A boy of mass 40 kg runs up a flight of stairs 3 m high in 6 s. What is his power? (g = 10 N/kg)
Answer and explanation
Correct answer: A. 200 W
- Step 1: Work done = mgh = 40 x 10 x 3 = 1200 J. Step 2. Power = work / time = 1200 / 6 = 200 W. Answer: 200 W. Why not the others: 1200 W: That is the work done in joules, not the power. 120 W: That multiplies the mass by the height only. 20 W: That divides mass times height by 6 and leaves out g.
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