Question

A pump is required to lift 800 kg of water per minute from a 10 m deep well and eject it with speed of 20 m/s. The required power in watts of the pump will be

• A. 6000
• B. 4000
• C. 5000
• D. 8000

Answer 1

Answer: (B)

4000

Total work done is the sum of potential and kinetic energies,
i.e. $W=mgh+\frac{1}{2}m{v}^2$
Thus,
$P=\frac{W}{t}=\frac{mgh+\frac{1}{2}m{v}^2}{t}$
$=\frac{(800\times 10\times 10)+\frac{1}{2}\times 800\times (20{)}^2}{60}$
$=4000W$.