Question

A man raises a box of mass 50kg to a height of 2m in 20s, while another man raises the same box to the same height in 50s. (a) Compare: (i) the work done, (ii) the power developed by them. (b) Calculate the (i) the work done, (ii) the power developed by each man. Take g = 10N kg^-1.

April 17, 2024

Answer

(a) (i) Work done = force x displacement

Hence, work done is same for both men as both carry 50 kg weight to a height of 2m.

Therefore,

Work done by first man : Work done by second man = 1 : 1

(ii) Let the work done by both men be W.

Power = $work\over time$

Power developed by Man A : Power developed by Man B = $W\over 20$ : $W\over 50$

= $5\over 2$

Power developed by Man A : Power developed by Man B = 5:2

(b)

(i) As we know,

W = F × S = mgh

W = 50 × 10 × 2 = 1000 J

(ii) Power developed by Man A (P_A) = $1000\over 20$

= 50 W

Power developed by Man B (P_B) = $1000\over 50$

= 20 W

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