Question

Q3.A boy of mass 50 kg climbs 12steps each of height 20 cm in 50 seconds. Calculate the power used by the boy in climbing the stairs.

Answer 1

By definition, the power is the work $A$ divided by time $t=50s$ :

$$P = \dfrac{A}{t}$$

The work done by the boy is:

$$A = mgh$$

where $m = 50kg, g=9.8m/s^2$ and $h = 12\cdot 20cm = 2.4m$ is the total height. Thus, obtain:

$$P = \dfrac{50kg\cdot 9.8m/s^2\cdot 2.4m}{50s} =23.52W$$

Answer. 23.52W.