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# A weightlifter lifts a 120 kg weight over his head.

A weightlifter lifts a 120 kg weight over his head. Assume that the weight is initially at rest on the ground, and after the lift it is held at rest above the weightlifter's head, a vertical distance of 2.5 m above the ground. (a) compute the work done by the weightlifter on the weight. (b) Now the weightlifter lowers the weight very slowly onto the ground and gently places it at rest on the ground. What is the work done by the weightlifter on the weight during the lowering of the weight? Does the weightlifter do any net work during the combined process or lifting then lowering the weight? If not, why is the weightlifter tired? (c) Suppose that instead of lowering the weight gently, the weightlifter drops it from above his head. Is the total work done by the weightlifter in this case larger or smaller than if he had lowered it gently? Explain.

a) W = 2940 J b) W = -2940 J c) Work done... View the full answer

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