Question

A man whose mass is 50 kg climbs up 30 steps of the stairs in 30 seconds. If each step is 20 cm high, calculate the power used in climbing the stairs.

Answer 1

Step 1: Given data

Mass of man is, $m=50kg$

Height to which the man climbs is, $h=30\times 20cm=600cm=6m$

Time taken is, $t=30s$

Step 2: Calculating work done

Work done is given as,

$W=mgh$

where, $m$ is mass, $g$ is acceleration due to gravity and $h$ is height.

Assume $g=10m/s^2$

Substituting the known values, we get,

$$\begin{gathered} W=50kg\times 10m/s^2\times 6m \\ W=3000J \end{gathered}$$

Step 3: Calculating power

Power is given as,

$P=\frac{W}{t}$

where, $W$ is work done and $t$ is time.

Substituting the known values, we get,

$$\begin{gathered} P=\frac{3000J}{30s} \\ P=100W \end{gathered}$$

Therefore, the power used in climbing the stairs is $100W$.