Work and Energy
Work $W = \vec{F}\cdot\vec{\Delta r} = F \> \Delta r \> \cos \alpha$
Work is a scalar, $[W] = 1\,\mbox{N} \times 1\,\mbox{m} = 1\,\mbox{Joule}$
Conservative forces: $W_{\rm c.f.}$ does not depend on path,
only on endpoints
\[
W_{\rm c.f.}(\vec{r} \rightarrow \vec{r}\,') = - \left[ U(\vec{r}\,') -
U(\vec{r}) \right] = - \Delta U(\vec{r})
\]
Potential energy $U_F$ associated with force $F$
\[
\begin{eqnarray*}
F_{\rm gravity}=-mg \quad & \rightarrow & \quad U_g=mgy \\
F_{\rm elastic}=-kx \quad & \rightarrow & \quad U_e={1\over2}kx^2
\end{eqnarray*}
\]
Kinetic energy of translation with velocity $\vec{V}$
\[
K_{\rm tr} = {1\over2}\>{mV^2}
\]
Kinetic energy of rotation with angular velocity $\omega$
\[
K_{\rm rot} = {1\over2}\>{I\omega^2}
\]
Conservation of total mechanical energy
\[
\Delta \left( U + K_{\rm tr} + K_{\rm rot} \right) = W_{\rm non-c.f.}
\]
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