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| Thread ID: 93430 | 2008-09-16 06:00:00 | Aircraft Taking off problem | Thomas01 (317) | PC World Chat |
| Post ID | Timestamp | Content | User | ||
| 705629 | 2008-09-16 21:56:00 | As I see he often makes statements with nothing to actually back them up. Unfortunately Mother Nature forgot to connect his mouth to his brain and so it flops about unaided.:groan: |
Roscoe (6288) | ||
| 705630 | 2008-09-16 22:04:00 | Hmmm. Part 2. And Billy, please re-read the original question, then explain to me how the plane could possibly be moving forward when the wheels and the conveyor are moving at the same speed in opposite directions. To do so violates the standard rules of physics. | Erayd (23) | ||
| 705631 | 2008-09-16 22:41:00 | Unfortunately Mother Nature forgot to connect his mouth to his brain and so it flops about unaided.:groan: Lmao. God damn that made me laugh. |
Metla (12) | ||
| 705632 | 2008-09-17 01:14:00 | Would Roddy explain why he thought last nights demo was so flawed? As I see he often makes statements with nothing to actually back them up. See here: LOL WUT. If the conveyor speed matches the wheel rotational speed exactly, as you have said, then why have you used different numbers in your example? You've made the conveyor match the airspeed rather than the wheel rotational speed. The conveyor should be going backwards at 160 knots, not 80. However, this causes the wheels to be spinning faster, meaning the conveyor should be going faster. And so on. You're wrong, *****. In the experiment, they were unable to replicate the magic conveyor belt that always matches the wheels' rotational speed. Instead, it matched the air speed of the plane, in which case, of course it will fly. Lets say we put a runway on the equator facing east west. The earth is spinning at the equator at about 6,000 mph from east to west. We put a plane on the western end of the runway facing east, now well the plane take off. This is the same as putting a plane on a conveyor belt. You all know the answer to this. :) Well it? I don't know if it well. It could very well fly. Maybe it well not fly if the pilot is unwell. Hmmm. Part 2. And Billy, please re-read the original question, then explain to me how the plane could possibly be moving forward when the wheels and the conveyor are moving at the same speed in opposite directions. To do so violates the standard rules of physics. I think we're **** out of luck here, Billy strikes me as one of those people who has never been wrong in his life. |
roddy_boy (4115) | ||
| 705633 | 2008-09-17 02:13:00 | Unfortunately Mother Nature forgot to connect his mouth to his brain and so it flops about unaided.:groan: :banana :clap :punk |
Trev (427) | ||
| 705634 | 2008-09-17 02:59:00 | I may as well have another :2cents: worth and propose a scenario that will allow the plane to fly whilst generally conforming to the conditions of the question....... but first...... The original question is so badly worded, unscientific and unmathematical that it is no wonder that there has been so much disagreement. It was not until around post 49 J_Joyce, and then posts 186 Jack Straw and 187 Erayd/Bletch of the original plane thread that the impossibility of satisfying the conditions of the question were raised (according to how the question is interpreted) Prior to that there was a lot of bogging down with ideas of tractive effort at the wheels. Most people by now, except Billy :) seem to accept that the wheels will have to "move faster" than the conveyor when the plane moves forward to get up airspeed. BUT that is not allowed by the terms of the question, or at least as the question can be interpreted. Here is the scenario to achieve the seeming impossible: :) We have to propose the sort of silly assumptions that plague or used to plague high school applied maths questions: 1.Suppose the conveyor is made of light inextensible flexible material, ie it is weightless and can't stretch but can bend without effort.. 2. Let the conveyor run on frictionless bearings, and have no air drag on it. 3.Let there be rolling tyre friction between the wheels and the conveyor. With these assumptions when the plane begins to move forward due to engine thrust, the wheels will DRIVE the conveyor. As the plane moves faster, the wheels will drive the conveyor faster, and in a direction opposite to the direction of travel of the wheel axles, and at the same linear speed as the surface speed of the tyre......thus satisfying the terms of one interpretation of the question Original question for reference: "Imagine a plane is sat on the beginning of a massive conveyor belt/travelator type arrangement, as wide and as long as a runway, and intends to take off. The conveyer belt is designed to exactly match the speed of the wheels at any given time, moving in the opposite direction of rotation. There is no wind. Can the plane take off?" |
Terry Porritt (14) | ||
| 705635 | 2008-09-17 04:24:00 | I think we're **** out of luck here, Billy strikes me as one of those people who has never been wrong in his life. But his wife has been many times |
plod (107) | ||
| 705636 | 2008-09-17 07:43:00 | I don't think you have to make silly assumptions, Terry . The speed of a freely rotating wheel's line of contact with the ground relative to the ground is zero . It's not skidding . The only meaning which can be given to the "speed" of the wheel is the linear speed of the axle relative to the ground; the speed of the plane over the ground . Put the expensive "conveyor" between the ground and the wheel . As the plane accelerates, the surface of the conveyor matches the linear speed of the axle, but backwards . The wheel spins because its line of contact with the conveyor is stationary relative to the conveyor . But the axle continues to move forwards relative to the ground, because the plane is being impelled by the thrust of its engine . Whatever the conveyor does has no effect on that . The wheel shouldn't burst, because it will just rotate at the normal rpm for the plane's speed over the ground, just backwards, so it will continue to perform its function of keeping the plane from rubbing on the ground/conveyor . The plane will take off . It's a silly question . |
Graham L (2) | ||
| 705637 | 2008-09-17 07:56:00 | Right Graham, or, as in the words of Professor Joad of the Brains Trust, "It all depends on what you mean by wheel speed" | Terry Porritt (14) | ||
| 705638 | 2008-09-17 08:24:00 | Ok forgive me for being blonde here but... This is how I see it: Ok, from what I remember in physics is Newtons law? "every action has an opposite and equal reaction" Therefore, if the wheels on the plane are moving forward at a speed of 80 mph, and the conveyor belt is moving in an opposite direction of 80 mph, essentially the plane is not moving forward (both forces cancel each other out). So where does air speed fit in if the plane is not actually moving forward? From what Im reading, it sounds like some are saying the conveyor belt is moving at 80 mph, so therefore the wheels have to travel at 160 mph to obtain an actual speed of 80 mph :confused: |
Myth (110) | ||
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