Question

Calculate the power of an electric pump in horse power, which can lift 2000 m³ of water from a depth of 20 m in 25 minutes.

[Take g = 10 ms⁻², 1 m³ of water = 10³ kg and 1 HP = 750 W]

Answer 1

Mass of water = 2000 × 10³ = 2,000,000 kg

Work done in lifting the water = mgh

= 2,000,000 × 10 × 20

= 400,000,000 J

Time = 25 × 60 = 1,500 s

\[ \text{Power} = \frac{\text{Work}}{\text{Time}} \]

\[= \frac{400{,}000{,}000}{1{,}500} \]

= 266,666.7 W

Power in HP = \[ \frac{266{,}666.7}{750} \]

= 355.56 HP