Question

A woman pulls a bucket of water of total mass 5 kg from a well which is 10 m deep in 10 s. Calculate the power used by her.

Answer 1

Step 1: Given data

Total mass is, $m=5kg$

The depth (height) of the well is, $h=10m$

Time taken to pull the bucket is, $t=10s$

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 in the above equation, we get,

$$\begin{gathered} W=5kg\times 10m/s^2\times 10m \\ W=500J \end{gathered}$$

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 in the above equation, we get,

$$\begin{gathered} P=\frac{500J}{10s} \\ P=50W \end{gathered}$$

Therefore, power used is $50W$.