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A moment, $\mathbf{M}$, is defined and the product of the force and the perpendicular distance of the force from a pivot. $$\mathbf{M}=Fs$$ where the force, $F$ is perpendicular to the displacement, $s$.

If the force and displacement are not perpendicular then the moment of the force is given by
$$\mathrm{moment}=Fssin\theta $$
where $\theta $ is the angle between the force and the displacement.

Or in vector notation
$$\mathbf{M}=\mathbf{F}.\mathbf{s}$$

For equilibrium both the sum of the forces and the sum of the moments must be zero, i.e., $$\Sigma {F}_{i}=0$$ and $$\Sigma {\mathbf{M}}_{i}=0$$

A Level