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Conservation Laws
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The Conservation of Mechanical
NonConservative Forces and the WorkEnergy Theorem
Idea:
If there are
nonconservative forces
then mechanical energy is not conserved. We write,
W
=
W
_{nc}
+
W
_{c}
=
KE
_{f}

KE
_{i}
(7)
where
W
_{c}
is the work done by conservative forces and
W
_{nc}
is the work done by nonconservative forces. Since
W
_{c}
=
PE
_{i}

PE
_{f}
we have,
W
_{nc}
= (
KE
_{f}

KE
_{i}
) + (
PE
_{f}

PE
_{i}
).
(8)
The work done by nonconservative forces is equal to the change in mechanical energy.
wwwadmin@theory.uwinnipeg.ca
10/9/1997