Moments, levers and gears

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:

\(\text{moment of a force} = \text{force} × \text{distance} \)

\(M = F d\)

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.

A simple lever and a simple gear system can both be used to transmit the rotational effects of forces.

Students should be able to explain how levers and gears transmit the rotational effects of forces.