Jump to content


Welcome to BrainDen.com - Brain Teasers Forum

Welcome to BrainDen.com - Brain Teasers Forum. Like most online communities you must register to post in our community, but don't worry this is a simple free process. To be a part of BrainDen Forums you may create a new account or sign in if you already have an account.
As a member you could start new topics, reply to others, subscribe to topics/forums to get automatic updates, get your own profile and make new friends.

Of course, you can also enjoy our collection of amazing optical illusions and cool math games.

If you like our site, you may support us by simply clicking Google "+1" or Facebook "Like" buttons at the top.
If you have a website, we would appreciate a little link to BrainDen.

Thanks and enjoy the Den :-)
Guest Message by DevFuse
 

Photo
- - - - -

Does the plane take off?


  • Please log in to reply
1 reply to this topic

#1 Martini

Martini

    Senior Member

  • Members
  • PipPipPipPip
  • 770 posts

Posted 27 August 2007 - 04:29 AM

A jet plane is on a long treadmill and the pilot attempts to take off in the normal fashion. The treadmill is designed to track the speed of the plane and go that exact speed in the opposite direction. Does the plane take off?

Now take the same situation and replace the jet plane with a propeller plane. Does the plane take off?
  • -1

#2 bonanova

bonanova

    bonanova

  • Moderator
  • PipPipPipPip
  • 5891 posts
  • Gender:Male
  • Location:New York

Posted 27 August 2007 - 06:03 AM

Answer for a jet:
Yes.

Answer for a propeller plane:
Yes.
Reasoning:
An airplane takes off when its wings generate a lift force greater than its weight. Lift force is determined by air speed. A backward-running treadmill will not impede the plane's forward motion, nor limit its air speed, only make its wheels spin twice as fast!

But what if an airplane's engine drove its wheels? Then the answer would be No. It could not achieve forward motion nor generate lift.

That would be an interesting kind of airplane - after it took off it would become a glider!
  • 0
The greatest challenge to any thinker is stating the problem in a way that will allow a solution.
- Bertrand Russell




0 user(s) are reading this topic

0 members, 0 guests, 0 anonymous users