Brainteaser Options

[james]

Here's a question for you:

"A plane is standing on a runway that can move (some sort of band conveyer). The plane moves in one direction, while the conveyer moves in the opposite direction. This conveyer has a control system that tracks the plane speed and tunes the speed of the conveyer to be exactly the same (but in the opposite direction). Can the plane take off?"

A couple of links discussing it (and some funny rationalizations for peoples incorrect assumptions):
www.kottke.org/06/02/plane-conveyor-belt
www.straightdope.com/columns/060203.html

[james]

Well yeah I understand what you are saying but as the question is about a plane which by definition has enough thrust potential (fnarf) to reach takeoff velocity, so as you said in the last paragraph -

If this was the case then the plane wouldnt take off even if it was on a normal runway

so I'm not sure what you are driving at? Unless you were just commenting on a hypothetical situation outside of the scope of the original question in which case yes you are absolutely right.

Rory - regarding

conveyor belt counteracting the forward motion provided by the thrust of the jets

- by the logic of what you have said the conveyor would need to be applying thousands of pounds of force in the oposite direction to the direction of the engines - but as friction in the frewheeling wheels is almost negligable, increased speed on the conveyor does not translate to force against the plane.