Question

A water pump lifts water from 10 m below the ground. Water is pumped at a rate of 30 kg/minute with negligible velocity. Calculate the minimum horsepower that the engine should have to do this.

Answer 1

Given:
Height through which water is lifted, h = 10 m
$$\begin{gathered} \mathrm{Flow}\mathrm{rate}\mathrm{of}\mathrm{water}=\left(\frac{m}{t}\right) \\ =30\mathrm{kg}/\min =0.5\mathrm{kg}/s \end{gathered}$$

Power delivered by the engine,
$$\begin{gathered} P=\frac{mgh}{t} \\ =\left(0.5\right)\times 9.8\times 10 \\ =49\mathrm{W} \end{gathered}$$

1 hp = 746 w

So, the minimum horse power (hp) that the engine should possess
$$\begin{gathered} =\frac{p}{746}=\left(\frac{49}{746}\right) \\ =6.6\times {10}^{-2}\mathrm{hp} \end{gathered}$$