Yes, I am assuming that there is friction between the belt and the wheels and that the conveyor belts bearings are frictionless. I suupose we need to agree on what kind of belt it is. Is it one like a fan belt or is it a series of rollers? Again, I assumed it was like a fan belt since the airplanes wheels would get stuck between the rollers.
Totem
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Tee hee, Totem has the mental block that makes people get this wrong.
I should rephrase what I said, because it's not 100% accurate. If the conveyor belt is frictionless, then the wheels don't even spin. They would just slide along it without ever rotating, even as the plane moves.
Bear with me, I'm trying to figure out the best way to explain this.
Okay here's the disconnect:
The rotation of a plane's wheels has no effect upon its motion in any direction. The reason for this, is that there is no means by which a tangential force applied to a free wheel can be transferred to the axle.
It's not like a car, where the rotation of the wheels is deliberately connected to other parts. In a car, the force applied by the engine is specifically transferred through the parts to indirectly rotate the wheels. But a plane has no such connection between engine and wheel.
Thus, every force that the wheel is subjected to is returned in the form of wheel rotation, but the transfer of force ends there. The wheel rotates around the axle, but impacts it in no way.
(In reality, there is going to be a small amount of friction there which would slightly affect the results, but it's negligible).
So the conveyor moves, and the wheels move relative to it. But even with that friction, the plane as a whole is unaffected, because the forces do not extend beyond the wheels. Disregarding that small amount of friction with the axle, they're just spinning, and the plane is sitting in place.
With the engines on, then the plane as a whole is subjected to a force. The engines push the air around the plane, and the engines are directly connected to the plane's body. So the plane moves forward along the conveyor belt, and can take off as it normally would further down it. The increasing speed of the plan causes the wheels to rotate with increasing speed, but this has no effect.
I don't know if I can put it better than that. Gotta go play basketball now though, so adios.
Edited, Jul 26th 2006 at 5:53pm EDT by Eske
Bear with me, I'm trying to figure out the best way to explain this.
Okay here's the disconnect:
The rotation of a plane's wheels has no effect upon its motion in any direction. The reason for this, is that there is no means by which a tangential force applied to a free wheel can be transferred to the axle.
It's not like a car, where the rotation of the wheels is deliberately connected to other parts. In a car, the force applied by the engine is specifically transferred through the parts to indirectly rotate the wheels. But a plane has no such connection between engine and wheel.
Thus, every force that the wheel is subjected to is returned in the form of wheel rotation, but the transfer of force ends there. The wheel rotates around the axle, but impacts it in no way.
(In reality, there is going to be a small amount of friction there which would slightly affect the results, but it's negligible).
So the conveyor moves, and the wheels move relative to it. But even with that friction, the plane as a whole is unaffected, because the forces do not extend beyond the wheels. Disregarding that small amount of friction with the axle, they're just spinning, and the plane is sitting in place.
With the engines on, then the plane as a whole is subjected to a force. The engines push the air around the plane, and the engines are directly connected to the plane's body. So the plane moves forward along the conveyor belt, and can take off as it normally would further down it. The increasing speed of the plan causes the wheels to rotate with increasing speed, but this has no effect.
I don't know if I can put it better than that. Gotta go play basketball now though, so adios.
Edited, Jul 26th 2006 at 5:53pm EDT by Eske
So you are operating under the assumption that the plane can move itself regardless of the friction (or lack of it). I am using something along the analogy of a car attempting to accelerate on a sheet of ice. It doesn't. The wheels just spin. This is empiracally provable. A plane is just a car with weird appendages until lift is formed.
Think of it this way: On a dyno test vehicles are revved on roller bearings to mimic getting the vehicle up to speed under realistic conditions. All this is is a dyno test made large. Simple, neh?
Totem
Think of it this way: On a dyno test vehicles are revved on roller bearings to mimic getting the vehicle up to speed under realistic conditions. All this is is a dyno test made large. Simple, neh?
Totem
Totem wrote:
So you are operating under the assumption that the plane can move itself regardless of the friction (or lack of it). I am using something along the analogy of a car attempting to accelerate on a sheet of ice. It doesn't. The wheels just spin. This is empiracally provable. A plane is just a car with weird appendages until lift is formed.
Think of it this way: On a dyno test vehicles are revved on roller bearings to mimic getting the vehicle up to speed under realistic conditions. All this is is a dyno test made large. Simple, neh?
Totem
Think of it this way: On a dyno test vehicles are revved on roller bearings to mimic getting the vehicle up to speed under realistic conditions. All this is is a dyno test made large. Simple, neh?
Totem
No no no. A plane is not a car with wings on it. A car derives motion from interaction of forces with the ground beneath it. A plane derives motion from the interaction of forces between the engines and the air that they push off.
Anyways, I edited my above post. Perhaps it will clarify.
Edited, Jul 26th 2006 at 5:55pm EDT by Eske
Argh. The lightbulb just went on. I was mixing two different driving mechanisms in my mind. I was wrong. You are right.
I hate it when that happens.
Totem
I hate it when that happens.
Totem
On monday I was going to comment on my surprise that this thread still lingered like a herpes scar at the top of the page, but decided that the condescending nerd-types were better contained in one thread anyway. It's a pity that with Tote's concession this will probably fall to the second page and leave you bunch of twats longing for a new purpose, to be expressed in some other topic of random theorizing. Even when symptoms are not visible, you can still infect your partners, remember that.
Will it go 'round in circles?
Will it fly high like a bird up in the sky?
Will it fly high like a bird up in the sky?
In a time of universal deceit, telling the truth is a revolutionary act.
Great tune, Sammy.
Totem
Totem
I think Eske and Totem's conversation actually clarifies this a lot more than the SD article. The critical difference of a plane not being a car with wings is what makes the whole thing so counterintuiative.
It's ok Totem. We all know that helicopters get their driving force from the electro magnets linging the landing gear. It's easy to see how someone could get confused when subject to EM forces that strong for such long periods.
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