Brain teaser
 

This turned into a pretty heated debate on another forum I visit. Which didn't really make any sense to me because it has a very simple and logical solution supported by math and physics.
But lets hear what you guys have to say:

A plane is sitting on runway that can move (some sort of giant conveyer belt). 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 opposite direction).

The question is:

Will the plane take off or not? Will it be able to run up and take off?

air speed over the wings is the only thing that should matter

Absolutely, since the wheels aren't driving it. The speed the belt is moving will have no impact on the plan at all except the speed at which the wheels are turning, which again are independant of the actual speed of the plane. the plane will accelerate and presto physics will make the plane take off.

How the hell could that turn into a debate?

just cause the ground is moving doesnt mean the plane isn't. It should still be generating thrust therefore like Phil said air flow on the wings. But what do it know.

treadmill and a rc plane.:gay:

The aircraft will not have velocity. a conventional aircraft will not take flight without velocity as there is no airflow over the lifting surfaces. only a vtol aircraft will be able to generate lift at a standstill (which is really more thrust than lift).

uh... the plane will be standing still.

no airflow around wings = no lift

this is so retarded

I concur.

Yes. :)

What was the arguement for takeoff?


edit:Turns out I'm an idiot! I was right about the retarded part, though heh

Just for the heck of it.

http://www.lerc.nasa.gov/WWW/K-12/airplane/factors.html
read #2.

http://www.lerc.nasa.gov/WWW/K-12/airplane/move.html
More useless factors involved:gay:

Yeah. Read post #6 on this thread.

Ben
AE major

Ben, we all know you're smarter than me. :D

read #2 post btw

Aww! You fixed it before I could point it out!:gay:
:)


Ben
post whorin'

I guess one conceptual issue is this: How long is this conveyor belt? Is it the length of a runway? If so, how does the conveyor belt adjust speed? Does it move 1mph faster for every 1mph the plane moves? Because the wheels are freewheeling, the thrust of the engines would eventually overcome the friction in the wheelbearings and the plane would move forward. The conveyor belt would adjust by speeding up. This would cause the wheels to spin faster, but not necessarily the plane. So the only limiting factor to the plane lifting off (assuming a long enough conveyor-belt runway) is the speed at which the wheels can spin (think toasted wheel bearings and shredded Firestone tires. ;) )

the airplane will take off

airplanes are propelled by thrust and move independently of the wheels. The treadmill will impose more friction upon the wheels and bearing but it will continue to accelerate and eventually take off.

BTW this has been going around the internet for ages.

EDIT: Damn, you guys beat me to it... that's what happens when I start a post, go take a dump and then come back and finish it.

You guys aren't thinking about this correctly.
The wheels don't drive the plane. The thrust of the motor (prop or jet or whatever) moves the plane.

Simply imagine a plane on a giant treadmill runway. When you open the throttle, the plane start to move forward through the air in relation to the earth. As the treadmill moves at the same speed in the opposite direction, all it means is that the wheels will be moving twice as fast. The plane won't know the difference, it'll still go screaming down the runway (now moving twice as fast beneath it) and take off as normal.

Silly civilians.

nobody ever said the plane was running ;)

Damn, it makes sense now. Just needed another Sam to explain it:bigtu:

go run some radios or something and leave this to the REAL pilots.