Moment

$$\begin{align*} M &= Fd \\ \text{moment of a force} &= \text{force} \cdot \text{perpendicular distance from pivot} \end{align*}$$

Unit of $M$ = $\mathrm{N\,m}$

If force applied is not perpendicular, either resolve distance or resolve forces

Note

• Moment - distance perpendicular to force
• Work - distance parallel to force

Principle of moments

A system is in rotational equilibrium if

$$\text{sum of clockwise moments} = \text{sum of anticlockwise moments}$$

Centre of gravity

Single point where the whole weight of the object is considered to act at