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| Thread ID: 64128 | 2005-12-04 07:01:00 | Sunday night Brain Bender - Airplane Physics | miknz (3731) | PC World Chat |
| Post ID | Timestamp | Content | User | ||
| 410052 | 2005-12-05 05:15:00 | Winston, on your motorbike you depend on friction for your travelling . As long as there's friction, the wheels don't move on the road . The "point" on the tyre touching the road at any moment is stationary, unless you are skidding . If you are skidding, you just ran out of friction . Since the wheels are rotating, their axles (and the rest of the bike, you hope) are moving relative to the road . To move, you transmit torque to the rear axle, and that rotates the wheel . Since the instantaneous bottom of the wheel is "glued" to the road by friction, the axle moves forwards . If you put the bike on a stand, or put the rear wheel on rollers, you can spin the rear wheel at a great speed without moving . If you put it on a treadmill, and adjust the speed of the belt, you can stay in one place, similarly . On ice, with no friction, you stay still, then fall off . But the motorbike wheel is driven . Sit on your motorbike (with learner wheels or a sidecar so it will stand up) on the ice . Select neutral gear . Connect a tow rope, and get a tow from a car . You'll move . The wheels might or might not turn, becuase there's could be some friction . But you could be towed sideways, without too many problems . Now put it on a treadmill . The tow rope will pull you off it . Whatever the speed of the treadmill . The wheels will turn, because they are stuck to the belt by the friction . But they have nothing to do with causing the motion . That's the situation with the plane . But it doesn't need to have the wheels turning . They just do . |
Graham L (2) | ||
| 410053 | 2005-12-05 05:17:00 | Having now had time to think this through in a logical and not droswy state of mind, i would now conclude that yes the plane would take off. I thought of it like this, if you put a little model plane on a treadmill and held your finger behind it so that it did not move, then began to exert forwards motion upon the aircraft it would move forward despite what the wheels were doing. |
lagbort (5041) | ||
| 410054 | 2005-12-05 05:23:00 | after reading through all the posts I was still stumped and thought no the plane can't fly, so I spoke to a mate who is a pilot and you are right the plane still won't fly given the facts in the question, he gave me a formula for flight which was far to complicated for me to remember but it still said plane won't fly. reasons given that no matter how much thrust from what ever propoltion unit the wheels will keep spinning faster and faster and so will the conyeour belt leaving the plane stationary, and with no wind there is no lift. people seem to be making this a lot more complicated then it really is with there different formulas |
plod (107) | ||
| 410055 | 2005-12-05 05:33:00 | Plod - That is what I thought at first, that the wheels and conveyor belt would just spin to an infinite speed. But then think about the beginning, as I said in my post. What causes the wheels to spin in the first place? The engines moving forward. Causing everything else to too. Once the engines have moved forward that first infinitessimal amount, there is no going back. It has moved forward relative to a fixed point, and will continue to do so. |
roddy_boy (4115) | ||
| 410056 | 2005-12-05 05:40:00 | plod: Does his plane have pedals to work the wheels? . . . reasons given that no matter how much thrust from what ever propoltion unit . . . If you've got thrust you get acceleration . It needs no complicated equation . Newton gave us a simple equation: F=ma . It doesn't matter what the wheels are doing . The plane is going to accelerate along the line of the thrust . Acceleration is the rate of increase of speed . Speed is distance/time . The plane moves . When its speed is high enough, it flies . (Have a look at my previous posting #91, too) . |
Graham L (2) | ||
| 410057 | 2005-12-05 05:42:00 | Plod - That is what I thought at first, that the wheels and conveyor belt would just spin to an infinite speed. But then think about the beginning, as I said in my post. What causes the wheels to spin in the first place? The engines moving forward. Causing everything else to too. Once the engines have moved forward that first infinitessimal amount, there is no going back. It has moved forward relative to a fixed point, and will continue to do so. think of a car on a dyno, it stay still. It doesn't matter if the cars power is driving the wheels or if it is jet powered(as long as thereis no wall behind the car) |
plod (107) | ||
| 410058 | 2005-12-05 05:48:00 | think of a car on a dyno, it stay still. It doesn't matter if the cars power is driving the wheels or if it is jet powered(as long as thereis no wall behind the car) ... if you sat a jet powered car on a dyno without tying it down it would fly off the dyno. the movement of the wheels has no bearing as it is the main body of the car being pushed not the wheels being turned with the movement of the car itself being and added effect |
lagbort (5041) | ||
| 410059 | 2005-12-05 05:49:00 | I think the big problem is people trying to figure out the wheels, as has been said many times. The conveyor belt doesn't exist. It can't. The wheels move forward, no matter what the belt is doing, rendering the idea that it can turn to counteract the spin impossible. | roddy_boy (4115) | ||
| 410060 | 2005-12-05 06:15:00 | I think the big problem is people trying to figure out the wheels, as has been said many times . The conveyor belt doesn't exist . It can't . The wheels move forward, no matter what the belt is doing, rendering the idea that it can turn to counteract the spin impossible . But surely the belt increases speed as quickly as the wheels leaving the plane standing still . This question returned over 18 pages of arguments on another forum I go to!! :badpc: :badpc: :badpc: :badpc: |
miknz (3731) | ||
| 410061 | 2005-12-05 06:20:00 | Plod - That is what I thought at first, that the wheels and conveyor belt would just spin to an infinite speed. But then think about the beginning, as I said in my post. Once the engines have moved forward that first infinitessimal amount, there is no going back. It has moved forward relative to a fixed point, and will continue to do so. Agreed. Thankyou all. That is what I originally thought this morning but reading more posts................sheesh. :groan: |
Winston001 (3612) | ||
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