Quote:
Originally Posted by Man Overboard  2kmg weight is not stated (kg/2). Friction is not stated, and therefore can not be assumed. We can assume that the weight is located in the center of the plate that ties pulleys 3 and 4 together because of the kg/2 vector for both pulleys 3 & 4. Duration through "x" degrees is also not stated, but rather a cause and effect statement is made, and it is valid regardless of duration. Even if there is no obvious purpose, it is good to exercise ones understanding of physics. |
It is indeed good to exercise one's understanding of physics.
For instance, the whatever-it-is in post 1. If it is symmetrical, it doesn't do jack. If it's not symmetrical, the top part falls down. The steady state solution in both cases is that it sits there and does nothing. The only difference is that in the second case, there is a transient term in the solution which disappears once the device comes to rest. No more energy can come out of it, than the difference in potential energy between the state it's drawn in and the state where it is done collapsing under its own weight. Which is pretty small; if the thing's a half-metre high overall and the upper part weighs 10 kg, you're talking maybe 50 joules, tops. Bottom line, if you believe that it's good for anything, go dig out your grade 10 physics book because I assure you, it's pretty darn useless.
12-01-2006, 04:12 PM
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