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Discussion Starter #1
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 :D
 

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Non rotating winged aircraft need air speed to fly. That plane would have no airspeed. Or have I missed something:confused:
 

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it cant because the plane isnt moving only the wheels are turning..and they need to be at a certain speed to set off..........if im right what do i win??
 

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Assuming the conveyor belt could match the forward speed that the aircraft's thrust creates, then I would say no.

The aircraft's wheels would be turning but the the aircraft itself would be static. Therefore, no lift.

I must point out that 20 years ago I passed my Physics 'O' Level on the third attempt. lol
 

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No it cant, the plane is traveling at speed but its the ground thats moving not the plane.
As such it is not progressing through the air so no lift could be generated by the passage of air over (or under I dunno how it works) the wings.
 

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Discussion Starter #8
Ok, here goes...

The plane would take off, as normal.

Reason: The wheels act independently of the forward motion of the plane, they're not driven by or connected to the engine. The plane doesn't "drive" the wheels to build up speed, they just rotate as a consequence of the friction between the rubber and tarmac.

The forward thrust of the engines can't be affected by the conveyor, only the wheels are. So basically the plane would "move" forwards even if the wheels were rotating backwards.

It wouldn't matter if the plane was on wheels, or skis, or even on its belly (although friction would increase and more engine thrust would be required to overcome it) - the plane would still move forwards.

It's a bit of a red herring question - the conveyor moves faster proportionate to the speed of the plane - which would simply mean the wheels would go backwards faster and faster, but because the wheels aren't physically connected to the "engine" like a car or bicycle is - it wouldn't make any discernable difference to the speed of the plane.

Hope that makes sense. :)
 

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Durzel said:
Ok, here goes...

The plane would take off, as normal.

Reason: The wheels act independently of the forward motion of the plane, they're not driven by or connected to the engine. The plane doesn't "drive" the wheels to build up speed, they just rotate as a consequence of the friction between the rubber and tarmac.

The forward thrust of the engines can't be affected by the conveyor, only the wheels are. So basically the plane would "move" forwards even if the wheels were rotating backwards.

It wouldn't matter if the plane was on wheels, or skis, or even on its belly (although friction would increase and more engine thrust would be required to overcome it) - the plane would still move forwards.

It's a bit of a red herring question - the conveyor moves faster proportionate to the speed of the plane - which would simply mean the wheels would go backwards faster and faster, but because the wheels aren't physically connected to the "engine" like a car or bicycle is - it wouldn't make any discernable difference to the speed of the plane.

Hope that makes sense. :)
correct :rolleyes:
 

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perfectly sensible. the 'power' i.e the engines are pushing against air. therefore there is no friction between the 'wheels' which are freely spinning and the 'power' , so regardless of the conveyor belt, the wheels would be simply acceleratng faster and faster on the conveyor belt until the plane lifts off.

perfectly sensible ;)
 

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GibraltarR33GTR said:
perfectly sensible. the 'power' i.e the engines are pushing against air. therefore there is no friction between the 'wheels' which are freely spinning and the 'power' , so regardless of the conveyor belt, the wheels would be simply acceleratng faster and faster on the conveyor belt until the plane lifts off.

perfectly sensible ;)

Ahhhhhhhh!!! If you had taught me physics, I would have passed first time.

Durzel, you're a crap teacher. :D
 

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R32 Combat said:
Non rotating winged aircraft need air speed to fly. That plane would have no airspeed. Or have I missed something:confused:

Don't think you have missed anything. The plane will not take off. If the belt matched the speed of the plane, then that means its stationary in relation to the air around it. So no air passing the wings = no lift. The wheels don't even need to be considered.
 

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weka said:
Don't think you have missed anything. The plane will not take off. If the belt matched the speed of the plane, then that means its stationary in relation to the air around it. So no air passing the wings = no lift. The wheels don't even need to be considered.

That is what I reckoned....and now I am totally bamboozled. lol
 

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Discussion Starter #20
The easiest way to think of it is as follows:

1. The wheels do not make the plane move. They just spin.
2. The conveyor belt cannot provide a significant amount of force to the plane itself, as the wheels are free to rotate.
3. The engines exert a lot of force on the body of the plane and push it forward.
4. There is no force whatsoever, aside from the minimal friction in the wheels, pushing backward on the plane.
The wheels are a bit of a red herring really. If it was a car instead of a plane on the conveyor belt then the car would not move, because a car moves BY turning the wheels, and the wheels are driven by the engine. A plane (either propeller or jet-engined) moves because of air being forced backwards during thrust, the wheels are just there to reduce friction - nothing more.

It would not matter if the wheels were rotating backwards, forwards or sideways.
 
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