JEE Main Physics question
An electric pump is used to fill an overhead tank of capacity 9 m³ kept at a height of 10 m above the ground. If the pump takes 5 min to fill the tank by consuming 10 kW power, the efficiency of the pump should be (g = 10 ms⁻²)
Answer: (D)
Solution
Useful work = mgh = (9×1000)(10)(10) = 9×10⁵ J. Useful power = 9×10⁵/(5×60) = 3000 W = 3 kW. Efficiency = 3/10 = 30%.