conveyor belt and plane answered at last ??

[crank39]

Joe, your from nottingham, shouldn't you be out nicking peoples washing by now

 

[doitall]

Why are you lot so dumb? The plane is propelled forward because Newton's Law of Motion says it must be. The only difference between taking off on a runway and a conveyor is that on the conveyor the wheels would turn at twice the speed. But so bloody what?

Because in the original question the wheels must match the speed.

 

[joe-90]

Yes and so they will rotate at twice the speed. The plane has a contract with the air - not the floor.

 

[doitall]

Yes and so they will rotate at twice the speed. The plane has a contract with the air - not the floor.

How many more times do I need to say it.

"The wheel have to match the speed not go twice as fast."

 

[joe-90]

The only time the wheels match the speed is when they are stationary.

 

[doitall]

The only time the wheels match the speed is when they are stationary.

Nearly got it joe90.

Now put your toy plane on the Tesco conveyor and hang on tight.

What are the wheel doing even though the plane is static.

Now can you push the plane up the belt without the wheels going faster than the belt.

Nope, so the plane can't take off.

 

[joe-90]

That wasn't the original premise of the question.

 

[doitall]

That wasn't the original premise of the question.

Yes it was, the speed had to match the conveyor.

The plane needs an air speed to take off, which means it has to go faster than the conveyor.

When I'm sat on Bristol Lulsgate ready to take off, the revs are increased to 2400, take the hand brake off and were rolling (that means the wheels are going round) at an air speed of 85knots we have lift off, with any luck.

Now lets say the magic tarmac is moving at 85knots, all things being equal I'm not going anywhere.

 

[joe-90]

It's got nothing to do with the wheels. If the wheels don't turn at double the speed - then you have no question. It's not viable. No point discussing it.

 

[Deleted member 63160]

That wasn't the original premise of the question.

Yes it was, the speed had to match the conveyor.

The plane needs an air speed to take off, which means it has to go faster than the conveyor.

When I'm sat on Bristol Lulsgate ready to take off, the revs are increased to 2400, take the hand brake off and were rolling (that means the wheels are going round) at an air speed of 85knots we have lift off, with any luck.

Now lets say the magic tarmac is moving at 85knots, all things being equal I'm not going anywhere.

If the wheels had brakes on I'd agree. If not they'll just spin at 170knots till you get off the floor surely.

 

[joe-90]

Don't call he Shirley - we don't want a row.

 

[doitall]

Yes mitch but they ain't allowed to in the context of the problem.

 

[joe-90]

It's all down to the third of Newton's laws of motion.

The engines are active, the wheels are passive.

When the engine thrusts then an equal and opposite reaction is a property given to the engines. The engines are fixed to the plane and take it with it.

The wheels are passive and play no part.

It's schoolboy physics.

 

[hansthebear]

Aircraft with landing gear down, stationary on a conveyor, then a 300mph headwind hits it and the landing gear is retracted, what happens?


Ooooooooooooh!

 

[doitall]

It's got nothing to do with the wheels. If the wheels don't turn at double the speed - then you have no question. It's not viable. No point discussing it.

We know it's not viable but it's the rules laid down in the problem.

The plane can't take off, and it has every thing to do with the wheels, because they are what the plane is sat on and has to match the conveyor speed.

It doesn't matter what anything else is doing, if the wheels and belt match speeds the toy is stationary.