Question

A man whose mass is 75 kg walks up 10 steps, each 20 cm high, in 5 s. Find the power he develops. Take g = 10 ms^–2.

Answer 1

Step 1: Given data

Mass is, $m=75kg$

Height is, $h=10\times 20cm=200cm=2m$

Acceleration due to gravitation is, $g=10m/s^2$

Time taken is, $t=5s$

Step 2: Calculating work done

When a body of mass $m$ is lifted to a height $h$, work done is given as,

$W=mgh$

Substituting the known values, we get,

$$\begin{gathered} W=75kg\times 10m/s^2\times 2m \\ W=1500J \end{gathered}$$

Step 3: Calculating power

Power is given as,

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

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

Substituting the known values, we get,

$$\begin{gathered} P=\frac{1500J}{5s} \\ P=300W \end{gathered}$$

Therefore, the power developed is $300W$.