InterviewSolution
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InterviewSolution
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Four men light a 250 kg box to a height of 1m and hold it without raising or lowering it. (a) How much work is done by the men in lifting the box ? (b) How much work do they do in just holding it ? (c ) why do they get tired while holding it ? `(g = 10m//s^2)` |
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Answer» (a) Mass of the box, m = 250 kg Height through which it is lifted, h = 1 m Work done in lifting the box = increases in the PE = of the box= mgh = (250) (10) (1) = 2500 N (b) When the men just hold the box, s = 0 and as such W = F s = 0 (c ) To hold the box, the men have still to apply a force equal to the weight of the box in the opposite direction To apply this force, men have to exert muscular effort which is the cause of their tiredness. |
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