Final answer to the airplane on a long treadmill problem ...

[ShooterMcGavin]

Look at it this way: if the plane was in the air and YOU were making the wheels on the plane spin, would the plane fall out of the air? That's all that the treadmill is doing...spinning the wheels. NOTHING MORE.

Look at the diagram again and you will understand why the wheels spin at the plane's forward speed + the treadmill's speed:

can't see the pic cuz it's being blocked by websense but i understand what you're saying and even though i don't think i'm expressing it correctly, what i'm saying is what you're saying

and to hopefully prove that i do fully comprehend, here's a simple followup question that you can easily answer: would it be possible to have/build a treadmill that will move/accelerate in a manner in which it will actually keep the plane in the same spot and grounded?

[Ruiner]

can't see the pic cuz it's being blocked by websense but i understand what you're saying and even though i don't think i'm expressing it correctly, what i'm saying is what you're saying

and to hopefully prove that i do fully comprehend, here's a simple followup question that you can easily answer: would it be possible to have/build a treadmill that will move/accelerate in a manner in which it will actually keep the plane in the same spot and grounded?

As long as the wheels are free rolling (neutral), no, not really. There is a small amount of friction in the wheel bearings. If the plane's thrust matches that friction, exactly, then the plane will stay stationary. Once the plane's thrust passes that friction amount, the plane will move forward.

[ShooterMcGavin]

As long as the wheels are free rolling (neutral), no, not really. There is a small amount of friction in the wheel bearings. If the plane's thrust matches that friction, exactly, then the plane will stay stationary. Once the plane's thrust passes that friction amount, the plane will move forward.

but the key is, what if said treadmill can accelerate constantly? F=ma, so whatever force is provided by engines, it can be equally matched and exceeded by the treadmill if it has enough acceleration, no?

[ShooterMcGavin]

but the key is, what if said treadmill can accelerate constantly? F=ma, so whatever force is provided by engines, it can be equally matched and exceeded by the treadmill if it has enough acceleration, no?

ruiner? anything?

[Ruiner]

ruiner? anything?

The treadmill matches the SPEED of the plane, not the thrust. The tread mill can be moving at 100,000knots while the plane is going at 100knots. It WOULD NOT matter. It would ONLY make the wheels spin at 100,100knots. NOTHING MORE. Guys, the wheels would spin faster, but that would not change the thrust up the engines.

The treadmill in NO way can counteract the THRUST of the engines.

[speedminded]

The treadmill matches the SPEED of the plane, not the thrust. The tread mill can be moving at 100,000knots while the plane is going at 100knots. It WOULD NOT matter. It would ONLY make the wheels spin at 100,100knots. NOTHING MORE. Guys, the wheels would spin faster, but that would not change the thrust up the engines.

The treadmill in NO way can counteract the THRUST of the engines.

lemme help you out with the porsche on the dyno analogy....imagine a vehicle on the dyno in neutral...the wheels are free spinning just as a planes wheels are. Now imagine if that car was not strapped down on the dyno, it should remain free wheeling on top of the rollers even if power were applied to the dyno (like a treadmill) in turn causing the wheels to spin. Ok so now you would have a car sitting there with wheels spinning but not going anywhere (ever seen anyone spin 2 basketballs on top of each other or a man running on a floating barrel or log in the water?) Same idea, one causes the other to spin but since the bottom one is stationary neither go anywhere.

Anyways, back to the car on the dyno...it's not strapped down and no power is being supplied to the wheels. Now imagine if you had 4 people or even just one person run and push the back of the vehicle...is the car still going to go forward? yes. Now if you turn on the engines of the plane is it going to go anywhere? yes.

[Vteckidd]

Anyways, back to the car on the dyno...it's not strapped down and no power is being supplied to the wheels. Now imagine if you had 4 people or even just one person run and push the back of the vehicle...is the car still going to go forward? yes. Now if you turn on the engines of the plane is it going to go anywhere? yes.

EGGSFUCKINGZACTLY

[ShooterMcGavin]

The treadmill matches the SPEED of the plane, not the thrust. The tread mill can be moving at 100,000knots while the plane is going at 100knots. It WOULD NOT matter. It would ONLY make the wheels spin at 100,100knots. NOTHING MORE. Guys, the wheels would spin faster, but that would not change the thrust up the engines.

The treadmill in NO way can counteract the THRUST of the engines.

correct, that's not what i was saying and i'm acknowledging this is a departure from the original question. the followup question involves whether or not a treadmill could be designed to match the FORCE (or acceleration) of the plane. in which case, wouldn't the answer be yes?

[swiftblaze]

In regards to Echo's post,

The remote control plane idea is flawed because it needs to travel a longer distance in order to generatete enough lift to take off. I can guarantee you that the plane will move forward. As stated earlier, stand on a treadmill with rollerskates and hold on to the front bar. Set the treadmill to a high setting and attempt to pull yourself forward. You will be able to very easily. This contradicts your previous statements stating that the "plance" will not move forward. The wheels are freely spinning and do not affect the thrust pushing the plane forward. A remote control plane will move forward on the treadmill fine, but it does not have near enough distance to take off. On the other hand, a treadmill the size of a runway will provide adequate distance for a plane to be able to take off.

I have an interesting idea. This same giant treadmill can be used in the car scene as well. If you place a car on a treadmill while in neutral and attach a jet engine in the trunk, will it move forward? Yes! The wheels are not providing any power whatsoever. The jet engine mounted in the trunk of the car will push the car foward against the treadmill since the wheels are only acting as a contact point between the car and the ground. The car can gain quite a bit of speed as well. Now, image if you have an airplane capable of producing twice the amount of thrust as that single jet engine mounted in the back of the car. Understand where I am coming from? The wheels are merely a contact point and are needed to provide control and reduce friction. A plane would not be able to take off very well on a runway while resting on its belly. The free spinning parts allow for this to happen. However, a plane will be able to take off on ice without landing gear. The ice will not provide enough resistance to prevent the plane from taking off or catching on fire. Hell, planes take off from water all the time without landing gear.

I have another interesting idea to consider. Let's say you replaced the wheels of the plane with a flat surface the provides no friction whatsoever. Will the plane move forward with the engines at full throttle? YES! The treadmill will spin freely under this "frictionless" material and will not effect the speed of the plane moving forward. I know this is a lengthy response, but I hope this will eliminate some of the doubts from others who are skeptical about the whole plane vs. treadmill idea. Next time you go to an airport with motorized walkways, bring some rollerskates and hold on to the railing. Then, have a friend behind you try to push you the opposite direction of the motorized sidewalk. You will receive many crazy looks, but you WILL move forward.

This is just my on this question.

Chris