Airplane on a Conveyor conundrum

[dieselboy]

How can something that is moving, be not moving?

exactly.

if you drive away from tescos in a straight line, you move away from tescos correct?
so, if you are travelling at 20mph away from tescos, then tescos is travelling 20mph away from you correct?

where is GWH ? i think he will know exactly how to explain how what i am saying is true

[nero279]

We can only assume both are stationary at the start, as the conveyor matches the planes speed, not the other way round. It may even have stated that both are stationary at the start, i can't be arsed to go back and look

You can't measure the conveyor belt speed relative to the conveyor belt, so why measure the planes speed relative to the conveyor belt?

The only logical way is to measure all the speeds relative to a fixed point.

Keeping all the above in mind we can disregard any need for the engines thrust to overcome any rearward motion of the plane. Even if you can't agree with the logical argument for this then agree with the illogical one that if the plane did begin to move backwards then the conveyor belt would oppose it by beginning to move forwards

Given that we are told the air is still, aren't groundspeed and airspeed the same? At what point do they become different?

[dieselboy]

We can only assume both are stationary at the start, as the conveyor matches the planes speed, not the other way round. It may even have stated that both are stationary at the start, i can't be arsed to go back and look

You can't measure the conveyor belt speed relative to the conveyor belt, so why measure the planes speed relative to the conveyor belt?

The only logical way is to measure all the speeds relative to a fixed point.

Keeping all the above in mind we can disregard any need for the engines thrust to overcome any rearward motion of the plane. Even if you can't agree with the logical argument for this then agree with the illogical one that if the plane did begin to move backwards then the conveyor belt would oppose it by beginning to move forwards

Given that we are told the air is still, aren't groundspeed and airspeed the same? At what point do they become different?

dont confuse them! lol

[Sancho]

when you walk along the ground, does the ground move?

no, but it still goes backwards the same speed your walking.

do you understand this?

I think you're alone on understanding that.....

[dieselboy]

I think you're alone on understanding that.....

well if the ground didnt move away from you, then only one of the two things will be happening:

the ground is following you, or,
your not actually going anywhere in the first place.


chillitt and slugsie are Right, but they dont know why :/

[nero279]

dont confuse them! lol

mate, i'm still saying it will take off! Who's confused?

[dieselboy]

mate, i'm still saying it will take off! Who's confused?

but can you explain why

[Sancho]

well if the ground didnt move away from you, then only one of the two things will be happening:

the ground is following you, or,
your not actually going anywhere in the first place.

Or the ground (or Tescos) stays exactly where it was and you move away from it.....

[Sancho]

but can you explain why

Because the engines move the air over the wings and it creates lift.

[nero279]

but can you explain why

20 odd pages ago somewhere I did

[dieselboy]

Because the engines move the air over the wings and it creates lift.

lol, no they dont.

see fig. 1

[Slugsie]

chillitt and slugsie are Right, but they dont know why :/

I know exactly why I am right thanks.

[nero279]

GAWD this is painful

The aircraft accelerates not because the wheels are driven but because of the thrust generated by the engines, assuming the brakes are released the wheels are free to do WTF they like, the conveyor has no effect on the planes speed, just the speed of the wheels as they are not what's driving the plane. So the plane accelerates at it's normal rate, and takes off as normal.

The wheels are freewheeling, the fact that the conveyor belt is running at the opposite speed to the plane means the wheels freewheel twice as fast, but the fact that they are still freewheeling and never driven means it has no effect on the planes acceleration.

The acceleration is down to the air movement or thrust of the engines not because the wheels are being driven.

C'mon guys think about it, the fact that the wheels are freewheeling means there's no transfer of force between the conveyor and the body of the plane, the conveyor's force is acting on the wheels.


Conversely the propulsion generated by the planes engines does act on the body of the plain, meaning the plane must accelerate.


Relative to a fixed point or relative to the conveyor, airspeed/groundspeed, whatever, it has no bearing.

[Sancho]

lol, no they dont.

see fig. 1

Are they entirely ornamental then?

[dieselboy]

I know exactly why I am right thanks.

so explain it then.
explain that the conveyor wont be moving at all, and why.