Off topic - a little puzzle

blimey...plane needs airflow to take off so its got f all to do with f all else ....the way i see it///if conveyer belt keeps track of plane speed and therefore keeps it reletivly stationary to air flow then the clart wont ever take off.....

[Alpineandy]

Actually that's an irrelevant question, if you understand the answer.

No, It's the only relevant bit...

This is a very very old question (I heard it around 10 years ago).

2 scientists can argue for and against and still not agree on the answer because it's an imposible question... But the 2 alternatives are

1) yes the aircraft would take off, eventually the thrust from the engines will counter the push of the conveyor belt. The wheels will spin at an infinite speed, but this will not push the aircraft back, the force of the engines will move the aircraft forward and it will eventually take off normally. The aircraft will continue to move forward at takeoff speed, but the wheels may well be spinning at 1000+ mph

OR

2) No, the plane will not takeoff. The reason? Relative wind.
Planes make lift by air moving over the wings. Whether the wind is blowing, or the engines pushing the plane forward, air is moving over the wings to provide lift.
If you are stationary on a conveyor belt, there is absolutely no wind moving over the wings, and hence no lift.

I don't know the answer (and anyone that thinks they do is making assumptions), but It comes down to 'do you believe it can get to the correct airspeed (speed of the air over the wings) to generate enough lift'.

Here's another one which doesn't need physics :
How long is this piece of string?

How long is this piece of string?

It's as long as it is.

thats right. the wing relies on the air flowing faster over the top to create vacum and lift. now if the belt manages to speed up the air under the wing enough, the plane might never take off.

1) yes the aircraft would take off, eventually the thrust from the engines will counter the push of the conveyor belt.

No, this is a flawed statement. The conveyor belt does not apply a force on the plane, any more than a treadmill applies a force on you if you were wearing rollerskates.

[Alpineandy]

No, this is a flawed statement. The conveyor belt does not apply a force on the plane, any more than a treadmill applies a force on you if you were wearing rollerskates.

It does apply drag though (probably not much). On top of this the wheels would in theory be travelling at twice the speed of the plane and to reach take off speed that would exceed the safe speed for the tyres, and planes don't take off easily when the tyres blow out.

Does this mean it's the wrong answer..... I don't know

I'm more interested in this runway sized conveyor belt That is a humongous piece of civil engineering ,where is it ??

It does apply drag though (probably not much). On top of this the wheels would in theory be travelling at twice the speed of the plane and to reach take off speed that would exceed the safe speed for the tyres, and planes don't take off easily when the tyres blow out.

Does this mean it's the wrong answer..... I don't know

NOW you're getting it.

In theory, the plane will take off, with the wheels spinnning twice as fast, and the engine(s) needing to apply *slightly* more thrust to counterract the extra friction.

In practical terms the tyres would have to be pretty special, yes. But it's a simple physics question IMO.

I'm more interested in this runway sized conveyor belt That is a humongous piece of civil engineering ,where is it ??

Its the M25...

No matter what I do I seem to be going nowhere, and eventually I end up in the same place.....

[Alpineandy]

In practical terms the tyres would have to be pretty special, yes. But it's a simple physics question IMO.

There are also questions about the conveyor movement dragging the vacuum (that would create the lift) away from the back of the wing....

IMO too many variables/imponderables to say yes or no.

IMO too many variables/imponderables to say yes or no.

If you can't say yes or no, what can you say?

IMO too many variables/imponderables to say yes or no.

If you can't say yes or no, what can you say?

That it's in line with current government policies .....................

[Alpineandy]

IMO too many variables/imponderables to say yes or no.

If you can't say yes or no, what can you say?

Maybe