, 2006)

There is NO lift if are not pulling the wings through the air. You are going backward, at 200 mph, by powering forward at 200 mph, you are just making the wind 0mph over the wings, no lift.

The wind was blowing 200 mph forward over the wings until you started the plane, then when you got the plane moving 200 mph, the wind is 0mph over the wing.

Bogey


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## bearintex (Feb 7, 2006)

Good Lord, people! The plane flies! How could it possibly not? The propulsion from the engine is completely, utterly independent of the conveyor. You are still trying to equate the propulsion to that of a car, or animal or other land- based conveyance where the forward force vector must act upon the ground (which is moving with the opposite direction). If the plane used wheel driven propulsion, you would be correct.


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## boom! (Jul 10, 2004)

"As the plane moves, the conveyor moves but in the opposite direction. *The conveyor has a system that tracks the speed of the plane and matches it exactly in the opposite direction."
*
Now where does it say that you are able to "pull on a string" or "increase thrust" and escape the system? To me it says that as you increase thrust (to increase speed) the conveyor matches it in the oposite direction. 
To the dark side, it says "The conveyor has a system that tracks speed and matches it exactly in the opposite direction, UNTIL YOU PULL ON A STRING AND OVERCOME THE CONVEYOR MOVING IN THE OPPOSITE DIRECTION"


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## boom! (Jul 10, 2004)

goatchze said:


> TooTall,
> 
> Air speed is just ground speed + or - the wind.


True statement


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## bogey999 (May 1, 2006)

bearintex said:


> Good Lord, people! The plane flies! How could it possibly not? The propulsion from the engine is completely, utterly independent of the conveyor. You are still trying to equate the propulsion to that of a car, or animal or other land- based conveyance where the forward force vector must act upon the ground (which is moving with the opposite direction). If the plane used wheel driven propulsion, you would be correct.


I dont care if the thing is sitting on a pile of mush with no wheels, if you do not have air going over the wing, you do not get lift. Propulsion method has nothing to do with it.

Bogey


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## Too Tall (May 21, 2004)

boomgoon said:


> "As the plane moves, the conveyor moves but in the opposite direction. *The conveyor has a system that tracks the speed of the plane and matches it exactly in the opposite direction."*
> 
> Now where does it say that you are able to "pull on a string" or "increase thrust" and escape the system? To me it says that as you increase thrust (to increase speed) the conveyor matches it in the oposite direction.
> To the dark side, it says "The conveyor has a system that tracks speed and matches it exactly in the opposite direction, UNTIL YOU PULL ON A STRING AND OVERCOME THE CONVEYOR MOVING IN THE OPPOSITE DIRECTION"


BG we will discuss it further at the range tomorrow. Hows that?


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## Cat O' Lies (May 21, 2004)

As long as the force pushing the plane forward is greater than the force of the wheel friction on the treadmill your going forward!!!


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## bogey999 (May 1, 2006)

Friction does not enter in to the riddle as stated. The conveyor is moving the plane backward as fast as the plane is thrusting forward.

NO LIFT

Bogey


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## boom! (Jul 10, 2004)

Cat O' Lies said:


> As long as the force pushing the plane forward is greater than the force of the wheel friction on the treadmill your going forward!!!


"The conveyor has a system that tracks the speed of the plane and matches it exactly in the opposite direction."

Doesn't this statement cover your statement?


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## Gottagofishin (Dec 17, 2005)

bogey999 said:


> ...There is no airspeed guys, the riddle says so. ...


The riddle doesn't say that at all. Re-read the riddle.


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## Cat O' Lies (May 21, 2004)

LOL! My belly is hurting here from laughter!! This is a side splitter!!! The plane doesn't use it's wheels to take off!!! So who cares what the plane is sitting on? The relationship of the wheels to the treadmill is completely seperate from the relationship its engine has with the surrounding air!


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## bogey999 (May 1, 2006)

Gotta, I think I explained that already - IMO

Bogey


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## JeepnTX (Aug 8, 2006)

Cat O' Lies said:


> LOL! My belly is hurting here from laughter!! This is a side splitter!!! The plane doesn't use it's wheels to take off!!! So who cares what the plane is sitting on? The relationship of the wheels to the treadmill is completely seperate from the relationship its engine has with the surrounding air!


Why is it that noone can understand this?


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## bogey999 (May 1, 2006)

Seems like many of you guys think engines, jets, etc are magic. They just move the mass. If the mass has wings, the mass can fly. The engine does not cause the lift.

Bogey


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## Gottagofishin (Dec 17, 2005)

This is too funny!


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## Cat O' Lies (May 21, 2004)

OK! Try this!! Get on your treadmill and run as fast as you can while you tightly hold a untied balloon full of air in your mouth! You and the balloon are still going nowhere, right? Now let the balloon leave your mouth, where did the balloon go??? Did it just peter out in your mouth or did it fly away???


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## bogey999 (May 1, 2006)

Cat, there is no comparison. Now, if you hold on to the balloon, and let the air out behind you, it adds a micro minute amount of thrust to you, which the riddle says the treadmill can track and will counter.

Bogey


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## Gottagofishin (Dec 17, 2005)

bogey999 said:


> Seems like many of you guys think engines, jets, etc are magic. They just move the mass. If the mass has wings, the mass can fly. The engine does not cause the lift.
> 
> Bogey


You're almost there. The jets (not the wheels) do indeed move the mass regardless of what the treadmill is doing since they are acting against the surrounding air rather than the conveyor.


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## bogey999 (May 1, 2006)

The conveyor is moving the mass of the plane in the opposite direction of the thrust. Newtons laws are not to be trifled with. The plane is not moving through the air. No lift.

Bogey


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## Gottagofishin (Dec 17, 2005)

bogey999 said:


> The conveyor is moving the mass of the plane in the opposite direction of the thrust. Newtons laws are not to be trifled with. The plane is not moving through the air. No lift.
> 
> Bogey


Uncle! LOL!


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## goatchze (Aug 1, 2006)

I'm sure you guys are just yanking our chains, but you're bringing out the nerd in me! Check out the following two FREE BODY DIAGRAMS. All assume NO WIND.

In the first, the airplane is "at rest" with respect to the ground (it is on a conveyer). If it is not moving relative to the Earth, then all forces in the X and Y direction must sum to zero.

In the second diagram, air is flowing over the wings (the plane is NOT on a convyer..uh, sorry, replace the firction due to convyer with friction due to the ground). 

There are two addtional terms. One is the drag due to the air. The second is the lift generated due to air flowing over and under the wings. This addtional force is required to cause the plane to move UPWARD.

Something to note: Since the convyer belt IS moving in the first diagram, and the ground IS NOT moving in the second, then the frictional force due to the ground is MUCH smaller. This is why the plane would move forward on the ground but would remain "at rest" on the convyer.

Without the forward motion causing air to move across the aircraft, then the two terms in the second diagram would not exist. The plane would remain "at rest" and would not move forward, nor would it move upward.

Ok, lay the nerd comments on...


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## goatchze (Aug 1, 2006)

By the way, I just drew the airplane as a circle. It could be a square, or not even be in the diagram. The arrows are all that matter....


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## JeepnTX (Aug 8, 2006)

Nerd!

Even though your diagrams are forgetting about something. Draw a plane attached to the "ball" with the jet engine attached to it. Then add bearings where the plane is attached to the "ball". Then realize that the bearings let the "ball" spin independent of the plane, which causes no added drag to the plane.


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## bearintex (Feb 7, 2006)

bogey999 said:


> The conveyor is moving the plane backward as fast as the plane is thrusting forward.


So what?!! The wheels simply turn twice as fast. Period. The error in your argument is that *the conveyor is moving the plane. *The riddle simply states that the conveyor is moving at a speed to match the plane. Plane moving 100MPH East= conveyor belt moving 100MPH west= wheelspeed of 200 MPH. Note that the plane is *STILL MOVING*. When the plane moves, air is moved over the wings. When air is moved over the wings, lift is created.


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## Too Tall (May 21, 2004)

bogey999 said:


> The conveyor is moving the mass of the plane in the opposite direction of the thrust. Newtons laws are not to be trifled with. The plane is not moving through the air. No lift.
> 
> Bogey


Therfore the conveyor speed is zero. The plane is not moving.


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## rangerjohn (May 15, 2006)

i would say yes the plane could fly 

IF it is one of those heier (sp) arnt those the ones that take off strait up?


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## goatchze (Aug 1, 2006)

JeepnTX...the thrust from the airplane is coming from the engines in that diagram. There are no "bearings" needed. Like I said, all that matters are there arrows, not the fact that I drew a circle (I figured the circle would get people)

There are many terms left out. For instance the wheels have mass, and it takes some force to keep them rotating about. Also,as you mentioned, bearings eliminate the friction required to mechanically roatate the tires.

But no where in the diagram did I talk about tires rotating. Those are all the forces felt by THE ENTIRE AIRCRAFT. You could put the things on skiis for all that it matters, the diagram wouldn't change (ok, maybe the labeling would).


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## Cat O' Lies (May 21, 2004)

goatchze said:


> By the way, I just drew the airplane as a circle. It could be a square, or not even be in the diagram. The arrows are all that matter....


Looks like "fuzzy math" to me! Enron economics!! LOL!!!!


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## Farmer Jim (May 21, 2004)

The plane will fly. Admittedly, there some practical issues (as others have mentioned) such as the heat build-up causing blown tires, seized wheel bearings, or maybe the engine coming apart from an overspeed. But the puzzle is really related to theory, not part failure. The key part of the puzzle is the statement that "The conveyor has a system that tracks the speed of the plane and matches it exactly in the opposite direction." This statement ignores the third variable in getting the plane off of the ground: wheel speed. As long as wheel speed is faster than any opposite speed of the surface that the wheels are on, the plane will move forward through the air.


All of the aerodynamic statements about flight that folks have been posting are essentially correct, but irrelevant. There are three variables in the puzzle: speed of the plane, speed of the conveyor, AND SPEED OF THE WHEELS. The speed of the wheels is what will provide the forward motion that will allow the plane's wings to reach enough forward velocity through the air to attain lift. This is true whether the plane is on a runway or on this conveyor. Only two of the variables, forward speed of the plane and the speed of the conveyor, are directly linked to each other. The speed of the wheels is independent of either of these and is related to thrust (jet ot prop). Therefore, as the forward speed of the plane increases, the conveyor will increase correspondingly. BUT, the speed of the wheels, which is independent of those two linked variables, will increase even more allowing the plane to move forward through the air. Remember, we do not care how fast the plane is traveling on the surface of the conveyor, only how fast the wings are traveling through the air. When it reaches the appropriate airspeed, you will be able to pull back on the yoke and she will leave mother earth.

Only fault I see in any of the "it will fly" posts are the comments about the wheels going twice as fast as the conveyor. I would have to give a little more thought to it, but I'm pretty sure the relationship of the wheel speed on the surface of the conveyor would vary depending on the size of the wheels. I suspect that it could be different multiples depending on the wheel size.


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## goatchze (Aug 1, 2006)

ha ha. Except it matters whether the arrows are point up or down!!!


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## boom! (Jul 10, 2004)

goatchze said:


> JeepnTX...
> There are many terms left out. For instance the wheels have mass, and it takes some force to keep them rotating about. Also,as you mentioned, bearings eliminate the friction required to mechanically roatate the tires. QUOTE]
> 
> Correct, called "sprung weight". For every pound of sprung weight removed from airframe, you can subtract 10 lbs from your power to weight ratio. But do you think that they are ready for that information? LOL


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## DG96 (May 9, 2006)

Glad I didn't go to texas tech!!!



txjoker said:


> Here is a response from one of our science teachers:
> 
> The plane will not take off. To achieve lift, it must have air moving over it's wings. If the air speed is enough (I'm guessing around 100mph for a big heavy jet), then the upward lift will be enough to carry the plane into the sky. In your scenario there is no air moving over it's wings, so no lift is achieved.
> 
> Alternate scenario, using this concept: The plane is sitting still on the ground. A hurricane comes along, with winds over 100mph. Assuming that the winds are hitting the plane head-on, the plane will actually try to lift off of the ground (I don't mean blown around, I mean fly), even though it's engines are off. That's how they test airfoil shapes in wind tunnels. Keep the airfoil still, and blow air over it with a little smoke so that you can see what's going on...


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## goatchze (Aug 1, 2006)

Farmer Jim, I think you're mistaken. The wheels...as a whole...always travel at the same velocity as the airplane. They rotate at such a rate that the surface of the tires are moving across the relative surface at the same rate as the airplane.

But you may be on to something.

The real trick to the riddle lies in whether the convyer surface moves a) at the speed of the airplane relative to the conveyer or b) at the speed of the airplane relative to the ground.

The latter would be impossible and may be the fundamental "catch" of the riddle. That's why I assumed the first.


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## FishDByrd (Mar 23, 2006)

Cat O' Lies said:


> LOL! My belly is hurting here from laughter!! This is a side splitter!!! The plane doesn't use it's wheels to take off!!! So who cares what the plane is sitting on? The relationship of the wheels to the treadmill is completely seperate from the relationship its engine has with the surrounding air!


Well, yes, wheels, skis, pontoon don't matter. What does matter is laminer flow of air over the wings. I am sure you are all aware that the idea of a runway is to allow an aircraft to build forward speed with respect to the air surrounding it not necessarily the ground. The air passing over the wings due to the forward movement of the aircraft (caused by the aircraft's thrust) produces lift which gets the plane off the ground. If there is no forward momentum relative to the surrounding air then the plane will not fly becuase it will not be able to generate lift. Planes have wheels, skis, pontoons so that the can move forward to increase the flow of air over the wings.

The reverse direction of the conveyor cancels out the forward momentum of the wings through the air which results in no air movement over the wings and thus NO LIFT.

Now if this is an F-16 which has jet engine capable thrust exceeding its weight, then a some point it will take off like a rocket (Ballistic flight -> airborne purely due to thrust to weight ratio rather than aerodynamic lift) in which ever direction it is pointing when that thrust level occurs.


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## Blue Water Ho (May 21, 2004)

Man, I need a stiff drink after only "skiming" yalls posts. Uhh my vote is it wont take off, but hell I think I fried most of my brain cells reading some of these post.


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## Farmer Jim (May 21, 2004)

goatchze said:


> Farmer Jim, I think you're mistaken. The wheels...as a whole...always travel at the same velocity as the airplane. They rotate at such a rate that the surface of the tires are moving across the relative surface at the same rate as the airplane.


This is true only if the surface the wheels are moving on is stationary. If the surface is moving (in either direction) the relationships of wheel speed, ground speed and air speed will change. Remember, to attain flight, air speed is the only one of those that matters and its relationship to the others is totally irrelevant.


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## bogey999 (May 1, 2006)

A plane is standing on a movable runway, that means the runway moves, and the controls are such that it moves EXACTLY equal and opposite to the thrust of the engine, therefore no forward movement THRU THE AIR, therefore no lift.

Bogey

Anyone want to go for a discussion of quantum mechanics, or why Einstein was wrong and finally admitted it???


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## bogey999 (May 1, 2006)

A jet is on an aircraft carrier, IN a hurricane. It is a following wind, blowing from the back of the carrier to the front. IT is blowing at 200 MPH. A jet is catapulted off the front of the carrier, with a combined speed of the carrier and the launch system of 200 mph. The airspeed of the plane, launched from this MOVABLE runway is 0 mph and it falls into the sea.

Bogey


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## Farmer Jim (May 21, 2004)

bogey999 said:


> A plane is standing on a movable runway, that means the runway moves, and the controls are such that it moves EXACTLY equal and opposite to the thrust of the engine, therefore no forward movement THRU THE AIR, therefore no lift.
> 
> Bogey
> 
> Anyone want to go for a discussion of quantum mechanics, or why Einstein was wrong and finally admitted it???


Bogey, you keep ignoring the third variable, wheel speed. Air speed is what ultimately provides lift. Until the aircraft is in the air, airspeed is a function of the wheel speed being faster than the surface the wheels are passing over. If there is adequate thrust to provide that wheel speed, the relationship between the conveyor's speed and the plane's speed does not matter. The only thing that matters is the relationship between the speed of the wheels and the speed of the conveyor. If this is greater than 1:1, the plane will move forward through the air. The more it exceeds 1:1, the greater the airspeed and consequently the lift on the wings until finally, enough velocity through the air is attained that will permit takeoff.


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## Gottagofishin (Dec 17, 2005)

Jim,

Your explanation makes perfect sense to me, but if someone didn't understand the skateboard on the treadmill analogy, I don't think they'll get it.

Bogey,

For your aircraft carrier example to be relevent, one would have to assume that somehow the conveyor belt causes the air surrounding the airplane to move at the same speed in the opposite direction.


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## Cat O' Lies (May 21, 2004)

So this is how someone gets thier post count up! LOL!!


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## Farmer Jim (May 21, 2004)

bogey999 said:


> A jet is on an aircraft carrier, IN a hurricane. It is a following wind, blowing from the back of the carrier to the front. IT is blowing at 200 MPH. A jet is catapulted off the front of the carrier, with a combined speed of the carrier and the launch system of 200 mph. The airspeed of the plane, launched from this MOVABLE runway is 0 mph and it falls into the sea.
> 
> Bogey


To solve the puzzle, it is best to assume zero wind. Any head wind or tail wind will alter the relationships between airspeed, groundspeed and wheel speed. However there will be no impact on the principles involved, just on the numbers and their relationships.


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## speckle-catcher (May 20, 2004)

tha damm plane will fly.

I went and asked a former Naval Pilot (and a major engineer nerd) in our office.

his best description was that the *engines of the plane push against air in order to develop forward motion*, so what the ground beneath it does is irrelevant. If the conveyor moves backwards at the same speed the plane makes forward motion, the only thing that means is that the wheels will be spinning at twice the same speed as the plane and conveyor are moving.

I know I said this earlier - but think about it again...

If the plane is sitting still on the conveyor and the conveyor suddenly starts moving - the plane will stay in the same place (assuming all friction losses) - even if you include losses, the plane move only very slightly, but will basically stay in place

so now you have a conveyor moving, but the plane is standing still and the engines are not even running. What is giong to happen when the engines fire up? The plane will move forward. IF the conveyor is moving backwards, the wheels are already spinning that direction at the speed of the conveyor. Now th fuselage of the plane moves forward, taking the wheels with it. The wheels will be spinning at twice the speed the rest of the plane is moving.


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## bogey999 (May 1, 2006)

You guys are just plain missing it. The riddle says the runway moves. That means the runway moves. If the runway moves 200 MPH West and the plane thrust is adequate to equal that in the opposite direction (east) , the plane has no airspeed. No lift.

and please lets forget about the wheels ! They are not a factor

Bogey


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## bearintex (Feb 7, 2006)

bogey999 said:


> A plane is standing on a movable runway, that means the runway moves, and the controls are such that it moves EXACTLY equal and opposite to the thrust of the engine, therefore no forward movement THRU THE AIR, therefore no lift.
> 
> Bogey
> 
> Anyone want to go for a discussion of quantum mechanics, or why Einstein was wrong and finally admitted it???


:headknock :headknock :headknock :headknock


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## txjoker (Jun 21, 2005)

Who said anything about our science teachers going to TTU? I am a school teacher. Actually, the teacher that wrote that is an Aggie. lol Go figure.



DG96 said:


> Glad I didn't go to texas tech!!!


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## bogey999 (May 1, 2006)

bearintex said:


> :headknock :headknock :headknock :headknock


Just saying it flies, or that I am wrong does not support the riddle, WHY do you think it flies, no answer so far by anyone except faith in others opinions, or "Of Course, It Just Will"

The runway is MOVING, forget the wheels, forget 'conveyor', it is moving.

The aircraft carrier is a perfect example. If it goes backward as fast as the catapult and engine of a jet push forward, the plane is going in the water.

That is why carrier typically turn into the wind to launch, it used to be absolutely necessary. Not so much now, but you still take every advantage 
you can.

Now, if you can prove to me that that plane will fly, git-r-dun

Bogey


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## Farmer Jim (May 21, 2004)

bogey999 said:


> You guys are just plain missing it. The riddle says the runway moves. That means the runway moves. If the runway moves 200 MPH West and the plane thrust is adequate to equal that in the opposite direction (east) , the plane has no airspeed. No lift.
> 
> and please lets forget about the wheels ! They are not a factor
> 
> Bogey


LOL! Bogey, they are the *ONLY* factor. It is the relationship between the wheel speed and the speed of the surface that they are on that will determine how fast the plane moves through the air. This is true whether the surface is stationary (a runway) or a conveyor moving in either direction.

Think of it as a math problem with the answer (unknown) being airspeed.

Airspeed = wheel speed minus surface speed.

Assume a wheel speed of 200.

If the surface is stationary: 200-0=200 airspeed

If the surface is a conveyor moving backwards at 100: 200-100=100 airspeed

If the surface is a conveyor moving forward at 100: 200-(-100)=300 airspeed


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## Flyboy (Oct 3, 2004)

Ok, Think of it this way&#8230; 



You are standing beside a conveyer belt. On the belt is a shopping cart from HEB. (I didn't take it TOO TALL did). You place your hand on the back of the shopping cart and push it forward at 10mph. You are now walking beside the belt at 10 mph. The belt moves in the opposite direction at 10 mph. The wheels on the shopping cart are now doing 20 mph. YOU ARE STILL MOVING FORWARD AT 10! The belt can move as fast as it wants I can still move the shopping cart and walk beside the belt. The wheels on an aircraft spin freely just like the shopping cart. (Actually more freely, they are greased and have wheel bearings unlike the shopping cart.) Your arm is the same as the engines (prop or jet). The thrust for forward movement in an aircraft is from the engines pushing against air, it has nothing to do with the wheels. 



Take off speed varies with weight. Just for a round number say that a 737 takeoff speed is 150 knots. The conveyor belt would be moving in the opposite direction at 150. The wheel speed would be 300. You are now going to have major problems because the tire speed limit on a 737 is 195 knots! You just had six explosions when your tire speed exceeded their limits and now you are dragging the wheel struts on the belt. Now some of you are wondering why I said six explosions. Each strut has two tires. 



Yes, I did stay at a Holiday Inn last night!


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## bogey999 (May 1, 2006)

No farmer Jim, the wheels are not important. Air speed is important ONLY

Airspeed = Speed through air and there is none

Assume again that the plane is being carried backward at 200 mph

Assume the engine has thrust to move the plane forward to exactly overcome the movement of the conveyor.

the airspeed is 0

Bogey


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## speckle-catcher (May 20, 2004)

the plane will never move backward


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## Farmer Jim (May 21, 2004)

bogey999 said:


> Now, if you can prove to me that that plane will fly, git-r-dun


You are too hung up on aerodynamics. Aerodynamics are only remotely related to solving the puzzle. No one disputes that a cetain airspeed is required to generate adequate lift on the airfoil. The puzzle relates to whether the plane can attain that airspeed on the conveyor. The thing to remember is what I said earlier. Until a plane leaves the ground, the airspeed is determined by the relationship of the wheel speed over the surface that the wheels are on. How the wheels attain that speed is also immaterial as long as there is a thrust source adequate to move the aircraft at a speed faster than the surface is moving.

You are in what is known as a locked paradigm. Move your mind to the correct velocity and let it fly.


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## boom! (Jul 10, 2004)

Well if Farmer Jim can get an eggbeater to fly, and he says it'll fly, I submit. I guess that it will fly!


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## bogey999 (May 1, 2006)

Flyboy said:


> Ok, Think of it this way&#8230;
> 
> You are standing beside a conveyer belt. On the belt is a shopping cart from HEB. (I didn't take it TOO TALL did). You place your hand on the back of the shopping cart and push it forward at 10mph. You are now walking beside the belt at 10 mph. The belt moves in the opposite direction at 10 mph. The wheels on the shopping cart are now doing 20 mph. YOU ARE STILL MOVING FORWARD AT 10! The belt can move as fast as it wants I can still move the shopping cart and walk beside the belt. The wheels on an aircraft spin freely just like the shopping cart. (Actually more freely, they are greased and have wheel bearings unlike the shopping cart.) Your arm is the same as the engines (prop or jet). The thrust for forward movement in an aircraft is from the engines pushing against air, it has nothing to do with the wheels.
> 
> ...


That is a very good analogy, except...

From your point of view you are going 10mph, but from the point of view of the riddle, ie the plane, you are standing still. From the point of view of the conveyor, you are going 20 mph. You injected yourself into the exercise as an outside force, and that cannot be. You would have to climb into the cart and blow backward real hard, in and effort to move the cart, then your analogy is valid. The speed of the runway and the airplane relative to each other must be 0, according to the rules

Bogey


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## bogey999 (May 1, 2006)

Farmer Jim, lol

The question is, will the plane take off or not and why, or why not.

That is kinda aerodynamic

Bogey


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## speckle-catcher (May 20, 2004)

sorry Bogey - his analogy is the closest one that has been made that describes the riddle.

the plane will never move backward on the conveyor as you stated.

the plane flies.


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## bogey999 (May 1, 2006)

Farmer Jim said:


> Until a plane leaves the ground, the airspeed is determined by the relationship of the wheel speed over the surface that the wheels are on.


No no no

Airspeed is determined by the speed of the air over the airfoil, has nothing to do with the surface speed, or the speed relative to any other surface.

a parked plane can take off if you set a fan in front of it to generate lift, or call up a hurricane

Bogey


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## speckle-catcher (May 20, 2004)

bogey - yer gonna hafta to learn to type faster :rotfl:


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## Flyboy (Oct 3, 2004)

bogey999 said:


> You injected yourself into the exercise as an *outside force*, and that cannot be. You would have to *climb into the cart and blow backward real hard*, in and effort to move the cart, then your analogy is valid. Bogey


That is exactly what I was trying to do... The engines on the aircraft are an outside force from the belt. Say I did climb in that cart and strapped a Tomahawk missile on my back..... Is that blowing backward enough for you! The wheels can go as fast as they want and melt off the shopping cart. The missile is still going to find its target.


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## bogey999 (May 1, 2006)

speckle-catcher said:


> sorry Bogey - his analogy is the closest one that has been made that describes the riddle..


I AGREE!!!

That is the best analogy to explain why you guys are locked into the wrong answer 

"the plane will never move backward on the conveyor as you stated."

Of course it can move backward, it is on a "movable" runway!!

Bogey


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## ANGEL (May 21, 2004)

ok who has a airplane we can borrow and a conveyer deal we can use


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## bogey999 (May 1, 2006)

Flyboy said:


> That is exactly what I was trying to do... The engines on the aircraft are an outside force from the belt. Say I did climb in that cart and strapped a Tomahawk missile on my back..... Is that blowing backward enough for you! The wheels can go as fast as they want and melt off the shopping cart. The missile is still going to find its target.


Rockets not allowed, we are using wings here!

LOL

Bogey


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## greg77 (May 22, 2006)

I'm still firmly in the no-fly zone, but to be fair, I have rephrased the question to better define my interpretation and E-mailed it to my girlfriend who happens to be a Southwest Airlines flight attendant. She has promised to get her pilots to take a stab at it. 
My re-worded question:

A Boeing 737 is on a movable runway of infinite length (something like a conveyor). There is no wind. The runway/conveyor has a system that tracks the speed of rotation of the planes wheels. The conveyor automatically moves in a direction from the front to the back of the aircraft at a speed that EXACTLY matches the rotational velocity of the tires where they contact the movable runway. The plane is prepared to take off (engines are throttled up and the brakes are locked).

The question is, when the brakes are released, will the plane take off or not and why, or why not.


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## Flyboy (Oct 3, 2004)

greg77 said:


> my girlfriend who happens to be a *Southwest Airlines flight attendant. She has promised to get her pilots to take a stab at it. *


Youv'e got to be kidding me those guys are clueless...


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## bogey999 (May 1, 2006)

Now that could change some factors

NO, the conveyor is moving the plane backwards as fast as the engines are pushing forward, no airspeed, no flight

Bogey


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## speckle-catcher (May 20, 2004)

the plane will not move backwards on the conveyor.

the wheels are free-spinning, meaning they are not connected to a driveshaft of any kind, so they are free to move in either direction (clockwise or counter-clockwise) when acted on by an outside force.

of course, we ignore friction at the axle in order to simplify

the plane is held in place by it's own mass. The force (F=M*a, not "The Force" as in Star Wars) acts straight downward due to gravity. 

once the conveyor starts moving, the wheels will spin, but plane stays put. 

it will stay put until acted on by some outside force. It doesn't matter if the conveyor moves at 1 mph or 100 mph. Those tires are going to be spinning, and the plane ain't moving.

you can prove for yourself. put a skateboard on a treadmill (that is turned OFF). Stand on the skateboard. Turn on the treadmill. You will move slightly due to friction in the wheel bearings. You will move in the same direction as the treadmill is turning, but you won't move at near the speed of the treadmill. If you had perfect frictionless bearings - you would never move.


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## bogey999 (May 1, 2006)

speckle, if I put you on a conveyor, you are gonna move, who said no friction, that mass will move

Bogey


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## Mako Mike (Jun 8, 2006)

Yes the plane will take off. Because the props (assuming this is a prop plane) are made to displace air for thrust. When the prop spins at some rpm it = some amount of thrust relative to the air. As air speed is what it needed to take off, ground speed of the tires don't matter, maybe a slight bit of additional drag, but it would be negligable as those wheels would just be freespinning.

Now if the pilot where standing on the brakes or the ground cerw didn't take out the chocks... different story. Then you better have one awefully long convery belt or someone is getting flipped!


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## Farmer Jim (May 21, 2004)

greg77 said:


> The question is, when the brakes are released, will the plane take off or not and why, or why not.


Nope. This one is a no fly. As long as the rearward velocity of the conveyor matches the speed at which the wheels are turning, the plane will be stationary and the airspeed will be zero.


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## txjoker (Jun 21, 2005)

So, are you back on the side of "No Fly"?



speckle-catcher said:


> the plane will not move backwards on the conveyor.
> 
> the wheels are free-spinning, meaning they are not connected to a driveshaft of any kind, so they are free to move in either direction (clockwise or counter-clockwise) when acted on by an outside force.
> 
> ...


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## speckle-catcher (May 20, 2004)

bogey999 said:


> speckle, if I put you on a conveyor, you are gonna move, who said no friction, that mass will move
> 
> Bogey


a person on a conveyor - yes. a person on a skateboard on a conveyor...NO

try it for yourself.


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## bogey999 (May 1, 2006)

Farmer Jim said:


> Nope. This one is a no fly. As lonmg as the rearward velocity of the conveyor matches the speed at which the wheels are turning, the plane will be stationary and the airspeed will be zero.


That has been my position throughout, what is the diff?

Bogey


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## speckle-catcher (May 20, 2004)

TXJ - no- that plane is still gonna fly


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## Farmer Jim (May 21, 2004)

bogey999 said:


> No no no
> 
> Airspeed is determined by the speed of the air over the airfoil, has nothing to do with the surface speed, or the speed relative to any other surface.
> 
> ...


Bogey, you have to get away from the aerodynamics.:headknock That is why I said to ignore wind. The puzzle is not whether planes fly at certain airspeeds. It is whether the plane can attain that airspeed given the variables in the problem.


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## bogey999 (May 1, 2006)

speckle-catcher said:


> a person on a conveyor - yes. a person on a skateboard on a conveyor...NO
> 
> try it for yourself.


You are so close to understanding!

Now if i get ON THE CONVEYOR behind you and push, will we ever move, if the conveyor is capable of speeding up to match our efforts??

Bogey


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## Flyboy (Oct 3, 2004)

bogey999 said:


> Rockets not allowed, we are using wings here!
> 
> LOL
> 
> Bogey


Yes, you are correct the wings will provide the lift to fly. :brew:

There are four forces that act on an airplane.

Thrust - Drag - Lift - Weight

There is no way that the friction from the wheels would be enough drag to overcome the thrust. Once the thrust is greater than the drag the aircraft will accelerate.


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## bogey999 (May 1, 2006)

Farmer Jim said:


> Bogey, you have to get away from the aerodynamics.:headknock That is why I said to ignore wind. The puzzle is not whether planes fly at certain airspeeds. It is whether the plane can attain that airspeed given the variables in the problem.


and it cannot, 

Bogey


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## txjoker (Jun 21, 2005)

But you said to take friction out of the mix. You said it yourself right here. To me, that is a "No Fly" admission.











speckle-catcher said:


> put a skateboard on a treadmill (that is turned OFF). Stand on the skateboard. Turn on the treadmill. You will move slightly due to friction in the wheel bearings. You will move in the same direction as the treadmill is turning, but you won't move at near the speed of the treadmill. If you had perfect frictionless bearings - *you would never move*.


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## bogey999 (May 1, 2006)

Flyboy said:


> Yes, you are correct the wings will provide the lift to fly. :brew:
> 
> There are four forces that act on an airplane.
> 
> ...


But the riddle says that the runway will always move fast enough in reverse to overcome ANY acceleration

Bogey


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## greg77 (May 22, 2006)

Flyboy said:


> Youv'e got to be kidding me those guys are clueless...


Could be but it will be interesting anyway. What we really need is a physicist. I've been out of engineering school a little to long to remember exactly all that book learnin.


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## goatchze (Aug 1, 2006)

Farmer Jim said:


> This is true only if the surface the wheels are moving on is stationary. If the surface is moving (in either direction) the relationships of wheel speed, ground speed and air speed will change. Remember, to attain flight, air speed is the only one of those that matters and its relationship to the others is totally irrelevant.


Sorry, I had to drive home...

This is true ANY TIME the wheels are not skidding. If the wheels are not sliding, then the surface of the wheel is traveling at the same speed as the surface of the treadmill. (In the X direction)


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## speckle-catcher (May 20, 2004)

no - I understand. You are the one that is close.

assume I stand on that skateboard, and the treadmill is running at 2mph...

you come along and push me (hands off my booty you queer  ) - it doesn't matter how fast you push me - I will make forward motion. The treadmill could be running at 100mph backwards and you can still push me forward at 3 mph.

the rotational motion of the wheels is independant of the forward motion applied by an outside force.


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## Farmer Jim (May 21, 2004)

bogey999 said:


> That has been my position throughout, what is the diff?
> 
> Bogey


The difference it that in this problem he said the speed of the conveyor is directly linked to the speed at which the wheels are turning, not to the forward speed of the plane as the original puzzle said.


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## Flyboy (Oct 3, 2004)

bogey999 said:


> But the riddle says that the runway will always move fast enough in reverse to *overcome ANY acceleration*
> 
> Bogey


*No it did not...*

Shamelessly stolen from another message board I frequent, this riddle has gotten over 250 replies in just acouple of days.

The riddle:

A plane is standing on a movable runway(something like a conveyor) As the plane moves, the conveyor moves but in the opposite direction. The conveyor has a system that tracks the speed of the plane and matches it exactly in the opposite direction.

The question is, will the plane take off or not and why, or why not.


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## Farmer Jim (May 21, 2004)

bogey999 said:


> But the riddle says that the runway will always move fast enough in reverse to overcome ANY acceleration
> 
> Bogey


No it doesn't. It says that the conveyor always moves at the same speed as the forward motion of the plane. Big difference.


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## speckle-catcher (May 20, 2004)

txjoker said:


> But you said to take friction out of the mix. You said it yourself right here. To me, that is a "No Fly" admission.


I said ignore the frictional loss at the axle/wheelbearing. for our purposes all it does is complicates the "math"

in the real world there will be frictional loss, but it is so small that it is almost insignificant.


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## bogey999 (May 1, 2006)

speckle-catcher said:


> no - I understand. You are the one that is close.
> 
> assume I stand on that skateboard, and the treadmill is running at 2mph...
> 
> ...


The riddle DEFINES THE RULE that no matter how hard we push, it goes backward just fast enough so we don't move, no airflow, no lift, no fly

Bogey


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## Slip (Jul 25, 2006)

Planes fly from differential pressure from above and below the wing to give a plane lift. Same as a sailboat. If you put a fan on a sailboat, pushing against the sail, it will not sail. It takes the vacuum of the wing to give lift, not the engine. The engine gives enough speed to get this wing lift to work. If a high enough comming across the wing, it would lift with or without engine, it just takes the engine to sustane the speed once the plane leaves the ground. Remember the movie Pearl Harbor with the Dolittle raid of getting enough room to get speed up enough to create the lift of getting plane to not fall? Probably wrong and is a trick question, but that is how I see it anyway.


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## Blue Water Ho (May 21, 2004)

Thi is so amusing. But hey guys, whats the meaning of life?


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## bogey999 (May 1, 2006)

Farmer Jim said:


> No it doesn't. It says that the conveyor always moves at the same speed as the forward motion of the plane. Big difference.


It says it will compensate for changing speed, any change in speed is acceleration, either positive or negative

Bogey


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## speckle-catcher (May 20, 2004)

bogey - you anaylsis would be correct if it were a car that was driven on the conveyor


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## speckle-catcher (May 20, 2004)

Blue Water Ho said:


> Thi is so amusing. But hey guys, whats the meaning of life?


dunno - but the answer is 42


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## txjoker (Jun 21, 2005)

I'm still on the "No Fly" side. I have to go, but will be back later. It should not matter how much I push you because the treadmill will always be accelerating as well. You're still not going forward. It still will stay zero. The outside force you speak of I don't consider outside. The engines? The way I understand the riddle, the plane and the treadmill begin at the same time. Where is the outside force? The airspeed? There is none because there is no forward progress.



speckle-catcher said:


> no - I understand. You are the one that is close.
> 
> assume I stand on that skateboard, and the treadmill is running at 2mph...
> 
> ...


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## Farmer Jim (May 21, 2004)

goatchze said:


> Sorry, I had to drive home...
> 
> This is true ANY TIME the wheels are not skidding. If the wheels are not sliding, then the surface of the wheel is traveling at the same speed as the surface of the treadmill. (In the X direction)


Correct. However, assuming that we are going to skid the wheels is something that we are probably safe leaving out of it. If not we have to also start considering full locking of the wheels and partial locking of the wheels.:spineyes:


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## speckle-catcher (May 20, 2004)

ya'll are gonna make me dig out a dynamics book and I don't want to do that. The worst engineering class I ever took.


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## bogey999 (May 1, 2006)

speckle-catcher said:


> dunno - but the answer is 42


AGREED

Bogey


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## Slip (Jul 25, 2006)

Come to think about it, if you were to get on a treadmill and run as fast as you can, do you feel a strong wind against your hair blowing, nope. No speed, no wind, no lift. Putting a car on rollers and putting a car in drive and floor it, the speedometer goes high, but still no movement. Same for the plane. Wheels are onlyh free spinning and will turn as needed but that don't get you anywhere.


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## Flyboy (Oct 3, 2004)

There was once a guy in a small corporate jet that took off from up north on an ICE covered runway with the parking break set. He found out when he got to Houston and landed with the breaks set. His wheelspeed at takeoff and landing was 0. Wheelspeed has nothing to do with airspeed. Airspeed is what provides lift over a wing.


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## Blue Water Ho (May 21, 2004)

speckle-catcher said:


> dunno - but the answer is 42


Ahh ok. I see my problem now I forgot to carry the 3.


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## speckle-catcher (May 20, 2004)

SK - a car moves forward by pushing backwards on the ground...a plane moves forward by pushing backwards on the surrounding air.


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## bill (May 21, 2004)

No meaning to life...there is only life.

What if we took the wheels and belt out. Could a plane sitting on it's belly generate enough force to take off. Like a kite?
(again, the plane can not move forward)


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## Farmer Jim (May 21, 2004)

Bogey, maybe this will help. Whe I am using the term wheel speed, I do not nean the speed at which the wheels are moving over the ground. I mean the speed at which they are turning, eg. rpm expressed as mph.


Fixing to go out to eat. Ya'll keep working on this  till I get back . I figure about another two hours and the emergency admits at the mental wards will start increasing.


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## bogey999 (May 1, 2006)

speckle-catcher said:


> bogey - you anaylsis would be correct if it were a car that was driven on the conveyor


Yes grasshopper, you are coming to the light.

There is no difference. No matter what pushes the mass, if it cannot move relative to the air, it ain't flying

Bogey


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## speckle-catcher (May 20, 2004)

bill - probably if it can ovecome the tremendous amount of friction that would be generated between the under-fuselage and the runway without creating enough heat and sparks to light a fire.

if it was on a conveyor - probably not, unless you assume a perfectly frictionless environment.


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## speckle-catcher (May 20, 2004)

bogey999 said:


> Yes grasshopper, you are coming to the light.
> 
> There is no difference. No matter what pushes the mass, if it cannot move relative to the air, it ain't flying
> 
> Bogey


that's my point - the plane moves relative to the air surrounding it. It doesn't matter what the ground underneath is doing.


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## bill (May 21, 2004)

speckle-catcher said:


> bill - probably if it can ovecome the tremendous *amount of friction that would be generated between the under-fuselage and the runway without creating enough heat and sparks to light a fire.*
> 
> if it was on a conveyor - probably not, unless you assume a perfectly frictionless environment.


no no...the plane can not move...the plane must generate power on it's own to just lift off.


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## bogey999 (May 1, 2006)

gotta work for a while and cook for hours, later guys

Bogey


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## speckle-catcher (May 20, 2004)

bill said:


> no no...the plane can not move...the plane must generate power on it's own to just lift off.


sorry - misunderstood your question.

only if the engines moved to a vertical or near vertical position like a Harrier or an Osprey


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## goatchze (Aug 1, 2006)

So here's an analogy. If i'm running on a treadmill with a hang glider, and then jump into the air....will I fly..Will I do anything besides land just where I jumped and get major treadmill burn on my face, all twisted up in my stupid hang glider?

Nope.

When it comes to lift, it makes NO BEARING what speed the wheels are moving relative to the ground. The only thing that matters is the AIR moving across the wings.

Maybe I've misunderstood the problem...but I thought we were talking about an airplane that was sitting still relative to the ground, that was moving relative to the treadmill. If this is the case, then no amount of accelaration/decelaration or velocity is going to make the airplane fly.

Maybe I should answer like my grandpa would..."What the H_LL is the airplane doing on a G__D_MN convyer belt anyway?"


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## speckle-catcher (May 20, 2004)

alright boys - I gotta head home.

by the time I get back here later, I want ya'll to have figured out that the plane WILL fly


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## bill (May 21, 2004)

speckle-catcher said:


> sorry - misunderstood your question.
> 
> only if the engines moved to a vertical or near vertical position like a Harrier or an Osprey


ok, lets take the next step.

If the belt voids all thrust thru the wheels...now it's the same as if both were gone. If a plane sitting on it's belly can not generate enough power to just "lift off"...........then can we say it will not fly?


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## bill (May 21, 2004)

and I was the first to say unless it's a harrier or other type to produce 20,000+ pounds of vertical thrust....now your back with me on page 2 (my first post) LOL


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## bill (May 21, 2004)

I should hard delete this thread, send SC a message the problem was solved and everyone agreeded...LOL That would mess with him.


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## goatchze (Aug 1, 2006)

Ok, I started to post this long ago but deleted it to respond to Jim.

The plane will never take off of the conveyer, because the conveyer belt cannot exist.

Figure that one out.


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## Too Tall (May 21, 2004)

Mayday, Mayday, Mayday This 2cool fishing declaring a physics emergency.
Too Late.

*Eject, Eject, Eject.

*It's been fun. I'll try and catch up on the rest of this thread later. To see who does and does not solve the mystery.*

BTW. The **** plane flies. 
*


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## scudrunner (May 21, 2004)

Jeez, after 38 years of flying and engineering (flight instructor, standardization flight instructor, airline pilot, degree in aeronautical, instructing in aerodynamics, orbital mechanics and all around air and space stuff), I've just realized how much I don't know about airplanes, conveyor belts and how airplanes fly!


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## goatchze (Aug 1, 2006)

<Hint, there's an impossible specification in the riddle>


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## bill (May 21, 2004)

If no one minds, I am going to go ahead and lock the thread...then in the am delete it. It's using a lot of space and we will not solve it soon. I have access to a large rc plane and if we can come up with a way to make the belt, lets do the test.


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## Badhabit (May 20, 2004)

bill said:


> If no one minds, I am going to go ahead and lock the thread...then in the am delete it. It's using a lot of space and we will not solve it soon. I have access to a large rc plane and if we can come up with a way to make the belt, lets do the test.


Lock it, delete it, or whatever.... But the plane will fly, the ground has nothing to do with an airplane's thrust, lift, or drag, the AIR provides propulsion from the prop, the conveyor has absolutly nothing to do with the AIR, the plane will still pull thru the AIR as long as the wheels are free spinning, because the AIR ain't moving, and the denser the AIR the more pull the plane will have, cold AIR is denser... The AIR, The AIR, THE AIR, thats why it's called an AIRplane..... I don't care if the conveyor is spinning a thousand miles an hour, the AIR above it is still neutral, and the prop pulls the plane thru that neutral AIR which moves the plane forward until takeoff speed is attained, which is about 35 ias "instrument air speed" in a 150 Cessna with 40 degrees of flaps........ Get over it non belivers, the AIR is used as propulsion, not the ground and or conveyor....... Planes don't have a driveshaft to power the wheels, the wheels are FREESPINNING, therefore it don't matter how fast the conveyor turns, THE PROPELLER WILL PULL THE PLANE THRU THE AIR.....


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