A pump raises 200 kg of water through 10 m in 20 s. Taking g as 10 m s-2, its output power is
Correct answer: B. 1000 W
- A. 100 W
- B. 1000 W
- C. 2000 W
- D. 20000 W
Explanation
The work done is mgh, which is 200 times 10 times 10, giving 20000 J. Dividing by the 20 s taken gives 1000 W, or 1 kW. Forgetting to divide by time leaves the answer at 20000, which is the energy in joules rather than the power in watts.
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About Power
Power is the rate at which work is done or energy is transferred, with average power calculated over a time interval and instantaneous power found from P = Fv when force and velocity are aligned. Work includes units, mechanical efficiency, and the distinction between power and total work or energy.
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