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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 | ||
| 410042 | 2005-12-05 03:39:00 | Someone draw a diagram, or finger paint something. The lack of smarts in this thread is truly painful. |
ninja (1671) | ||
| 410043 | 2005-12-05 03:54:00 | And another point ... there appear to be some people who think that the plane is still sitting at the start of the conveyor belt when it takes off. It's not. It will have moved relative to the start of the conveyor. That's a fixed point on the earth. By the time it takes off it will have moved the normal distance it needs to reach takeoff speed, given the acceleration it gets from the thrust. The thrust is not infinite. If it was, the plane wpould fly. To bits. (The question , to avoid being completely stupid, does provide the full runway length.) |
Graham L (2) | ||
| 410044 | 2005-12-05 04:03:00 | Someone draw a diagram, or finger paint something . The lack of smarts in this thread is truly painful . Well then, show us how smart you are ninja . You explain it . I await your incredibly intelligent, concise and compelling arguments with bated breath . Don't spare the jiggahurtz Cheers Billy 8-{) |
Billy T (70) | ||
| 410045 | 2005-12-05 04:07:00 | Glad to see someone agree with me :) Glad to see Jack, that you now agree the plane can take off regardless of what the conveyer belt does. As I said right back at the start it is a no-brainer, and the only difference to a normal take off will be the rotational speed of the wheels. |
Terry Porritt (14) | ||
| 410046 | 2005-12-05 04:17:00 | And another point . . . there appear to be some people who think that the plane is still sitting at the start of the conveyor belt when it takes off . It's not . It will have moved relative to the start of the conveyor . That's a fixed point on the earth . By the time it takes off it will have moved the normal distance it needs to reach takeoff speed, given the acceleration it gets from the thrust . But Graham, if the plane is touching the runway, to move forward its wheels have to have a higher speed than the opposing runway/conveyor . Which is impossible because the question requires us to deal with a wheel/conveyor function which approximates to zero . Neutral . The wheel speed is exactly opposed at all times by the belt . |
Winston001 (3612) | ||
| 410047 | 2005-12-05 04:42:00 | Well, the "opinions" score so far is: 32 yes, it will fly. 36 no, it won't fly. 8 Neutral 6 Pointless (7 if you count this one). On this basis Richard Pearce was probably high on something, and the Wright brothers were levitating. Clearly PF1 is not the home of many budding aeronauts. Cheers Billy 8-{) :D |
Billy T (70) | ||
| 410048 | 2005-12-05 04:44:00 | But Graham, if the plane is touching the runway, to move forward its wheels have to have a higher speed than the opposing runway/conveyor. Which is impossible because the question requires us to deal with a wheel/conveyor function which approximates to zero. Neutral. The wheel speed is exactly opposed at all times by the belt. Oh dear Winston, I'd stick to the law :) The wheels, if allowed to turn freely, can be doing anything, backwards rotation, forwards rotation or zero rotation, just depending on what speed and direction the conveyer belt goes. As Graham said if the tyre/runway friction was zero, they needn't turn at all, or instead of wheels use skis like planes that take off and land on snow. I thought we had at long last settled that point :confused: :stare: |
Terry Porritt (14) | ||
| 410049 | 2005-12-05 04:54:00 | 9 pages...sheesh, it's pretty simple. Why does this question confuse so many people? | pine-o-cleen (2955) | ||
| 410050 | 2005-12-05 05:02:00 | 9 pages...sheesh, it's pretty simple. Why does this question confuse so many people? heh it isn't much better in aviation and physics forums... People get "fixated" on the wheels. :p |
gibler (49) | ||
| 410051 | 2005-12-05 05:03:00 | 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. Ok, start from the beginning. The engines start. They start spinning. When they get to the appropriate speed, they draw enough air through them to pull themselves slightly forwards. The engines have just moved forward with respect to a fixed point (on the ground). This causes the wings to move forward, and the body of the aircraft. It all makes sense up to this point. The wheel struts move forward slightly, as do the wheel axles. This forward motion causes the wheels to spin. The engines of the plane are still moving forward. As the wheels start to spin, the conveyor belt starts spinning the other way. The wheels start sliding at this point, as the thrust force is still pushing the axles forwards, but the wheels wont spin fast enough to convert the translational velocity into the same rotational velocity, as it is cancelled out by the rotation under them from the coneyor belt. This continues to happen, until the plane takes off. It is roughly the same effect as taking off with the wheels locked up. /me hopes it makes sense. |
roddy_boy (4115) | ||
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