Mythbusters, Plane on a treadmill..

[Seadogrun]

I'm really dissapointed at myself for getting into this discussion, but here goes.

Coopervane rewrote the original question in an incorrect manner. The original internet sensation question never states that the airplane remains in the same relative position. It merely states that the treadmill spins in reverse at the same speed as the airplane's wheels. Despite this, people have still been arguing that the plane can't take off for a couple of years now. The problem really isn't Coopervane's question (although it was rewritten incorrectly), the problem is that people don't understand basic physics.

If the airplane wheels match the speed of the treadmill's speed would there be forward motion of the airplane?

For there to be forward movement of the airplane the airplane's wheels would need to be at a higher speed than that of the treadmill.

The devil is in the details. It really depends on the origional question.

 

[XPOO]

Perhaps the Mythbusters could have used to Harrier Jet to demonstrate this treadmill theory?!

 

[PCL_128]

If the airplane wheels match the speed of the treadmill's speed would there be forward motion of the airplane?

For there to be forward movement of the airplane the airplane's wheels would need to be at a higher speed than that of the treadmill.

The treadmill attempts to match the speed of the wheels, but it physically can't, because the airplane continues to accelerate until it takes off. The treadmill is incapable of holding the airplane back, because the prop provides the forward motion, not the wheels.

 

[Crossky]

I did a little test with my daughter's toy car on our treadmill. I set it at 1 mph, 5, mph, 10 mph, and the max speed, while holding the car, preventing it from rolling backwards.

I felt the drag on the car produced by the sum of drag force of the treadmill against the wheels plus the friction force of the axles spinning in the plastic mounts. This total drag felt the same (to my trained fingers!) with each speed I set the treadmill to. It was the same constant drag at 5 mph as it was at the max speed the treadmill would go (about 15+). Thus, when applied to the aircraft situtation the plane needs to produce just enough thrust to over come the total drag force of the treadmill/wheels and it will start accelerating. A matter of fact, the treadmill could move faster than the plane, and the plane will still accelerate if it's producing enough thrust to overcome the total constant drag previously mentioned.

I'm too lazy and don't have a fish scale (or a hanging science force scale), but one could use one of these scales to videotape and youtube post the constant drag produced on a toy car held still on a treadmill at different speeds.

 

[XPOO]

I did a little test with my daughter's toy car on our treadmill. I set it at 1 mph, 5, mph, 10 mph, and the max speed, while holding the car, preventing it from rolling backwards.

I felt the drag on the car produced by the sum of drag force of the treadmill against the wheels plus the friction force of the axles spinning in the plastic mounts. This total drag felt the same (to my trained fingers!) with each speed I set the treadmill to. It was the same constant drag at 5 mph as it was at the max speed the treadmill would go (about 15+). Thus, when applied to the aircraft situtation the plane needs to produce just enough thrust to over come the total drag force of the treadmill/wheels and it will start accelerating. A matter of fact, the treadmill could move faster than the plane, and the plane will still accelerate if it's producing enough thrust to overcome the total constant drag previously mentioned.

I'm too lazy and don't have a fish scale (or a hanging science force scale), but one could use one of these scales to videotape and youtube post the constant drag produced on a toy car held still on a treadmill at different speeds.

The only draw back is reaching that point before the aircraft wheels reach their maximum velocity. After that, they fail to overcome the drag force caused by the friction and the aircraft actually moves backwards, or the wheels fall off altogether, or the treadmill breaks down into a fiery molten rubber goo. But still, its all hypothetical.

 

[No.W.]

This is fun reading.

 

[CFI2766]

NO relative motion, NO flight.

It doesn't matter how the question is asked, this is what is really being tested.

Yes, I know the tires are not providing motion.

 

[Max Q]

Why is there no relative motion?

-Brett

 

[COOPERVANE]

Shoot this thread in the head twice please!!