Question

A man rises a box of mass 50 kg to a height of 2 metre in 2 minutes , while another man rises the same box of the same height in 5 minutes. Calculate the work done by each man. Also compare: (i) the work done(ii) the power developed by them. ( g=10 N kg^-1)

Answer 1

work = force × distance

for the 1st man,

work done = (50×10) × 2 =1000 jule .
power developed,
= (work done) / (time taken by the 1st man)
= 1000 / (2×60)

=8.333 watt.

for second man,

work done = (50×10) × 2 = 1000 jule.
power developed,
= (work done) / (time taken by 2nd man)
= 1000 / (5×60)
= 3.33 watt.

Comparison :
here,
(1) W.D by 1st man / W.D by 2nd man
= 1000/1000
= 1

(2) Power devloped by 1st man / Power devloped by 2nd man
={1000/(2×60)} / {1000/(5×60)}
={1000/(2×60)} × {(5×60)/1000}
={5/2}
=2.5

hence the conclusion is that work is done by both the man is same however the power developed by 1st man is 2.5 times greater than 2nd man.

because they have done the same amount of work in different different times, who has taken less time they have more power and who has taken more time they have less power.

I hope this will helps you......