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

[camsmith]

Why, did you put the parking brake on?

As mentioned earlier, thrust is provided by either a propeller or a jet engine. The amount of force (and therefore acceleration) provided is purely dependant upon the surrounding air, minus any friction from both the air itself and the surface on which the plane rests before it is flying.

The only reasons a plane has wheels and tyres are;
1 - to reduce the friction provided by the ground when taxiing/taking off
and
2 - to assist in controlled braking when landing.

The theory is completely different to a car, where the engine applies a rotational force to the wheels, which translates to a translational (forward) force where the tyres contact the ground. In a plane, the force is provided by the surrounding air, not the ground underneath the plane.

Therefore, the plane will take off and quaker's stick will go unused.

This post has been edited by camsmith: Feb 24 2006, 02:11 PM