Maybe it's windy.
Notice how it says "Airflow"? There will be none if the plane is stationary!
Everyone in favour of lift-off: Back to school!
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Plane Problem
- Thread starter Mr.Russian
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We all know that air moving over the wings generate lift, but the wheels don't generate the forward momentum. Eventually, the thrust of the engines will be more powerful then the pull of the wheel on the treadmill. At that point the plane will start to move forward and eventually, regardless of how much the treadmill tries to keep up. The plane will go fast enough to take off.
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The question sais it is a very cleverly designed treadmill...
It doesn
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And back in the 1800s they thought going faster then 30km/h in a train would make the human body explode. Just cause it's not built yet, does not mean it won't work
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And back in the 1800s they thought going faster then 30km/h in a train would make the human body explode. Just cause it's not built yet, does not mean it won't work
It isn't about whether it could be built. It's the fact that anything built strong enough to support the mass of a jet liner. Would be too massive to move and accelerate at those speeds. It would have to weigh many tons. There would be too much mass involved and the g forces exerted on the tread would be too great. It would tear itself apart before it reached the speed of a jet liner's maximum thrust. Regardless of what you built it of, or how cleverly designed it was.
This isn't about what people thought in the 1800's. You can't defy the laws of physics.
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The treadmill is a part of the equation. Without it, you have no problem.
Ok, here's one for you. If you can build a treadmill that can go that fast. I can build frictionless bearings for the jet's wheels. Then it doesn't matter if your treadmill can move at the speed of light. My wheels will have no effect on the jet. The jet will use it's thrust to push itself forward while the wheels spin freely on the mill.
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Thats exactly why the treadmill is not the problem!
We just have to assume it's possible.
Your frictionless bearings/can we build a giant treadmill are a whole different problem.
Someone give me $2000 and I will buy a treadmill and a model plane any try it out!
We just have to assume it's possible.
Your frictionless bearings/can we build a giant treadmill are a whole different problem.
Someone give me $2000 and I will buy a treadmill and a model plane any try it out!
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Ok, so your treadmill is assumed possible but my frictionless bearings are not? Both defy the laws of physics therefore both are equally valid. My jet with frictionless wheel bearings will take off. No matter how fast your treadmill moves. It's as simple as that.
You can't test it in reality because no tread mill could accelerate at the speeds necessary to keep up with the acceleration of the model plane.
You can't test it in reality because no tread mill could accelerate at the speeds necessary to keep up with the acceleration of the model plane.
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Same problem as trying to lift off on a CV.
If it is moving fast, you will have to match a much lower take-off speed than when it's standing still (the latter is one of the more advanced training missions in Pacific Fighters).
All what counts is the relative speed towards the air.
Carrier moving plus plane moving into the same direction=higher relative speed towards the air.
The relative speed of the AC to the CV is still the same as if the ship was standing still.
Try moving in a subway (or on a escalator):
If you are moving towards the same direction, your speed gets added to that of the train compared to that of the environment.
Move in the opposite direction, your overall speed gets reduced by the amount of your movement relative to the train.
Since the treadmill is in a fixed position towards the environment (which we also include the air in), and it is "moving" the exact opposite speed of the plane (same amount, just negative), that makes a zero speed towards the environment.
Unless there's a huge tempest going on, the air won't move over the wings, no updraft is being created, hence no flying.
EDIT:
Of course it has all to do with friction.
Without friction towards the treadmill, the plane would not get pushed back.
You cannot apply force over surfaces without friction.
If there was no friction, it would be as if it floated in the air (think saucer or whatever).
When it has no contact to the treadmill it will also not get affected.
Obviously, for this example to work, the wheels will always have to have static friction.
Once they get into dynamic friction (meaning no longer are 100% of the backwards force of the treadmill transfered into the plane) the plane will move forward, that will induce some uplift, the friction will become even less and so forth.
If it is moving fast, you will have to match a much lower take-off speed than when it's standing still (the latter is one of the more advanced training missions in Pacific Fighters
).All what counts is the relative speed towards the air.
Carrier moving plus plane moving into the same direction=higher relative speed towards the air.
The relative speed of the AC to the CV is still the same as if the ship was standing still.
Try moving in a subway (or on a escalator):
If you are moving towards the same direction, your speed gets added to that of the train compared to that of the environment.
Move in the opposite direction, your overall speed gets reduced by the amount of your movement relative to the train.
Since the treadmill is in a fixed position towards the environment (which we also include the air in), and it is "moving" the exact opposite speed of the plane (same amount, just negative), that makes a zero speed towards the environment.
Unless there's a huge tempest going on, the air won't move over the wings, no updraft is being created, hence no flying.
EDIT:
Of course it has all to do with friction.
Without friction towards the treadmill, the plane would not get pushed back.
You cannot apply force over surfaces without friction.
If there was no friction, it would be as if it floated in the air (think saucer or whatever).
When it has no contact to the treadmill it will also not get affected.
Obviously, for this example to work, the wheels will always have to have static friction.
Once they get into dynamic friction (meaning no longer are 100% of the backwards force of the treadmill transfered into the plane) the plane will move forward, that will induce some uplift, the friction will become even less and so forth.
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In fact, it's not quite that simple - the shape of the wings means that the air pressure above the wing is slighlty lower than that below, lifting the wing up. This only happens above a certain speed of the wings relative to the air (stall speed). This plane is not moving relative to the air. It will never take off. QED.
The plane on the conveyor will never take off and anyone who thinks otherwise needs to get themselves back to school PDQ.
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Wait! That's it! The friction of the wheel bearings isn't great enough to stop the plane! The thrust of the engines will continue to push the plane forward. Even if the treadmill could move and accelerate to infinity. It would just continue to accelerate trying to keep up with the jet. The wheels would just keep spinning faster and faster. So would the treadmill. The forward thrust of the jet engines would still push the jet forward. If the treadmill is long enough. The jet would eventually take off.
That, or the wheel bearings would burn up and the plane would crash on the mill. If the treadmill can survive it though, the jet should be able to too.
That, or the wheel bearings would burn up and the plane would crash on the mill. If the treadmill can survive it though, the jet should be able to too.
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