Physics Question: Will the plane take off? (27 page debate on elisetalk)

A plane is standing on a runway that can move like a giant conveyor belt. The plane applys full forward power and attempts to take off. This conveyer has a control system that tracks the plane’s wheel speed and tunes the speed of the conveyer to be exactly the same but in the opposite direction, similar to a treadmill.

The question is:

Will the plane take off or not?

personally, i think it is a dumb question and painfully apparent, but of the 125 people that voted, only 67 of them said yes… :ham:

what will happen, in my opinion, is the plane will accelerate until it reaches lift speed. It will begon moving away from a stationary point (not on the treadmill) at normal speed.

What i can’t decide is whether or not the wheels will merely spin at twice the correlating groundspeed, or whether they will accelerate towards infiniti… if i felt like writing this on paper, i suspect that velocity would approach infinity.


I dunno… yes the wheels are spinning but the plane is not moving. I don’t know very much about airplanes but I say that it doesn’t take off.

Also… if the conveyor belt is matching the wheels for speed the wheels won’t spin twice as fast. They should spin at normal speed. Hence is not moving anywhere on the conveyor belt.

wheels are not providing any thrust, their only purpose is to keep the plane off the ground while engines provide forward motion.

If the plane was driven by its wheels then no, it would not take off nor would it go anywhere. Imagine you were wearing rollerskates on a treadmill with someone behind you pushing on your back to keep you from falling off. Now if that person gives you a huge push (like the engines on an airplane) you will move forward with no problems.

Idk im probably 100% wrong, thats just how I imagine it.

edit- I didnt read that last part of your question very well. :ham:

exactly. and no, planes are not driven by their wheels…

well the plane is going to take off for sure. Like you said, thrust is self provided by the airplane. The ground isn’t helping the plane take off, its the speed and thrust from the plane itself. I’m not sure about the wheels…hmmm…

Ah, see i didn’t know that about planes. Then with that said I would definately think that it could take off. That would be an awesome way to build airports. Save so much space.

There was a huge discussion on the Barf about this. The question is misleading which causes people to have different conceptions of the problem.

What I initially thought was that the plane will not take off because, I was thinking it had to break the friction point between the wheel and the treadmill, depending what that friction point was was debatable. At that point it will not move forward. And I thought this up and down till I realized what other people were thinking.

The answer is that it will move forward and thus take off when it reaches lift speed because, once friction is broke, the wheels are independent of the engine (you can’t look at it like a car on a dyno). The wheels will be moving twice as fast. There’s a simple way to test this.

If you have a treadmill at home. Turn the treadmill on and reverse it’s incline so the front of the treadmill is facing down and the back of the treadmill is up. Then put a matchbox car on the treadmill and see where it goes. Although the treadmill is going one way, the matchbox car will move in the opposite direction because the wheels are independent of it’s engine (gravity).

Thats the way I figured it out.

Paging Mr. Wizard!

no, you still need just as much room, the plane still has to attain the same forward velocity, thus needs to travel the same distance, with respect to a stationary point, independant of the treadmill…

I dont think it would save any space. The conveyor is actually pretty irrelevant to whether or not it will take off. No matter what, its going to need to move in order to take off.

edit- goddamnit newman.

What about the friction that would be present in the bearings of the wheels? If that was not a factor, I would imagine that the wheel speed would continue towards infinity. But factor in friction, the wheels will reach a terminal rotational speed and either stop accelerating or probably burst into flames.

The basic question is easy, and anywho who said ‘yes, the plane will take off’’ needs to revist high school physics. However, the supporting factors offer some interesting avenues of thinking.

but the plane would move. the wheels do not accelerate the plane. if you put a car on the conveyor you would be able to drive in one spot. The plane operates on thrust from a jet engine. the conveyor would have no effect since the air that is actually moving the plane would still be the same.

this went quick…

How would it not take off?

Picture your feet being the wheels of a plane. If the plane was driven by the wheels then it would be exactly like running on a treadmill. The faster your feet moved, the fastr the conveyor would move and you would sit stationary. Seeing how planes are NOT driven by their wheels it would be like what I said with the rollerskates and someone behind you pushing you forward. The plane will take off.

I’d to say no…there is NO LIFT

The THRUST force makes the aircraft speed up along the runway.
Why doesn’t it take off?

The WEIGHT force is bigger than the LIFT force.

Now, IF the LIFT force is bigger than the WEIGHT force.
The forces are unbalanced, and the aircraft starts to rise.

Lol, just read UBRF, it was debated and proven over there. It takes off…

Ahhh, welcome to the NYSpeed’s Debate of the UBRF Debate thread.

Of all people, JoesTypesS posted this on UBRF.

The UBRF thread was actually kind of good, suprisingly.

Annndddd, Yes, the plane will still take off.

the plane will definitely take off… what planet are you from?

the wheels would not approach infinity, however. If forward velocity reached a constant, and the runway was infinitely long, as time tended toward infinity, wheelspeed may, but since you cannot have instant acceleration, and time is limited to takeoff, the wheels could not approach infinity.

yes thrust is independant of wheen speed…

This looks like a job for Mythbusters!

EDIT I take back what I said. It will definately not take off. The plane needs lift which will not occur when the plane cannot move. Conveyor belt matches the speed no matter what.