Engineering question
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If an airplane is positioned on a conveyor belt as wide as a runway, and this conveyor belt is designed to exactly match the speed of the wheels, but moving in the opposite direction, ... Can the airplane take off?
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If it’s a joke, I don’t get it. If not, the answer is obviously no. Lift is generated by the relative speed of the wings in the air, which in your case is exactly 0. :confused:
Mircea
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I’d argue that it’s the airspeed that matters. If hurricane force winds start blowing during the experiment, the airplane might take off. However the original question didn’t mention anything like that and, under normal conditions, airspeed and ground speed are roughly equal.
Mircea
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Ultimately, I would say: Yes, it will take off. What does the plane care what happens to the wheels? The thrust is there no matter how fast (and which direction...) the wheels are turning. The reason why seaplanes can also take off without wheels :laugh:
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It has nothing to do with either wheels or floats. It can only take off if it is moving forwards at take off speed, relative to the ground. If it is stationary relative to the ground then there will be no lift applied to it.
Lol think again about it :doh: If you are right a rocket can go only if it has wheels :-D Sorry, but the thrust of the jets really has nothing to do with the wheels. And it will moving forward because of the thrust. Easy physics [Edit] It would be another thing in case the wheels are glued on a conveyor belt
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Other thought experiment: a toy car is on a conveyor, you push it forward and the conveyor goes backward "at the same speed" (whatever that means, which is not quite clear). Can you push it forward? Whatever the answer, an airplane would do the same thing, because its thrust is applied in the reference frame of the air around it. The wheels are not driven, they spin freely except when the brake is applied.
harold aptroot wrote:
a toy car is on a conveyor, you push it forward and the conveyor goes backward "at the same speed" (whatever that means, which is not quite clear). Can you push it forward?
Yes, but you might want to rethink about the problem. Derek Muller was able to show that multiple physics professors at prestigious universities didn't even understand the basic underlying principles. A Physics Prof Bet Me $10,000 I'm Wrong It's not exactly the same problem, in the video the propeller will generate a greater force and the vehicle will move forward. Increasing the speed of the conveyor belt will result in an even greater vehicle speed. The wheels are irrelevant. So are university degrees. :-\ Best Wishes, -David Delaune
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Lol think again about it :doh: If you are right a rocket can go only if it has wheels :-D Sorry, but the thrust of the jets really has nothing to do with the wheels. And it will moving forward because of the thrust. Easy physics [Edit] It would be another thing in case the wheels are glued on a conveyor belt
0x01AA wrote:
If you are right a rocket can go only if it has wheels
That has nothing to do with the question. Rockets travel in a vertical direction relative to the ground.
0x01AA wrote:
the thrust of the jets really has nothing to do with the wheels.
I never said it did.
0x01AA wrote:
And it will moving forward because of the thrust.
not if the conveyor belt is counteracting that thrust.
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0x01AA wrote:
If you are right a rocket can go only if it has wheels
That has nothing to do with the question. Rockets travel in a vertical direction relative to the ground.
0x01AA wrote:
the thrust of the jets really has nothing to do with the wheels.
I never said it did.
0x01AA wrote:
And it will moving forward because of the thrust.
not if the conveyor belt is counteracting that thrust.
Quote:
not if the conveyor belt is counteracting that thrust.
Now I come to agree ;) ... but that was never mentioned to be like this :-D [Edit] No it doesn't really matters, it is constructed. Otherwhise you need to explain how 'not if the conveyor belt is counteracting that thrust' can be done in praxis ;) And that would be then only a very consrtucted thing, which has nothing to do with praxis
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It has nothing to do with either wheels or floats. It can only take off if it is moving forwards at take off speed, relative to the ground. If it is stationary relative to the ground then there will be no lift applied to it.
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It has nothing to do with either wheels or floats. It can only take off if it is moving forwards at take off speed, relative to the ground. If it is stationary relative to the ground then there will be no lift applied to it.
Sorry again. If you don't see from what an airplane is driven (and not glued by wheels to the ground especally not to the jets) then I can't help. It is simply physics and there is no need to construct unreal cases.
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If an airplane is positioned on a conveyor belt as wide as a runway, and this conveyor belt is designed to exactly match the speed of the wheels, but moving in the opposite direction, ... Can the airplane take off?
Action - reaction. The wheels won't turn - the conveyor will move with the plane; the forward movement of the wheels moves the conveyor. Nothing is being applied to the wheels; it's only holding the plane up. Along the lines of spaceship thrusters: no friction needed. I think you can assume the conveyor acts as a friction-less surface.
"Before entering on an understanding, I have meditated for a long time, and have foreseen what might happen. It is not genius which reveals to me suddenly, secretly, what I have to say or to do in a circumstance unexpected by other people; it is reflection, it is meditation." - Napoleon I
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harold aptroot wrote:
a toy car is on a conveyor, you push it forward and the conveyor goes backward "at the same speed" (whatever that means, which is not quite clear). Can you push it forward?
Yes, but you might want to rethink about the problem. Derek Muller was able to show that multiple physics professors at prestigious universities didn't even understand the basic underlying principles. A Physics Prof Bet Me $10,000 I'm Wrong It's not exactly the same problem, in the video the propeller will generate a greater force and the vehicle will move forward. Increasing the speed of the conveyor belt will result in an even greater vehicle speed. The wheels are irrelevant. So are university degrees. :-\ Best Wishes, -David Delaune
Funny you would mention that. As a teen, I did an (I think) related experiment, which is easier to think about. The setup is like this. Part A: a small lego (technic) car has a gear (which will act as pinion gear) on one of its axles, and you hold a long rack so that it meshes with the gear on the top. Clearly you can push the little car by pushing the rack, it will go at half the speed that you push it. Part B: if you make a little sliding mount for the rack *under* the gear, can you still push the car? It turns out that you can, and it makes the car go very fast. That is a sort of similar situation as with that propeller car, except instead of wind there is a rack, and instead of a propeller there is a pinion gear that meshes with the rack.
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0x01AA wrote:
If you are right a rocket can go only if it has wheels
That has nothing to do with the question. Rockets travel in a vertical direction relative to the ground.
0x01AA wrote:
the thrust of the jets really has nothing to do with the wheels.
I never said it did.
0x01AA wrote:
And it will moving forward because of the thrust.
not if the conveyor belt is counteracting that thrust.
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Quote:
It has nothing to do with either wheels or floats. It can only take off if it is moving forwards at take off speed, relative to the ground. If it is stationary relative to the ground then there will be no lift applied to it.
Sorry again. If you don't see from what an airplane is driven (and not glued by wheels to the ground especally not to the jets) then I can't help. It is simply physics and there is no need to construct unreal cases.
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Sorry holy shit what?
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That has nothing to do with the question. Rockets travel in a vertical direction relative to the ground.
What? Rockets work only vertical? :doh: :confused: Only nonsense. Stop doing this...
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harold aptroot wrote:
a toy car is on a conveyor, you push it forward and the conveyor goes backward "at the same speed" (whatever that means, which is not quite clear). Can you push it forward?
Yes, but you might want to rethink about the problem. Derek Muller was able to show that multiple physics professors at prestigious universities didn't even understand the basic underlying principles. A Physics Prof Bet Me $10,000 I'm Wrong It's not exactly the same problem, in the video the propeller will generate a greater force and the vehicle will move forward. Increasing the speed of the conveyor belt will result in an even greater vehicle speed. The wheels are irrelevant. So are university degrees. :-\ Best Wishes, -David Delaune
Randor wrote:
Derek Muller was able to show that multiple physics professors at prestigious universities didn't even understand the basic underlying principles.
Along that note, here is one of the worst offenders I've ever seen. Robert Benfer, an anthropology teacher at Missouri, effectively says that once the sun sets, the sky immediately gets dark. Search for the phrase: "Our simulation for that latitude..." I've uploaded an outline of the sky back then at 22° sun depression, highlighting the fox he is talking about. The only way you could say the tail was visible is if you weren't taking twilight into account. If you are going to be studying the astronomy of ancient cultures, understanding twilight should be pretty high on the list of things to comprehend. :laugh: :laugh: :laugh: He even failed to understand when I pointed it out to him. :doh: “And because scientists are first and foremost human beings, they’re loathe to change their theories or their minds because of mere data.” - Glen Hodges
Our Forgotten Astronomy | Object Oriented Programming with C++
