You guess right! Glad to have you on our side 100%. For a while I think you were 75/25.
Any 'plane does not take off' believers care to place a bet with me?
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Will the plane take off?
- Thread starter poet_x
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You guess right! Glad to have you on our side 100%. For a while I think you were 75/25.
Any 'plane does not take off' believers care to place a bet with me?
If you are actually going to build a huge treadmill and run a plane down it, I got some cash in it just for entertainment value. Xpo side show? I'll bring the beer.
Wow, this has been answered before: to come up with a definitive answer, you have to make an assumption.
1. You assume the plane is stationary relative to the ground/surrounding air molecules--ignoring minor air flow:
2. The plane moves forward relative to the ground/surrounding air:
Depending on how far and fast you move, you can achieve lift and take off.
However, the whole point of the set up was to imply that the plane remains stationary to the ground/surrounding air. So the correct answer would be it does not take off.
I am absolutely certain these scenarios are exhaustive and exclusive.
This was absolutely NOT the point of the question. The point was for YOU to figure out if given the scenario, would the plane move or not. It was not telling you the plane was stationary, it was not telling you it would move. It's up to you to SOLVE that given the data. THAT was the entire point of the question and once you solve that, THEN you have the answer. Way too many have jumped to the conclusion that if the treadmill speed matched the plane speed, then it would be stationary. That is not an assumption, that's an incorrect answer to the question.
Then what happened to the energy output by the engines? Conservation of energy isn't just a good idea, it's the law.
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I'm pretty sure my last post sums it up. You either believe the plane moves or the plane doesn't--relative to the ground. There are no other options. The list is exclusive and exhaustive.
If the plane doesn't move relative to the ground, it won't take off. Argue whatever you want--you are going to be wrong.
If you believe it moves, fine. Then it takes off if it reaches a certain speed/distance just like any other normal takeoff. Why bother with the question and the elaborate--yet vague--set up? There is no point to the treadmill if you are going to let the plane move forward any distance relative to the ground. You may as well say something like: you cut the engines to X% of the normal output used in a nominal takeoff; you cut the distance allowed for takeoff by X%.
The problem is that you are thinking about distance displaced by the plane relative to the runway it is on. Normally, this is the ground. In the question, it is the belt of the treadmill. You need to be thinking about the plane relative to the surrounding air. Once you understand how we are able to fly, the solution becomes obvious. Again, we are talking about a normal passenger airplane--not a harrier or some kind of jet with thrust vectoring.
You could put wings on a treadmill, and if you passed enough air over and under the wings the treadmill will takeoff. That'd be a funner scenario. Or an NSX. That'd be better.
If the plane doesn't move relative to the ground, it won't take off. Argue whatever you want--you are going to be wrong.
If you believe it moves, fine. Then it takes off if it reaches a certain speed/distance just like any other normal takeoff. Why bother with the question and the elaborate--yet vague--set up? There is no point to the treadmill if you are going to let the plane move forward any distance relative to the ground. You may as well say something like: you cut the engines to X% of the normal output used in a nominal takeoff; you cut the distance allowed for takeoff by X%.
The problem is that you are thinking about distance displaced by the plane relative to the runway it is on. Normally, this is the ground. In the question, it is the belt of the treadmill. You need to be thinking about the plane relative to the surrounding air. Once you understand how we are able to fly, the solution becomes obvious. Again, we are talking about a normal passenger airplane--not a harrier or some kind of jet with thrust vectoring.
You could put wings on a treadmill, and if you passed enough air over and under the wings the treadmill will takeoff. That'd be a funner scenario. Or an NSX. That'd be better.
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Good God!
"A plane is standing on a runway that can move (some sort of band conveyer). The plane moves(it moves people, IT MOVES! It is not being held in place!) in one direction, while the conveyer moves in the opposite direction. This conveyer has a control system that tracks the plane speed (the plane has forward movement and speed!) and tunes the speed of the conveyer to be exactly the same (but in the opposite direction). Can the plane take off?"
"A plane is standing on a runway that can move (some sort of band conveyer). The plane moves(it moves people, IT MOVES! It is not being held in place!) in one direction, while the conveyer moves in the opposite direction. This conveyer has a control system that tracks the plane speed (the plane has forward movement and speed!) and tunes the speed of the conveyer to be exactly the same (but in the opposite direction). Can the plane take off?"
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That is just poor wording to say that the plane is facing one direction and the conveyer belt is moving in the opposite direction relative to the direction the plane is facing. If the plane is able to move, there is no point to the conveyer belt and there is no solution without more information. Again, all you need to consider is how fast and how far the plane moves relative to the air surrounding its wings. That's it. Take away the treadmill if it helps.
Since this is a car forum, a better set-up would be as follows:
You have a Honda F1 car on frictionless dyno rollers (I don't know the precise terminology, but I think you get the point). You load the engine to where, if not on rollers, the car would be traveling 170 mph. Do you experience any downforce or any lift? Or if you sat in the car, would you feel any wind blowing in your face? :biggrin:
The answer is no. On frictionless rollers, you could take off all the aerodynamic wings/splitters and the car wouldn't go tumbling into the air. Why? The air is relatively static (ignoring minor fluctuations) around the car.
Hope that helps some of you visualize the problem.:biggrin:
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You might want to re-think this question. The engines are operating nominally--combustion is nominal, output is nominal. I don't understand why you would think there is a problem with conservation of energy. Explain why you think this law is being violated and I think you'll find the solution to your own question.
The question is worded perfectly and intentionally, there is no ambiguity and there are no assumptions other than we're dealing with a conventional airplane and not a VTOL. The entire object of this puzzle is to figure out if by spinning the treadmill at the same speed the plane is moving, will it hold the plane stationary or will the plane move forward, this is why you're not explicitly told one or the other, THAT is the real puzzle here. By answering that question, you'll be able to answer the whole puzzle, will it fly or not.
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Perfectly worded? :biggrin:
Whatever you say. I can't convince those who don't want to be, but let me ask you a few questions:
1. What is speed? What is velocity?
2. What is the speed and/or velocity relative to in this situation?
I.e. Give me a hypothetical speed for the plane and a hypothetical speed for the treadmill and describe the planes movement relative to the ground and the treadmill.
Don't take too long--it's rhetorical.
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Again, this should help visualize the problem. If any of you still feel the need to be convinced, take your car to get dyno'd. Let me know how much wind burn you get from loading the engine up.
Or if you still concede that the plane moves forward relative to the ground--that is fine by me. That's certainly a valid assumption to be made. So it moves forward--how is this a difficult question and how do you know if you can take off without knowing at what speed the plane is traveling relative to the ground, how heavy the plane is how far the plane travels etc? Those parameters aren't given because that wasn't the point of the poorly-worded question and if they were it seems like it would be just like any other takeoff.
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Since I am subscribed to this mess of a thread I want to remind the non scientists that the ground we walk on ,the treadmill, the plane, all are moving relative to what? You of course have to figure in the rotation of the earth and the massive speed our galaxy is moving away from the center of the universe.....there I just finished my last spleef.:redface:
No, it doesn't. It won't move, and be stationary, if you use the ground as the reference point, which is needed to give the plane much needed "lift" to be able to take off.
Ummm, on the second thought, I don't think the plane will take off because the engine will get overheated, and explode.
See you already have a PLANE ON A TREADMILL...SO............The engine can't blow up. We are already in fairytale land where big huge airplanes can be on gaint oversized treadmills.
Does anyone think sears will take back a few treadmills and some RC planes used for one day?
Only if you can prove them that the plane took off. :biggrin:
I'd do it. I am not a pilot nor have I got any skills to fly an airplane. But who gives a damn. :tongue:
They have giant fans, and that will give you enough lift on the dyno. Plus, Cars on dynos don't have wings. Your assumption isn't valid.
Go back and study your basic physics.
I will rent the plane and get a treadmill. I think if we put you up in a Hoilday Inn Express the night before we should be A.O.K.:wink:
It conserves. The thread mill doesnt run on free will.
Rent a plane with NOS button, just to be safe, if it doesn't take off, I will use it!
