Lesson: Chapter 18 — Work, Energy and Power

18.3. Power 4 of 7 Reset answers

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Question 4

An object of mass 5 kg is raised to a height of 8 m in 10 seconds. What is the power? (g = 10 m s^-2)

A 400 W B 4000 W C 4 W D 40 W

The right answer is the one marked above.

40 W. weight = 50 N, so work = 50 N × 8 m = 400 J. power = 400 J ÷ 10 s = 40 W.

400 W is the work, not the power — it is what you get by forgetting to divide by the time at the end.

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