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Question
A man raises a box of mass 50 kg to a height of 2 m in 20 s, while another man raises the same box to the same height in 50 s. Compare:
- the work done, and
- the power developed by them. Take g = 10 N kg-1
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Solution
Mass of box m = 50 kg
Height to which box is raised h = 2m
(i) Work done by each man = mgh
= 50 × 10 × 2
= 1000 J
∵ Work done is independent of time taken
∴ Ratio of work done = 1 : 1
(ii) `"Power in first case"/"Power in second case" = (w/t_1)/(w/t_2)`
= `(1000/(20 s))/(1000/(50 s))`
= `50/20`
= 5 : 2
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