Question

Find the power needed to lift 25 lb. a distance of 15 feet in 20 seconds.

A. 18.75 foot-pounds per second


B. 8 foot-pounds per second


C. 12 foot-pounds per second


D. 33.3 foot-pounds per second

Answer 1

18.75 ft·lb/s

Explanation:

The units of power tell you how to do the calculation. Put the numbers together in a way that makes the units be units of power:

(15 ft)·(25 lb)/(20 s) = (15·25/20) ft·lb/s = 18.75 ft·lb/s

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This is the beautiful thing about physics. The units have to work out, or you did it wrong.