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Plane Problem

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#321
BuddyLee said:
The ground is not moving, the surface of the treadmill is. As well as the surface of the tires. The ground only moves in relation to the body of the plane after the engines thrust it forward, or the plane puts on its brakes.
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That's exactly it. The plane is sitting on the tread, not the ground. As long as the tread is moving backwards at the same speed the jet is moving forward. The jet cannot move forward in relation to the ground. It is moving forward in relation to the tread mill.


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The car on the tread mill in the drawing above. Is turning it's wheels at the same speed as the tread. If you move the car forward on the tread. The wheels are spinning faster than the tread is. Even if it is only slightly more.

However the tread mill is designed to counter that movement. So it would speed up too. Your hand on the car is an outside force. If you continued to pull it forward the tread mill could accelerate to infinity and it couldn't pull the car back. You are moving it forward.

If the car is moving under it's own power. It has to mantain the speed it is moving on the tread, on it's own. So if the engine tries to pull the car/plane forward. The tread mill speeds up to compensate. Again resulting in zero net movement.
 
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#323
melipone said:
The treadmill speeding up only speeds up the wheels - it has no relation to the speed of the plane. Thats how I understand it atm anyway. It can speed up all it wants but its only going to make the wheels go round faster in addition to the rotation provided by the thrust.
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The treadmill is not turning the wheels. The thrust of the planes engines are pushing the wheels forward, but this forward movement is countered by the reverse movement of the tread.

So as long as the treadmill can counter the forward movement on the wheels generated by the thrust of the engines. The plane cannot move forward in relation to the ground.

It is moving forward in relation to the tread, but the tread is moving exactly the same speed in the opposite direction. So the plane does not move in relation to the ground.

The more thrust you add. The more it is countered by the reverse movement of the tread. Resulting, again, in zero net movement for the plane.
 
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#324
User Name said:
The treadmill is not turning the wheels.
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How is it not turning the wheels? Without a force applied to the plane what do you think will happen? It will stay still (for the sake of the experiment anyway). This means the wheels are turning at the speed of the treadmill. Apply the thrust so that the plane is moving at say 300mph and the tread speeds up too but it doesn't counter the speed of the plane - it is negated always by the wheels turning faster. The wheels just go round faster when the treadmill tries to compensate for the increased plane speed.

The treadmill and plane start off at rest. Now as force is applied to develope some speed, the treadmill matches the speed and makes the wheels go round faster. Thats all it does I think.
 
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#326
melipone said:
How is it not turning the wheels? Without a force applied to the plane what do you think will happen? It will stay still (for the sake of the experiment anyway). This means the wheels are turning at the speed of the treadmill. Apply the thrust so that the plane is moving at say 300mph and the tread speeds up too but it doesn't counter the speed of the plane - it is negated always by the wheels turning faster. The wheels just go round faster when the treadmill tries to compensate for the increased plane speed.

The treadmill and plane start off at rest. Now as force is applied to develope some speed, the treadmill matches the speed and makes the wheels go round faster. Thats all it does I think.
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The jet has a force applied to it. That is the jet engine's thrust. If the tread were not moving. The plane would roll forward and take off. If the engines were not generating thrust. The plane would sit on the tread as the tread moved backwards.

Since the forward movement of the jet's thrust is being countered by the reverse movement of the tread. All the plane can do is stay right where it is. If it generates more thrust. It moves faster on the tread, but the tread mill is designed to counter that by increasing the speed of the tread.

All this results in no net movement of the plane. Since it's forward movement is constantly countered by the rearward movement of the tread.
 
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#327
User Name, how can you not understand that wheels are designed to turn, and that the treadmill just turns the wheels, exerting very little if any force on the actual body of the plane? It's REALLY SIMPLE.

Ok ok. Simple example.

GET A CYLINDRICAL OBJECT. ROLL IT BETWEEN YOUR TWO HANDS. THINK ABOUT THE FORCES.

If you move one hand faster, the object will go in the direction that that hand is moving in, right?

Because only a small percentage of the treadmill's total force actually goes into friction inside the wheel bearings, the force pushing the plane forward is much greater than that pushing it backward.
 
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#328
Lizardhands said:
User Name, how can you not understand that wheels are designed to turn, and that the treadmill just turns the wheels, exerting very little if any force on the actual body of the plane? It's REALLY SIMPLE.

Ok ok. Simple example.

GET A CYLINDRICAL OBJECT. ROLL IT BETWEEN YOUR TWO HANDS. THINK ABOUT THE FORCES.
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The jet is rolling the wheels not the tread. The jet is moving on the spinning wheels in an attempt to move forward. It does this by generating thrust. This forward movement is countered, however, by the reverse movement of the tread.

So the plane maintains it's position relative to the ground by rolling forward on the reverse moving tread. Again, no net movement by the plane.
 
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#332
[CoR]MiccyNarc said:
User name, take a pen, roll it between both your hands. Move both your hands at the same speed. Note how fast the pen rolls. Now move just one hand. Compare how fast the pen rolls. Half as fast, right? Right.

If you don't get this, well, just GTFO the internet and go to school.
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If you move your hands the same speed. The pen rolls between your hands, but it doesn't move anywhere. It maintains it's location in space. The same is true for the plane.

The forward thrust of the jet engines move it foward. The reverse moving tread moves the plane backward. The thrust and the moving belt cause the jet to act just like the pen in your hands. Niether the thrust of the engines, or the movement of the tread. Can change the planes location in space.

All they can do is stop the other from moving it.
 
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#334
Lizardhands said:
User Name, don't think of the wheels as part of the plane. Think of them as something between the treadmill and the plane which is used to vastly reduce friction between treadmill and plane.

One hand is treadmill. One is plane. The pen is wheels. Look at it that way.
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The wheels are a part of the plane. They just spin. If the plane moved forward. The wheels would spin faster then the tread is moving. Since the tread mill compensates for this, by moving the tread faster. The plane would have to generate more thrust in order to move forward.

If the tread mill can manage to compensate for the thrust of the jet rolling on it's wheels. To the point where jet engines reach their maximum thrust. The plane will never move forward, in relation to the ground. It will sit in one spot. Spinning it's wheels forward on a reverse moving tread.

It will never actually go anywhere.
 
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#335
User Name said:
The wheels are a part of the plane. They just spin. If the plane moved forward. The wheels would spin faster then the tread is moving. Since the tread mill compensates for this, by moving the tread faster. The plane would have to generate more thrust in order to move forward.

If the tread mill can manage to compensate for the thrust of the jet rolling on it's wheels. To the point where jet engines reach their maximum thrust. The plane will never move forward, in relation to the ground. It will sit in one spot. Spinning it's wheels forward on a reverse moving tread.

It will never actually go anywhere.
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the treadmill compensates the speed of the plane , not the speed of the wheels

ok, having that said, the speed of the treadmill is still irrelevant
 
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#336
worluk said:
the treadmill compensates the speed of the plane , not the speed of the wheels

ok, having that said, the speed of the treadmill is still irrelevant
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The speed of the tread mill is irrelevant. It isn't moving. The tread on the mill is. It exactly matches the speed of the jet. By moving in exactly the opposite direction. So it prevents the plane from actually moving anywhere.

Sure it's moving forward on the tread, but the tread is moving at the exact same speed in the opposite direction. They are both on a stationary platform. So the jet is stationary in relation to everything except the tread.
 
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#339
User Name said:
The speed of the tread mill is irrelevant. It isn't moving. The tread on the mill is. It exactly matches the speed of the jet. By moving in exactly the opposite direction. So it prevents the plane from actually moving anywhere.

Sure it's moving forward on the tread, but the tread is moving at the exact same speed in the opposite direction. They are both on a stationary platform. So the jet is stationary in relation to everything except the tread.
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the tread does not have any(in a theoretical view) or at least few (in a practical view) impact on the plane since it is its wheels that are turning with the tread. The reference system the engines interact with is the surrounding air, not the ground. But hey, you didnt accept the rollerskates example, why would you accept this...

you will never understand it, you can find it explained in about 30 different way why the plane lifts off, also with references to other forums where you will find another (at least) 50 descriptions. Im sorry.

thanks for your time and good night


[RO]schneidzekk said:
Hint: The wheels will not spin faster or slower than the tread mill.
Click to expand...
In fact they will, as I showed about 3 times already :)
 
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