Physicshard · Past Paper
A pump can lift 100 kg of water to a height of 100 m in 10 s. If efficiency is 50%, what is the input power?
A10 kW
B20 kW
C5 kW
D40 kW
✓ Correct Answer: B — 20 kW
Output Power = mgh/t = (100*10*100)/10 = 10,000 W. Input = Output/Eff = 10,000 / 0.5 = 20,000 W = 20 kW.
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