Can A Plane Take Off On A Treadmill?
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From: Longmont, CO
You can actually take advantage of the fact that static friction is higher than dynamic friction in order to do a complete revolution. 
It'll take a while, though, and you'll look awfully silly doing it. 
(Also, did you know that there's actually no difference between the two? Sometimes called stiction and friction, the supposedly higher stiction is actually a result of surface irregularities - when two objects are sliding over eachother, the tend to not have as full a contact with eachother as when they're at rest.)
It'll take a while, though, and you'll look awfully silly doing it. (Also, did you know that there's actually no difference between the two? Sometimes called stiction and friction, the supposedly higher stiction is actually a result of surface irregularities - when two objects are sliding over eachother, the tend to not have as full a contact with eachother as when they're at rest.)
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From: Tampa Florida
Originally Posted by Vi37573r,Feb 13 2008, 05:16 PM
If you understand that forward momentum will allow the plane to gain altitude then you're almost there.
The biggest task to tackle is realizing that the treadmill has no effect on the plane.
Imagine this, a car is sitting in a large pool of oil. No matter how hard you step on the gas the car will not move due to the frictionless surface. Now if you apply an external force, (push the car with a stick or something) The car will move in that direction regardless of the speed of the wheels.
The plane and the treadmill are similar in that fashion. Assuming that the friction in the wheels are negligible, the moving treadmill will just freely spin the wheels.
It's hard to find a perfect real world example due to the fact that frictionless wheels do not exist but if you have a skateboard or roller blades you can try it.
Stand on the skateboard on the treadmill when it's stopped. Using your hands on the handle bars, move forward(External force). Try to remember how much force you used. Now turn on the treadmill while holding the handlebar (to compensate for the friction in the wheels). Try to move yourself forward like earlier. You should notice you're using the same amount of force to move the same speed. To further test it, turn up the speed some more and do it again.
The speed that the wheels are traveling is the speed of the treadmill going backwards + the speed of your forward movement, BUT the speed relative to ground is just your forward movement.
This works because the wheels are free spinning, like the plane. The wheels will spin at a speed to match the treadmill, with no more force than to cancel out the force of friction. Therefore, since the plane has free spinning wheels, the treadmill will just speed up the wheels.
The external force of the engines/propellers will make the plane move forward (like your arms from the skateboard experiment).
The wheels of the plane, like the skateboard, will be moving at the speed of the treadmill + the speed of the forward movement, but relative to ground only the speed of the forward movement.
Then the plane will move forward, and this will help create the lift to get it airborne.
The biggest task to tackle is realizing that the treadmill has no effect on the plane.
Imagine this, a car is sitting in a large pool of oil. No matter how hard you step on the gas the car will not move due to the frictionless surface. Now if you apply an external force, (push the car with a stick or something) The car will move in that direction regardless of the speed of the wheels.
The plane and the treadmill are similar in that fashion. Assuming that the friction in the wheels are negligible, the moving treadmill will just freely spin the wheels.
It's hard to find a perfect real world example due to the fact that frictionless wheels do not exist but if you have a skateboard or roller blades you can try it.
Stand on the skateboard on the treadmill when it's stopped. Using your hands on the handle bars, move forward(External force). Try to remember how much force you used. Now turn on the treadmill while holding the handlebar (to compensate for the friction in the wheels). Try to move yourself forward like earlier. You should notice you're using the same amount of force to move the same speed. To further test it, turn up the speed some more and do it again.
The speed that the wheels are traveling is the speed of the treadmill going backwards + the speed of your forward movement, BUT the speed relative to ground is just your forward movement.
This works because the wheels are free spinning, like the plane. The wheels will spin at a speed to match the treadmill, with no more force than to cancel out the force of friction. Therefore, since the plane has free spinning wheels, the treadmill will just speed up the wheels.
The external force of the engines/propellers will make the plane move forward (like your arms from the skateboard experiment).
The wheels of the plane, like the skateboard, will be moving at the speed of the treadmill + the speed of the forward movement, but relative to ground only the speed of the forward movement.
Then the plane will move forward, and this will help create the lift to get it airborne.
New equation:
So with that same logic with the treadmill going in reverse (meaning the same direction as fwd momentum dictates)and me being on (skates/or skate board ) as in your scenario, it should net the same results right/ Meaning you will go the same speed relitive to the ground and the amount of force exerted....correct?
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Originally Posted by duboseq,Feb 13 2008, 11:05 PM
I think I get it now! Thank you Jesus!!! I am going to try that on the treadmill, hopefully I dont bust my tail!
New equation:
So with that same logic with the treadmill going in reverse (meaning the same direction as fwd momentum dictates)and me being on (skates/or skate board ) as in your scenario, it should net the same results right/ Meaning you will go the same speed relitive to the ground and the amount of force exerted....correct?
New equation:
So with that same logic with the treadmill going in reverse (meaning the same direction as fwd momentum dictates)and me being on (skates/or skate board ) as in your scenario, it should net the same results right/ Meaning you will go the same speed relitive to the ground and the amount of force exerted....correct?
If I understand your question, you are correct. The direction does not matter.
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Originally Posted by Elistan,Feb 13 2008, 10:49 AM
Okay, it sounds like what you're saying is that a plane's engines can be feathered so low that a plane on a backwards moving treadmill can be held stationary. That is true. There's enough rolling resistance in a plane's wheels that some small force will want to push it backwards, and the engine can counter that with a tiny little bit of thrust.
I hope you realize though, that does NOT mean that the treadmill has any ability WHATSOEVER to prevent a plane from taking off, because the amount of rolling resistance is the same whether the treadmill is moving at 10mph or 10,000. Meaning, if the plane can overcome the resistance of a stationary runway, it can overcome the resistance of a runway moving backwards at any speed.
In our above example of a stationary plane on a moving treadmill, if you increase the speed of the treadmill from 10mph to 500mph, the plane will continue to remain stationary without any change to the engines.
I hope you realize though, that does NOT mean that the treadmill has any ability WHATSOEVER to prevent a plane from taking off, because the amount of rolling resistance is the same whether the treadmill is moving at 10mph or 10,000. Meaning, if the plane can overcome the resistance of a stationary runway, it can overcome the resistance of a runway moving backwards at any speed.
In our above example of a stationary plane on a moving treadmill, if you increase the speed of the treadmill from 10mph to 500mph, the plane will continue to remain stationary without any change to the engines.
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From: VA Beach via South Jersey
Originally Posted by 714s2k,Feb 13 2008, 07:06 PM
Who says theres not a big ass fan blowing air at it 
I dont understand whats hard to understand here. Maybe its cause i work on Navy jets(tomcats and now super hornets). The principal is simple. Jet on runway pushes the throttles forward to accelerate. For flight to happen the jet has to overcome the drag that the aircraft exerts on the atmosphere. In doing so it pushes air over the airfoil(wing) creating 2 pressure systems basically. on top the wing has less pressure and the bottom the wing has more pressure. The reason behind that is the shape of the airfoil and how the air moves around it. This is how lift is generated and flight is achieved. now the same jet on a treadmill will just spin the wheels and in a frictionless environment the jet will move nowhere. Now being far from a perfect world the jet will move backwards due to the friction exerted from the weight of the aircraft on the wheels.
Am I making any sense? Am I crazy?
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Originally Posted by Elistan,Feb 13 2008, 10:01 PM
Okay, so you do believe that the plane will be able to take off no matter what the treadmill does?