The Airplane-Treadmill Conundrum

[friskyRadio] Intensified - 01 December 2008 - Jody Wisternoff

The Airplane-Treadmill Conundrum

December 13th, 2006 Random Post of Wisdom | Digg This | ##

This riddle has been making the rounds on the Internet lately and is a classic brain-tease. Consider this:

“Imagine a plane is sitting on a massive conveyor belt, as wide and as long as a runway. The convener belt is designed to exactly match the speed of the wheels, moving in the opposite direction. Can the plane take off?”

Here’s my answer:

Of course it will. A plane’s power and torque comes not from its wheels, like in a car, but from its engines. So if the plane’s engines are all fired up, they would propel the plane forward by sucking the air into them and producing thrust. Enough thrust would cause the airplane to start moving forward, even if the wheels on the conveyor belt are moving madly. What causes the plane to take to the air is lift. If the plane is moving fast enough, the air passing along its wings will produce lift - which, if enough, will cause the plane to take off.

Anyone disagree or still not convinced?

6 Comments

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1 Sarah Dec 15th, 2006 at 12:01 pm

That would save so much space at airports, lol.
2 Ingo Vogelmann Nov 2nd, 2007 at 5:07 am

It won’t take off, mate. Because it’s not moving forward. It’s standing at one point and there is no air from the front that floats under the wings to lift the plane up. The thrust is ONLY responsible for the forward movement NOT for the lift. There must be lots of air pressure (like with birds and their wings) underneath the wings that will let the aircraft leave the ground.

The belt takes away the forward movement - which is responsible for that air pressure - completely.

Same with a huge propeller and a sailing boat. The boat won’t move one inch.
3 Ingo Vogelmann Nov 2nd, 2007 at 5:08 am

Addition: A propeller ON the sailing boat.
4 frisky? Nov 2nd, 2007 at 9:24 pm

Ingo: You and I are saying the same thing yet you say it wont take off. It is moving forward! The power comes from the thrust of the engines, NOT the torque in the wheels. Thus the thrust will start to power the plane forward - causing wind to flow between the wings - which causes lift. ENOUGH speed = enough lift = plane takes off.

By the way I have a minor in Aerospace Engineering. I started my college as an Aerospace Engineer before changing my major to Computer Science. I also have a Private Pilots license, although I haven’t flown since 2000.

f.

1 | friskyGeek Pingback on Nov 1st, 2007 at 6:48 pm
2 Airplane on a Treadmill :: Mystery SOLVED | friskyGeek Pingback on Jan 31st, 2008 at 5:58 pm

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