Moments & Equilibrium — A/L Physics

Moment of a Force (Torque) The turning effect of a force about a pivot. A moment is calculated as the product of the force and the perpendicular distance from the pivot to the line of action of the force. It is a vector quantity; its direction (clockwise or anticlockwise) must be specified. For example, pushing a door near the hinge requires more force than pushing at the handle because the perpendicular distance is smaller.

Principle of Moments For a body in rotational equilibrium, the sum of clockwise moments about any point equals the sum of anticlockwise moments about that same point. This principle applies only when there is no net angular acceleration. It is used to solve for unknown forces or distances in static systems, such as a balanced seesaw or a lever lifting a load.