Physics Puzzle

[markie]

It's nice to see bas back,

PS is this still going, why don't we ask Richard Branson to try it out, he's got the planes, now all he needs is a con belt a few miles long,

 

[Zampa]

Still waiting for an answer...

 

[ban-all-sheds]

Zampa - how many people have to say "yes it will take off" before you realise that you've had an answer?

 

[kendor]

the way i read the question is that the plane will always be static as the floor moves , therefore there will be no flow of air over the wings and no lift so no is the answer it will never take off. whether it's a jet or prop a propellor plane would still need forward motion on top of any backdraft from the props in order to take off.

 

[empip]

Done to death mate.

I would be be more concerned with 'fly-by-wireless' ..... We have had 'fly-by-wire'........

A plane with no wires or mechanical connections between its engine, navigation system and onboard computers - only a wireless network - is being built by engineers in Portugal.

Ok 'til the Archers come on or worse 'The Strolling Bones' ..
Throttle position "zzt zzt ... brown sugarrrr ".. Badooom !

 

[ban-all-sheds]

the way i read the question is that the plane will always be static as the floor moves.

How on earth do you arrive at that conclusion?

 

[kendor]

the way i read the question is that the plane will always be static as the floor moves.

How on earth do you arrive at that conclusion?

The plane starts to move as thrust is applied but then the runway matches the speed that the wheels were revolving at , so the plane eventually is static ie not moving through the air the planes wheels will revolve if they didn't then for a second the plane would go backwards until the runway sensed the change in speed of the wheels, whatever means of sensing whether tachometer looking at the wheels or some other means there will be a slight lag until the runway matches the wheel speed.
but whatever happens the plane should be relatively static in air space.
Explained ok?

 

[hermes]

now all he needs is a con belt a few miles long,

The belt only needs to be 150 metres long.

 

[empip]

now all he needs is a con belt a few miles long,

The belt only needs to be 150 metres long.

Put a 'twist in it' and use both sides for the same price Cheers August Ferdinand M

 

[ban-all-sheds]

the way i read the question is that the plane will always be static as the floor moves.

How on earth do you arrive at that conclusion?

The plane starts to move as thrust is applied but then the runway matches the speed that the wheels were revolving at , so the plane eventually is static ie not moving through the air the planes wheels will revolve if they didn't then for a second the plane would go backwards until the runway sensed the change in speed of the wheels, whatever means of sensing whether tachometer looking at the wheels or some other means there will be a slight lag until the runway matches the wheel speed.
but whatever happens the plane should be relatively static in air space.
Explained ok?

No - completely wrong.

The engines are thrusting against the air, not via the wheels to the runway. It doesn't matter whether the runway is static, or moves forwards or moves backwards relative to the wheels in order to make the wheels rotate normally/slower/faster respectively, the plane will still move through the air as normal.

Imagine you are standing alongside a conventional factory conveyor belt, waist high, and on it is a small wheeled cart with high quality low-friction bearings in the wheels.

The conveyor belt is stationary, and you place a hand on the cart and begin to push it along in the opposite direction to that in which the belt normally moves.

As you are walking along, someone starts the conveyor belt.

Explain why you can no longer walk.

 

[ban-all-sheds]

now all he needs is a con belt a few miles long,

The belt only needs to be 150 metres long.

Even if you mean 300m long, i.e. 150m between the end rollers, I'm not sure any of his planes can take off in 150m....

 

[Adam_151]

I'd say it would take off...

...for it not to take off, the belt would have to be dragging it back with the same force (the speed matching is red herring) as the engines are pushing it forward through the air with (or at least enough to stop it reaching a high enough velocity to take off)

Even if you had a really strong belt that matched the power of the engines it wouldn't work, for the power from the belt is being applied to the plane through the wheels, which would just spin rather transmit the power into backwards drag on the plane

(sorry if this has already been said, skim read it, saw very similar, but not phrased as clearly as this )

 

[hermes]

Explain why you can no longer walk.

Because if you could walk, the belt would no longer be keeping up with the wheels.

 

[hermes]

now all he needs is a con belt a few miles long,

The belt only needs to be 150 metres long.

Even if you mean 300m long, i.e. 150m between the end rollers, I'm not sure any of his planes can take off in 150m....

No, 75m between rollers. If the belt is moving at the speed of the wheels then the plane's not going anywhere.

 

[Adam_151]

If the belt is moving at the speed of the wheels then the plane's not going anywhere.

Would you be be happy standing in front of the end of the belt then?