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Work-energy theorem review

Review the key concepts, equations, and skills for the work-energy theorem.  Understand how the work-energy theorem only applies to the net work, not the work done by a single source.

Key terms

Term (symbol)Meaning
Net work (W, start subscript, start text, n, e, t, end text, end subscript)Work done by the net force on an object. SI units of start text, J, o, u, l, e, s, space, left parenthesis, J, right parenthesis, end text or start text, N, end text, dot, start text, m, end text
Work-energy theoremNet work done on an object equals the object’s change in kinetic energy. Also called the work-energy principle.

Equations

EquationSymbolsMeaning in words
Wnet=KK0=ΔK\begin{aligned}W_{\text {net}} &= K - K_0 \\&= \Delta K\end{aligned}W, start subscript, start text, n, e, t, end text, end subscript is net work, K is final kinetic energy, K, start subscript, 0, end subscript is initial kinetic energy, and delta, K is change in kinetic energyThe net work on an object is equal to the object’s final kinetic energy minus the initial kinetic energy.

Common mistakes and misconceptions

Sometimes people forget that the work-energy theorem only applies to the net work, not the work done by a single force. The work-energy theorem states that the net work done by the forces on an object equals the change in its kinetic energy.

Learn more

For deeper explanations of the work-energy theorem, see our video work and the work-energy principle.
To check your understanding and work toward mastering these concepts, check out calculating change in kinetic energy from a force and velocity and mass from force vs. position graphs.

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