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Post by Vashthestampede on Dec 7, 2005 20:48:58 GMT -5
Yes but even if the treadmill is matching the speed of the plane its only affecting the wheels which have no affect on the plan being thrust forward.
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Post by MerrSonn on Dec 7, 2005 20:49:40 GMT -5
So theoretically, let's say for a second that the the plane can take off. It starts at a stop and speeds up gradually, but doesn't move anywhere because the runway is constantly moving the other way at the same speed. Finally, the jet lifts off... and then what? It just hovers there? I don't think so...
I'm gonna have to go with no for a number of reasons. Although I do like pie quite a bit...
EDIT: For whatever reason, I was assuming that the conveyor belt was short, definitely not long enough for the plane to take off if the conveyor belt wasn't moving. After rereading the original question, I'm changing my answer to YES.
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Post by Vashthestampede on Dec 7, 2005 21:23:15 GMT -5
The conveyor simply matches the wheel speed no where does it say it will remain stationary.
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Post by MerrSonn on Dec 7, 2005 21:35:08 GMT -5
I was just referring to the length of the runway, for some reason I thought that it was relatively short. I don't know where I got that from.
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Post by jestertls on Dec 8, 2005 3:25:59 GMT -5
Okay, if the plane is on a conveyor and the conveyor matchs the speed on teh plane. The plane is there fore not moving. The plane has to has lift, the air force under teh wings. If nothign in the equation changes like the conveyor stops, or the conveyor is on a mobil unit that is traveling in the same direction of the plane, or a hurricane blows up with enough force to lift the plane in to the air, then it aint going anywhere.
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Post by squirrel on Dec 8, 2005 8:55:17 GMT -5
The jets provide the energy to move the plane. Whether on the ground or in the air, the wheels themselves don't have any motors on them to make them move. I am not sure if they even have brakes to help the plane stop. The fact that the conveyor matches the speed of the wheels, means that the conveyor is matching the speed of the plane that is provided by the engines. The engines are just pushing the plane around, whether on the ground or in the air. The plane takes off when the speed of the airplane is fast enough for the air going over and under the wings generate lift. The jets don't cause flight the wings do
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Post by Vashthestampede on Dec 8, 2005 9:16:29 GMT -5
Yes, but the treadmill is only counteracting the movement of the free spinning wheels so the speed of the wheels themselves is irrelevant to whether or not it attains forward motion.
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Jackson
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Post by Jackson on Dec 8, 2005 15:07:07 GMT -5
I asked a few kids in my physics class today and most of them said that it can't. It's so funny because I KNOW I'm right and they're wrong but they just wouldn't listen to anything.
The forward motion of the plane comes not fromt he interaction on the wheels and ground but between the air and jet engines. The ground, if friction is ignored between the wheels and axels, has no effect on the translational movement of the airplane, just the angular rotation of the wheels. If you consider friction, then the conveyor has a slight effect on the forward movement, pushing it with a small amount of force backwards. This logically isn't enough to completely counter-act the jets. Friction is μN or the coefficient of friction times the Normal force. Speed does not affect the normal force, therefore the amount of resistive friction due to the wheels and axels is constant, no matter what speed the wheels are at. If a plane can take off under normal conditions, then the force of friction doesn't change and therefore it can take off.
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Post by Nowhere on Dec 8, 2005 15:10:11 GMT -5
My answer is yes. It would take off. The thrust generated by the engines would propel the aircraft forward and therefore the airflow over the wings would create lift. The wheels are not a factor here as they are not the driving force. The conveyor would match the speed of the wheels and they would be turning faster, but that is all it would do. It would have to be a long belt = to the normal distance for take off.
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Post by squirrel on Dec 8, 2005 16:21:35 GMT -5
If the plane is not moving in space how is air flowing over the wings, the plane cannot move on the ground because the wheels and the treadmill are moving at the same speed. Because the wheels and treadmill are moving at the same speed the airplane is not moving in relation to the air around it. Since the airplane is not moving through the air no lift can be generated
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Post by Vashthestampede on Dec 8, 2005 16:29:22 GMT -5
Squirrel the wheels do not affect the position of the plane. They are allowed to spin free so there movement is irrelevant to that of the planes.
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Post by squirrel on Dec 8, 2005 16:54:19 GMT -5
On the ground the friction between the wheels and the ground allows the plane to move. On the treadmill the friction is resisted by the motion of the treadmill going in the opposit direction of the direction of the plane. The thrust from the engines are providing the power to move the wheels. Since the wheels and the treadmill spin freely no matter how much thrust the jets provide the aircraft the aircraft will never move in relation to the air around it. The airplane will never take off. Everyone is focusing on the engines providing thrust seperate from the wheels, but on the ground the wheels turning against the ground is what allows the plane to move fast enough to attain the speed to achieve lift (even if the power to make the wheels turn is provided by the thrust of the jet engine). But here the wheels have nothing to turn against, therefore the airplane can't move. Look at it this way take the wheels and the treadmill out of it (they cancel each other out), sit the plane on it's belly on the runway will it take off? With the engines provided on a 747 it will never take off because the plane will never move.
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Post by Vashthestampede on Dec 8, 2005 17:06:38 GMT -5
Yes but the wheels are only there to reduce friction. The speed and direction of there spin does nothing to determine the velocity of the aircraft. The wheels only purpose is to reduce the fricition between the two surfaces.
The jet will move forward. The wheels are not used for thrust in any way shape or form their only purpose is to reduce friction between the two surfaces. The thrust from the engines is not affected by the treadmill so it will move forward, just the wheels will be spinning twice as fast because of the treadmill.
Its a trick question. The question is phrased in such a way as to make it seem the conveyors function is to keep the plane in one position. However this is not the case. The thrust of the engine will move the plane regardless of the runway being a conveyor.
Consider a car on frictionless ice. If a standard motor is used to turn the wheels then the car will definitely not move because there is no friction to cause wheel roll. But if we now strap a jet engine on top of the car, the car will move regardless of the wheels rolling or just sliding. The wheels on a plane serve the same function.
In this case, the plane will move and eventually take off. Assuming the conveyor is the same length as a real runway. And assuming the bearings on the wheels can handle it.
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Post by Jackson on Dec 8, 2005 18:26:55 GMT -5
On the ground the friction between the wheels and the ground allows the plane to move. Then how does an airplane move in the air? There's no friction on the wheels. The friction does NOT make the plane move. In a car where the wheels provide forward motion, friction is needed. An airplane does not use the wheels to achieve forward motion. The thrust from the engines are providing the power to move the wheels. No, the thrust of the engines cause the airplane body to move forward. The wheels spin as a result of touching the ground. Going back to flying in air, if the wheels provide the motion (which they don't) how would in fly in air? Everyone is focusing on the engines providing thrust seperate from the wheels, but on the ground the wheels turning against the ground is what allows the plane to move fast enough to attain the speed to achieve lift. Busted this one above. The wheels move as a result of being in contact with the ground. I'll ask it again, how would a plane fly in the air without the wheels touching the ground? Look at it this way take the wheels and the treadmill out of it (they cancel each other out), sit the plane on it's belly on the runway will it take off? Actually, if you cancel out the wheels and conveyor, then you are left with nothing under the plane, therefore it's flying in air. By placing it on the ground without the wheels and conveyor, you've basically canceled out variable then added another. |
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Post by Kozz on Dec 8, 2005 23:28:45 GMT -5
If it is on the belt, the jet still provides thrust. The air is a constant drag. The plane uses a stationary runway to provide enough air speed over the wings. The conveyer gradually matches the plane's speed. If he ground and the plane are moving at the same speed, then enough air speed will not be possible for lift. Does the question include the plane staying in the same spot? If the conveyor builds up speed at the same rate the plane is in one spot. If i go strap wings to my back and run on my treadmill and gradually increase the speed as I begin to sprint, will I fly? Not really, I've tried for years. I gotta turn off the sigs or something because Vash's slows my computer like mad.
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