Question

A water pump driven by petrol raises water at a rate of 0.5$m^3$ minute from a depth of 30$m$ . If the pump is $70$ efficient. the power developed by the engine is:

• A. $1750W$
• B. $2450W$
• C. $3509W$
• D. None of these
  

Answer 1

Answer: (C)

$3509W$

$\begin{array}{c}\text{mass of water drawn per second}\\ \text{will}\frac{0.5\times 1}{60}=\frac{1}{120}kg\\ \text{power needed to draw}\\ mgh=\frac{1}{120}\times 100\times 30\\ =25\text{joule}\end{array}$

$\begin{array}{c}\text{as per question, let power of pump}W\\ \therefore W\times \frac{70}{100}=25\\ \text{of}W=\frac{2500}{70}\\ \text{or}W=35.7\end{array}$

Ans. D