What Is The Moment Of A Force?

The turning effects of forces are widely utilised in everyday life. When the door is opened, the force on the handle exerts a turning effect about the hinges. It is a common experience that a large force is needed to open the door if the force is applied near the hinges. Thus the turning effect of a force depends on two factors: (a) the magnitude of the force, and (b) the distance of the line of the force from the axis or fulcrum about which turning takes place. The turning effect of a force is called its moment and is defined as follows:

Moment of a force about a point or axis = Force x perpendicular distance of the line of action of the force from the point or axis.

It is obvious that the turning effect of a small force can be increased by applying it at a large distance. Spanners, used for screwing and unscrewing nuts and bolts, work on this principle.

While playing on a see-saw, a weak boy can balance a healthy boy by sitting at a further distance from the fulcrum, thereby increasing this turning effect.