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Plane on a Treadmill

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wolverine68

wolverine68

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mjlane

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wolverine68 said:
If in fact the treadmill could run faster than the plane, then the plan would crash off of the back of the treadmill because (just like the matchbox car) it could not achieve lift..
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No. If the belt was travelling 100mph and the plane was generating enough thrust to travel 100mph, then the plane will move forward at 100mph relative to the ground (a little less when you account for friction). Increasing the belt speed will not affect the forward speed of the plane.
 
CycloneWanderer

CycloneWanderer

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the thrust from a jet is acting on the air around the plane, not the treadmill - the air is not moving until the jets act upon it which is independent of the treadmill. With that said I think it would be extremely hard for a treadmill to keep up because the plane is not relying on its wheels for propulsion. The jet engines would pull the plane forward on the treadmill no matter how fast it is going.
 
jbhtexas

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wolverine68 said:
Obviously a plane is capable of overcoming the friction of its wheels. But a plane is not on a treadmill. Now, if the treadmill is the equivalent of the wheels on a plane (in other words, it won't move unless the plane forces it too) then, yes, the plane would probably be able to take off (the same way that it is possible for a plane to take off with a tail wind). However, if the treadmill had its own power source, if it did not rely upon the plane to gain speed, the forces involved would equal each other out and the plane would not move (relative to the ground below it). If in fact the treadmill could run faster than the plane, then the plan would crash off of the back of the treadmill because (just like the matchbox car) it could not achieve lift..
Click to expand...

The only force that the treadmill belt can impose on the plane is through the friction between the belt and plane tires. As has been explained, and pointed out by equation, and pointed out by some calculations in this thread, the rolling friction force between the tires and a normal treadmill belt is very very small relative to the thrust of the engines.

The treadmill could run 100 times faster than the plane and it wouldn't make any difference, the friction force would still be small. Maybe if you made the treadmill belt out of thick, wet, sticky tar, you might be able to increase the friction force to the point where it could actually counteract the thrust of the engines.
 
tim_redd

tim_redd

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Cars and planes are different. Cars "push" on the ground below them to move forward. Planes "push" the air around them to move forward, regardless of what the ground beneath them is doing.

Is air effected (significantly) by a treadmill?
 
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cmoneyr

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ISU BET said:
explain how the only thing that has to happen is to overcome the friction of the wheels. i am picturing the treadmill as a non motorized hypothetical belt that is somewhat using the planes thrust as its motor to turn the belt around. the faster the planes engines would thrust, the faster the belt would spin, thus negating any forward movement from the plane. but again, this is common sense speaking.
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I've always heard the problem, and I think it's implied in the first post that the belt is motorized. The fact that it can "accelerate to match the speed of the belt" seems to imlpy that.

Go back to what others argue. The wheels spin because there are two opposing forces. The plane is not affected by this. As long as the plane can not move forward, it will not take off.
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I agree, that the wheels spin because of 2 forces, the force of thrust and the force of the treadmill. If a treadmill is going at 50mph and the wheels on it are going at 100mph where do you think this extra speed is going.
 
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cmoneyr

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wolverine68 said:
Obviously a plane is capable of overcoming the friction of its wheels. But a plane is not on a treadmill. Now, if the treadmill is the equivalent of the wheels on a plane (in other words, it won't move unless the plane forces it too) then, yes, the plane would probably be able to take off (the same way that it is possible for a plane to take off with a tail wind). However, if the treadmill had its own power source, if it did not rely upon the plane to gain speed, the forces involved would equal each other out and the plane would not move (relative to the ground below it). If in fact the treadmill could run faster than the plane, then the plan would crash off of the back of the treadmill because (just like the matchbox car) it could not achieve lift..
Click to expand...
The only force that the wheels are going to transmit back to the plane is friction. Since we know that this amount of friction is small then it really doesn't matter how fast the treadmill is going. The plane would take off even if the treadmill was going 2x the speed of the plane, or 3 or 4x even. The wheels would be spinning faster in each situation, but the speed of the plane would be constant over each scenario.
 
CYVADER

CYVADER

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actually the way i read the original post is that the belt will accelerate to match the speed of the plane. it doesn't state whether or not it can match the plane speed due to a motor or if it is the friction of the planes wheels causing it to move.
 
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cmoneyr

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If it ends up moving at a speed equal to the plane then it doesn't really matter how it gets there. The plane will move Xmph, the treadmill will move Xmph is the opposite direction and the wheels will spin at 2X.

There really isn't a better way to state the answer to this problem. It really is very simple if you just think about what's happening here.

A plane is propelled forward by its engines not by it's free-spinning wheels. The plane will move forward and still take off the wheels will just be spinning 2x as fast when that happens.
 
Wesley

Wesley

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Just want to clarify - is this an Airbus with jet engines or a Piper Cub with a prop?
 
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wolverine68

wolverine68

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jbhtexas said:
The only force that the treadmill belt can impose on the plane is through the friction between the belt and plane tires. As has been explained, and pointed out by equation, and pointed out by some calculations in this thread, the rolling friction force between the tires and a normal treadmill belt is very very small relative to the thrust of the engines.

The treadmill could run 100 times faster than the plane and it wouldn't make any difference, the friction force would still be small. Maybe if you made the treadmill belt out of thick, wet, sticky tar, you might be able to increase the friction force to the point where it could actually counteract the thrust of the engines.
Click to expand...

All right, so we all agree that a plane can not take off without wind flowing across its wings. In other words, a plane that is standing still (relative to the ground, not the treadmill) will not take off. What we are arguing is can the thrust of the plane overcome the speed of the treadmill below it in order to create lift. Is that accurate?
 
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cmoneyr

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wolverine68 said:
All right, so we all agree that a plane can not take off without wind flowing across its wings. In other words, a plane that is standing sill (relative to the ground, not the treadmill) will not take off. What we are arguing is, can the thrust of the plane overcome the speed of the treadmill below it in order to create lift. Is that acurate?
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First correct thing I've heard outta you in awhile :wink:

But actually the plane isn't overcoming the speed of the treadmill, all it really has to overcome is the friction in the wheels as they spin faster than normal.
 
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