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

[womble]

Ok this is a conversation I had from a colleague that has an IQ as high as a very high thing and some say he is a tame alien with a brain the size of a planet.


[09:01] Mike (Skymarket): "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?"

[09:06] hairytart: The plane will take off when its air speed reaches a certain amount. What isn't made clear here is whether the plane is moving relative to the conveyer (therefore not moving relative to the planet and the atmosphere) or whether the plane is moving but because of the actions of the conveyer its wheels are spinning twice as fast as they should be.

[09:12] Mike (Skymarket): i would have said yes it will take off as the wheels are just free wheeling (little or no friction) and that the wheels are not driven. The thrust is provided by the jet engines so as long as they have more thrust than friction the plane will always move forward. The wheels would only free wheel twice as fast as if they were on the fixed flooring.

[09:13] hairytart: yes I agree
The unclear bit is whether that was what the question actually meant
Itís a badly worded question really

If the plane was wheel driven (clearly a daft idea) then the question might have had more validity, though the plane would tend to slow down the moment it left the tarmac!

And before you ask yes he is hairy and his surname is Tart!