A force or a system of forces may cause an object to rotate. Students should be able to describe examples in which forces cause rotation. • The turning effect of a force is called the moment of the force. The size of the moment is defined by the equation: moment of a force = force × distance, M = F d. moment of a force, M, in newton-metres, Nm; force, F, in newtons, N; distance, d, is the perpendicular distance from the pivot to the line of action of the force, in metres, m. • If an object is balanced, the total clockwise moment about a pivot equals the total anticlockwise moment about that pivot. • Students should be able to calculate the size of a force, or its distance from a pivot, acting on an object that is balanced.