Spinglo Sponglo! wrote:
Ok, so what's being said is that once you overcome the friction between the wheels and the treadmill the plane does travel along the treadmill?
There's not really any friction overcoming to be done. The wheel will *roll* on the treadmill belt, just as it would roll on a runway.
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Ok thena question, as I'm stuggling to visualise the wheel at the moment
On the runway the wheel is spinning around, on the treadmill is it spinning around twice as fast as it usually would, or is it not spinning at all?
Twice as fast.
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As far as I can imagine it at the moment the engine is pushing the wheel to the right at the top,(clockwise) and the conveyor belt is pushing it to the left at the bottom (also clockwise), so the wheel is going twice as fast as it normally would in "real life".
Correct.
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Now as I understand it, the coeffecient of friction increases exponentially (squared isn't it?) with speed.
This is not applicable. The coefficient involved here is the rolling resistance of the tyre, which is practically a fixed value until high speeds are reached, and then it increases linearly.
Remember, the speed of the wheel in a normal landing is higher than at takeoff, so theoretically doubling the speed isn't earth shattering.
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If this conveyor belt really can match whatever speed the wheel is travelling at, then this friction force is easilly going to match the thrust from the jet.
Picking some numbers, if the plane takes off at 120mph, the experienced speed of the wheel will be 240mph in the silly-treadmill-argument. Even if the force due to the rolling resistance is quadrupled in this case, it is still totally insignificant compared to the force of the engines.
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The Plane goes no where.
Noooo (cries)..