Quote Originally Posted by tony
Saw this on Supraforums and it was a pretty interesting read.

A plane (747 passenger jet) is sitting on a runway that can move (some sort of band conveyor). The plane moves in one direction, while the conveyor moves in the opposite direction. This conveyor has a control system that tracks the planes speed and tunes the speed of the conveyor to be exactly the same (but in the opposite direction).

The question is:

Will the plane (747 passenger jet) take off or not?
I would say that it wont take off. If this was in a closed room, where there was no opposite air flow moving under the wings then ti wont take off. Say even if you have a conveyor moving in the opposite direction of the plane, then the plane starts up thrust to move the plane forward to match the speed of the conveyor. But the way the question is worded, you said that the thurst and the conveyor would be moving at the same speed. Well for what you guys are saying that the wheels will beat the drag, then the thrust would have to have a constant gain of velocity, but the question is that they match the speed. So this question could almost be considered impossible becuase if you had a conveyor that could completely match the planes thrust, then you would have a machine that was 100% efficent. But in this situation if it could happen then they conveyor would match the speed of the belt for everybit of its gain on the belt the belt would jsut speed up.

I mean i could be wrong but from what i understand even if the wheels beat the drag, the belt would jsut speed up more, to coincide with the planes thrust. To me its the same way as saying if you had someone pushing an object with 50N of force to the north and then had someone pushing with 50N of force on the same object to the south, they woudl jsut cancel out!