Can the Plane Take Off ?

[S2 Ant]

right this is becoming quite the hot topic on a few other forums,

A plane is standing on a runway that can move (some sort of 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 the opposite direction).

Can the plane take off?

Discuss.......



Well can it ?

[S2-racer]

no, as there is no air flow over the wings to generate the lift required for take off.
simple physics really, lol

but then i could be wrong

[Ross]

But, if the plane is gonna just sit still on the conveyor belt, where's all the energy from the 1,000's of LBS of thrust going? Remeber the plane doesn't accelerate due to power transmitted to the ground

I'm voting for the "yes, if the wheels don't drop off first" option.

[RustyNut]

Yes it can. Doesn't matter as the Jet will move as normal only the wheels will be moving quicker than usual. There would be slightly more resistance but not much as it's not being propelled by the wheels?

[newsh]

I agree with S2-Racer

[newsh]

The plane will only leave the ground if the wings can generate lift, its air speed not ground speed that makes it fly.

[Alistair C]

'Course it can take off.
Wheel speed is irrelevant.

[Corey]

The wings are stationary, period. Without any air flow over the wings they cannot generate lift.
Don't matter a monkey's nut what the wheels are doing.

[S2 Ant]

its actually a v poorly worded puzzle really i think, because it will depend on how much influence the thrust can have over the wheels trying to move on the ground as the aircraft would accelerate gradually the only way it couldnt would be for the conveyor to exceed the speed the wheels are moving at to counteract the thrust. so the plane would eventually take off i believe.
Also backed up by because the plane is propelled by engines generating thrust, not power to the wheels.

[Corey]

because it will depend on how much influence the thrust can have over the wheels trying to move on the ground as the aircraft would accelerate gradually the only way it couldnt would be for the conveyor to exceed the speed the wheels are moving at to counteract the thrust. so the plane would eventually take off i believe.

Contradicting yourself there, you said that the conveyour tracks the planes speed so that it remains stationary.

[marty]

I agree if there is no air movment over the wings no lift. But if the planes engines are running no matter how fast the conveyer runs it will not stop the plane from moving fowards just increas wheel rpm so it would fly.

[S2 Ant]

thats why i said its poorly worded, because if for instance you had roller skates on and were stood on a mechanical tread mill and turned it on, there is a jerk in the direction of the force applied, ie backwards, but once the acceleration has stopped you can steady yourself and remain stationary, so if the plane was to fire its engines up there would be an equal response in the direction the plane is wanting to go, ie forwards, if the plane kept on trying to accelerate it would go forwards.

It is v badly worded tho i think so i think there are arguments either way really.

[newsh]

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 the opposite direction).

The plane is not moving relative to the air, obviously it cannot take off..

[S2 Ant]

but in order to overcome that initial force, surely it would have to initially go faster than the plane wanted to otherwise force is greater in one direction than the other.

[newsh]

Look at it another way, a plane flying at 300mph encounters a 300mph headwind, what is its speed in relation to the ground?