\begin{definition}[Definition:Line of Action]
Let a force $\mathbf F$ act on a rigid body $B$.
In order to completely specify how $\mathbf F$ acts on $B$, it is necessary to know the point $P$ on $B$ at which $\mathbf F$ is applied.
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The (straight) line $L$ passing through $P$ in the direction of $\mathbf F$ is known as the '''line of action of $\mathbf F$ on $B$'''.
\end{definition}