WEBVTT

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Here is the problem: A motor does 72000 J of work in 3600 s. What is its power?

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Use the power formula, rearranged for the unknown, in SI units.

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Formula: power.

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Substitute the known values.

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So the answer is power P equals 20 W.

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Power is the rate of doing work: one watt is one joule per second. The same work done in half the time needs twice the power.

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Substituted every value back into the formula: both sides agree, which checks out.