The amount of work (W) done in a moving object can be found by using the following equation:

Work = force X distance or W = Fd

Work is expressed in units called joules (J). One joule is equal to the energy expended (or work done) when a force of one newton is applied to an object, and the object is moved a distance of one meter. So, one J is the same as 1 N • m.

Let's try some practice problems.

Practice Problem 1

A crane lifts a load of logs 3 meters with a force of 5,200 Newtons. How much work did the crane do?

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Check your Answer

W = Fd
F = 5,200 N • 3 m
F = 15,600 N • m or 15,600 J

Practice Problem 2

Jake uses 45 Newtons of force to move the cart 6.5 meters. How much work did Jake do?

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Check your Answer

W = Fd
F = 45 N • 6.5 m
F = 292.5 N • m or 292.5 J

Practice Problem 3

Andy uses a force of 20 Newtons to push a lawn mower 20 meters. How much work did he do?

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Check your Answer

W = Fd
F = 20 N • 20 m
F = 400 N • m or 400 J

Challenge Question

A 45 kg girl sits on an 8 kg bench. How much work is done on the bench?

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Check your Answer

W = Fd
F = 45 N • 0 m
F = 0 N • m or 0 J
No work is done in this example because the bench did not move.