Interesting conundrum.

[KrisR]

Read the question and really think about it before you answer.

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 opposite direction).

The question is:

Will the plane take off or not?

[Newbomb Turk]

You made me think. You suck.

[MetallicPony]

yeah a few other forums i lurk have that debate going....bunch of 20+ page threads debating it.

here we go.... :hah:

[worduphomefry]

yes

[KrisR]

yeah a few other forums i lurk have that debate going....bunch of 20+ page threads debating it.

here we go.... :hah:

[StangerJon]

man that took a while to read and understand what was going on.

I say no. because while the planes engines are going, it is still on the conveyor which is making it so the wings are not moving through space making them not generate any lift.


it would simply be a very loud noice machine.

[worduphomefry]

but the planes motors aren't on drive wheels so those are there just spinning so the plane can move cause the it's using the air to move which isn't effected by the "belt"

[MetallicPony]

took this from fordpower.net

This is not a logic problem. This is a simple physics problem, once you understand the forces at work here (pun definately intended).

First of all, we need to conisider the problem... lets assume we're talking about a Jet, though a plane with prop would yield the same results:

1. Jet sits on a conveyer belt
2. The conveyer belt will match the jet wheel speed at all times
3. Will it fly?

Lets look at item #2... I drew a diagram.

Friction... friction occurs when there is slipping between two points. Lets look at the point where the wheel touches the conveyer. The point where the wheel touches the conveyer and the conveyer both have the same velocity and in the same direction. This means that there is no slipping between them, and thus, there are no friction forces that eminate from the wheel/conveyer interation.



So, this illustrates that because the conveyer matches the speed of the plane's wheels, there is no friction force eminating from the wheel/conveyer interaction.

This right here is the key to understanding this solution. Re-read if necessary.





If you've managed to understand the friction conclusion from above... we move on.

So now we look at what forces are left:
1. Thrust force from the jet engines, T
2. Gravity force (mass*g), N

When force T is applied to the plane, it will accelerate forward at a rate of accel = T/mass.

Now, here is where the understanding of friction forces from above come into play...

So, yes... when the plane accelerates forward, the conveyer accelerates also to match the wheel speed. BUT, since the wheel/conveyer interaction yields NO FORCES, there is nothing to counteract the "acceleration = T/mass" of the plane.

So, if the only acceleration is due to thrust, T, then the plane will move forward and take off.



We can ignore the Normal force due to gravity because that's beyond the scope of the question.

So, in conclusion, the plane will take off.

[worduphomefry]

that answer is to complicated, i like mine better

[The Russinator]

but the planes motors aren't on drive wheels so those are there just spinning so the plane can move cause the it's using the air to move which isn't effected by the "belt"

[RayK]

Read the question and really think about it before you answer.

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 opposite direction).

The question is:

Will the plane take off or not?

no

[MetallicPony]

that answer is to complicated, i like mine better

you lose

[worduphomefry]

jargin

i don't even know what that funny looking E means. i must be wicked smart

[StangerJon]

ohh snap. appearently I still didnt think hard enough.

this question owned me.

[Xtort]

I think I remember that question from ninth grade..