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:

1. the work done, and
2. the power developed by them. Take g = 10 N kg^-1

Answer 1

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