That's awesome, UT!

Yes it does:

It matches the forward speed, cancelling all forward motion. UT's animation repeatedly says "as the plane moves forward" but that is not the scope of what we are discussing. We are discussing a stationary plane.

Fuck the wheels, fuck the treadmill, fuck the thrust. Lift is produced by air moving across the wings. Moving.

I found it after googling for the problem... turns out it was fought over by folks on a physics board, so I feel a little less foolish...

Flint. The wheels don't matter as far as forward motion is concerned. As the graphic that UT says, the wheels will just spin twice as fast. It doesn't matter how fast the treadmill is going backward, because the plane's pushing against the air, not the ground.

:corn:

(Not being sarcastic...I find this debate fascinating)

Fuck how fast the wheels are spinning. No forward motion = no lift.

The only item of discussion here is how you read the question. Stationary planes (commercial jetliners) do not jump into the air. Ever.

If I understand you, the above part of the problem set means "no forward motion" to you. I don't think it does. It would for a car. It doesn't for a plane.

It doesn't mean that to me. I would say there is most certainly forward motion in the way I described it. The wheels are free spinning despite the treadmill.

No, this part does: There aren't two different reasons for the wheels to spin. They only ever spun because the plane was trying to move forward, and the treadmill matches the forward speed, cancelling it. If the plane thrusts harder, the treadmill continues to cancel it's motion. There is no tip-over point, here. The treadmill prevents the plane from moving. The plane cannot take off from a stationary position.

Get a motorized treadmill and a bicycle. Hold the bicycle in place and turn the treadmill up as high as it will go. Are you having to fight very much to keep the bike stationary? No -- the friction between the bike frame and wheels is very low. Now, push the bike forward. Is it taking much effort? Not at all.

It doesn't matter how "hard" it is. In this scenario, you can't do that.

The plane will move forward, no matter how fast the treadmill is going. The treadmill can't cancel the forward motion of the plane, because the plane's speed is not determined by the wheels. If you hold a hotwheel car in your hand, and put it on a treadmill, you can move it forward no matter how fast the treadmill is going. Likewise, the jet engine will move the plane forward no matter what the treadmill and wheels are doing.

Now, if it were in a wind tunnel, and air was blown to cancel the jet engines, that would be a different story.

You're right: if you ignore the question you can get whatever answer you want.

Nothing in the question says the plane is stationary. Just that the treadmill moves. But the treadmill can not stop the plane! The assumption that the plane is made stationary by the treadmill is something that you are bringing in, and is the trick part of this trick question.