Question

A boy weighing 40 kg carries a box weighing 20 kg to the top of a building 15 m high in 25 seconds. Calculate the power. (g = 10 m/s²)

Answer 1

Mass of the boy, (m₁) = 40 kg
Mass of the box, (m₂) = 20 kg
Height, (h) = 15 m
Acceleration due to gravity, (g) = 10 m/s² 
Time taken, (t) = 25 s 
Total mass of the system,
M = m₁ + m₂
=> M = 40 + 20 = 60 kg
So, work done by the boy is,
W = mgh
=> W = (60)(10)(15)
=> W = 9000 J
Now, we can calculate the power of the boy as,
Power = `"Work done"/"Time"`
So , 
Power = `9000/25` W
= 360 W

So, the power is 360 W.