# Moments

The moment (or torque) of a force about a turning point is the force multiplied by the perpendicular distance to the force from the turning point.

Moments are measured in newton metres (Nm).

## Moment = F d

• F = the force in newtons (N)
• d = perpendicular distance in metres (m)

Example; A 10N force acts at a perpendicular distance of 0.50m from the turning point. What is the moment of the force? Moment = Fd
= 10 x 0.50
= 5.0 Nm

### The principle of moments.

” When an object is in equilibrium the sum of the anticlockwise moments about a turning point must be equal to the sum of the clockwise moments.”

sum of anticlockwise moments = sum clockwise moments

Example; sum of anticlockwise moments = sum clockwise moments
F1 x d1 = F2 x d2

OR sum of anticlockwise moments = sum clockwise moments
F1 x d1 =  (F2 x d2) +  (F3 x d3)

### Couples

A couple is two equal forces which act in opposite directs on an object but not through the same point so they produce a turning effect.

The moment (or torque) of a couple is calculated by multiplying the size of one of the force (F) by the perpendicular distance between the two forces (s).

E.g. a steering wheel in a car; OR 