Question

A man of mass 70kg climbed up a stair case of height 10m in 20seconds. Calculate it's power. (g=10m/s²)

Answer 1

The power is equal to the force times speed:

$$P = Fv$$

The force the man acts is equal to his weigth (assuming it moves with the constant speed):

$$F = mg = 70kg\cdot 10m/s^2 = 700N$$

where $m = 70kg$.

By definition, the speed is:

$$v=\dfrac{10m}{20s} = 0.5m/s$$

Thus, obtain:

$$P = 700N\cdot 0.5m/s = 350W$$

ANswer. 350W.