Question 13
Work, Energy and PowerAn electric water pump rated 1.5 kW, lifts 200 kg of water through a vertical height of 6 metres in 10 seconds. What is the efficiency of the pump? [g = 10 m s−2, neglect air resistance]
- A.90.0%
- B.85.0%
- C.80.0%
- D.65.0%
Show the answer and explanation
Answer: C (80.0%)
Explanation
Useful power = mgh/t = 200 × 10 × 6 ÷ 10 = 1200 W. Efficiency = 1200/1500 × 100% = 80%.