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russ_watters is online now
Oct15-09, 05:09 PM
P: 21,998
First istellyl is right that the fan energy is not conserved - this is obvious enough given that it expends energy whether the ball is there or not. Second, this "instantaneous force" adds another input. No violations here, just a problem you haven't diagrammed out. It would help you understand better if you wrote a mathematical conservation of energy statement.