Earth spinning

mollymoo said:
Even if you reversed the treadmill and made it go a million miles an hour all that would happen is the wheels would spin faster, the planes speed would still be determined by the jets.
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No. The treadmill would empart a rearwards force on the plane.

Imagine standing with roller skates on a treadmill holding onto the sides. Yes you would be fine if the treadmill was going at 20mph but do you guys seriously believe that it would be just as easy to hold yourself on the treadmill if it was traveling at 20,000mph?
 
mollymoo said:
If you stop or even speed up the treadmill the plane will still travel at the speed the jets are making it go. Even if you reversed the treadmill and made it go a million miles an hour all that would happen is the wheels would spin faster, the planes speed would still be determined by the jets.
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In the confines of the question it is impossible for the wheels to move faster than the treadmill!
 
JBod said:
Because it is moving through the air, it doesn't matter how much you make the treadmill spin the plane will always take off (assuming frictionless wheels of course).
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And that's just the thing. We are not assuming frictionless wheels.
 
neodude said:
And that's just the thing. We are not assuming frictionless wheels.
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Regardless of frictionless wheels (I assume we are talking within the wheels bearings not friction between the tyre and treadmill) it would make no difference surely? They would still have to spin faster than the treadmill to move. Which is impossible in the confines of the question.
 
the planes engine is pushing against the air not the ground,

it does not matter what the ground is doing.. (so long as the air is stationary)

(i think thats right)
 
I like this answer:

Think of it this way. If the plane were pulled by cable, it would move forward regardless of what the conveyor belt was doing. Same situation with the plane's propellor or jet engines that work against the ambient air. The conveyor belt only makes the wheels turn faster.
 
Athanor said:
I like this answer:

Think of it this way. If the plane were pulled by cable, it would move forward regardless of what the conveyor belt was doing. Same situation with the plane's propellor or jet engines that work against the ambient air. The conveyor belt only makes the wheels turn faster.
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The wheels would be turning faster than the treadmill in that case.
 
How can they be turning faster than the treadmill when it's the treadmill itself that is making them turn? The wheels can only turn as fast as the treadmill, no more, no less.
 
Would it not still move forward even if the treadmill was running faster than the wheels? (Which I can't think how it could do anyway)
 
Rusty_Noob said:
The wheels would be turning faster than the treadmill in that case.
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Exactly. If the plane is moving forward relative to the stationary air around it then the wheels will be turning faster than the speed of the belt they're on.

However wheel speed has no effect on engine thrust so the plane will accelerate forwards.
 
Athanor said:
I like this answer:

Think of it this way. If the plane were pulled by cable, it would move forward regardless of what the conveyor belt was doing. Same situation with the plane's propellor or jet engines that work against the ambient air. The conveyor belt only makes the wheels turn faster.
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No. In the confines of the question the wheels cannot be going faster than the treadmill. In the case of a cable the same is true. What would happen is you would get an almost instant acceleration of both the wheels and the treadmill to a ridiculous speed to the point where the force generated backwards on the plane by the treadmill is enough to snap the cable. This would happen in an instant and the plane wouldn't budge.

Obviously in reality this is ridiculous. But in reality the question is also ridiculous and it would be impossible to get a treadmill that could instantly match the speed of the planes wheels. But that is what the question states. I'm not making up the rules, the question is.
 
How are you guys not getting this?

Like others have stated - the wheels have no drive - the spin freely. When you start the engines up they create forward thrust, yes?

If the forward thrust is enough - the plane will, and I mean, will move forward. Because of the thrust created by the engines. That is a fact. Not an assumption.

It's very simple actually...
 
Rusty_Noob said:
The wheels would be turning faster than the treadmill in that case.
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i see what you are getting at (sounds about right to me)... however

Do not try and rotate the wheels faster. That's impossible. Instead... only try to realize the truth.

....there is no wheels!
 
neodude said:
No. In the confines of the question the wheels cannot be going faster than the treadmill. In the case of a cable the same is true. What would happen is you would get an almost instant acceleration of both the wheels and the treadmill to a ridiculous speed to the point where the force generated backwards on the plane by the treadmill is enough to snap the cable. This would happen in an instant and the plane wouldn't budge.

Obviously in reality this is ridiculous. But in reality the question is also ridiculous and it would be impossible to get a treadmill that could instantly match the speed of the planes wheels. But that is what the question states. I'm not making up the rules, the question is.
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Where are you getting these confines of the question from? The way you are explaining it the wheels of the plane would give out long before the cable snapped.
 
Ice On Fire said:
How are you guys not getting this?

Like others have stated - the wheels have no drive - the spin freely. When you start the engines up they create forward thrust, yes?

If the forward thrust is enough - the plane will, and I mean, will move forward. Because of the thrust created by the engines. That is a fact. Not an assumption.

It's very simple actually...
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We know the wheels have no drive. But for the plane to move forward the wheels are required to turn. A plane with it's brakes on is not going anywhere (Unless it is a fighter or light aircraft that has a high power-weight ratio and can overcome the friction).

The question states that the treadmill WILL EXACTLY MATCH the speed of the wheels. In this case it is impossible for the plane to roll forward on it's wheels.
 
neodude said:
No. In the confines of the question the wheels cannot be going faster than the treadmill. In the case of a cable the same is true. What would happen is you would get an almost instant acceleration of both the wheels and the treadmill to a ridiculous speed to the point where the force generated backwards on the plane by the treadmill is enough to snap the cable. This would happen in an instant and the plane wouldn't budge.

Obviously in reality this is ridiculous. But in reality the question is also ridiculous and it would be impossible to get a treadmill that could instantly match the speed of the planes wheels. But that is what the question states. I'm not making up the rules, the question is.
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No the wheels can go backwards and the plane wil lstill take off, they're free spinning.


 
JBod said:
Where are you getting these confines of the question from? The way you are explaining it the wheels of the plane would give out long before the cable snapped.
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Probably yes.

The question comes from the original question posted by Borden...

"If an aeroplane was sat on a treadmill that was moving in the opposite direction at the same speed the wheels were moving, would it be able to take off?"

Which is the one I'm arguing against.
 
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