Work is force multiplied by distance and has units of

J = joule = N-m

Work is the component of the force in the direction of the displacement, multiplied by the displacement,


Energy is the ability to do work. You may think of energy as "stored up work";

KE = (1/2) m v2

PEg = m g h

PEel = (1/2) k x2

We encounter many situations or many systems for which the total energy remains constant. We describe this by saying Energy is conserved.

E = PE + KE

E = constant

PE + KE = constant

Ei = Ef

PE i + KE i = PE f + KE f

More Examples

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(c) 2002, Doug Davis; all rights reserved