Quote:
Originally Posted by KenWittlief
its really a trick question. If you think the airplane will stay in one place, because the treadmill is 'matching its speed' - thats impossble.
If the plane is staying in one place then its speed is zero. If the planes speed is zero then the treadmill speed is zero. So whats stopping the plane from taking off? where does the force come from?
The only way the treadmill CAN move is if the plane is moving - and if the plane IS moving the treadmill is not holding it in one place.
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This argument reminds me of that trouble-making ancient Greek philosopher, Zeno. To paraphrase him tremendously, he argued that motion is impossible.
Take the example (as he did) of an arrow shot from a bow. It is understood that the arrow exists, and takes up space, and at every infinitessimal instant, has a known position. Since positions are absolute and immobile (as measured from your frame of reference, i.e. the earth's rotation), the arrow does not move because at any given freeze-frame moment it is in a given position & orientation and therefore it is still.
We all know this is not true, otherwise Robin Hood would have been out of a job. But, as Zeno endeavored to prove, it does show the fallability of human logic. There are many more instances that recall this notion (Heraclitus saying one can never step in the same river twice, and the completely ridiculous "if a tree falls...." nonargument) that show that logic can be used to prove (or disprove) nearly anything.
To discuss the notion of a giant fan producing lift (or "suck") to the plane, this would be a colossal mistake. As soon as the plane leaves the wind chute provided by the fan, it would enter the (relatively) still airmass and fall back down, either tilting back each time and eventually reaching a stall or resulting in a nosedive.