Couples

A couple is a pair of equal forces acting in opposite directions. If a couple acts on an object it rotates in position. The moment of a couple is called the torque.

The torque is calculated as: torque = force x perpendicular distance

between forces

In the diagram to the right we need to calculate the perpendicular distance, s cosθ.

So in this case:

Torque is measured in Newton metres, Nm