Question

A man weighing 50 kg carries a load of 10kg to the top of building in 8min. The work done by the man is 60kJ. If he carries the same load bin 4 min. How much work would he do?

Answer 1

answer : 60kJ

here I will mention misconception and actual concept. let's see.

misconception :

A man weighing 50 kg carries a load of 10kg to top of building in 8min. The workdone by man is 60KJ.

power of man = workdone by man/time taken

= 60kJ/(8 × 60)

= 1/8 kW

now he carries the same load in 4 min

then, workdone by man = power of man × time taken

= 1/8 kW × 4min

= 1/8 kW × 4 × 60 sec

= 30 kJ

actual concept :

workdone by the man = change potential energy = mgh

here it is clear that workdone by the man doesn't depend on time. it depends on height and mass of the body.

so, work done by man is same i.e., 60kJ

Answer 2

$\huge\bold\purple{Answer:-}$

60kJ