Forces and Motion: Principle of Moments

The principle of moments explains the turning effect produced by a force.
It states that for an object to be in equilibrium (not turning), the sum of the clockwork moments must equal the sum of the anti-clockwise moments.
A moment is calculated by multiplying the force applied by the perpendicular distance from the pivot point to the line of action of the force.
The unit of moment is Newton-metre (Nm).
Increasing the force or the distance from the pivot will increase the moment.
Examining leverage, a smaller force can have a greater moment if its distance from the pivot is larger.
Centre of mass is the point where weight can be considered as acting.
If freely suspended, an object will come to rest with its centre of mass directly beneath the point of suspension.
If an object is balanced on a point, that point must be vertically below the centre of mass.
The stability of an object is affected by the position of its centre of mass; a lower centre of mass tends to make an object more stable.
Knowledge of the principle of moments is useful for understanding how tools such as levers and gears work.
Forces have both magnitude and direction, making them vector quantities. Both of these will affect the resultant moment on an object.