Biomechanics is the study of human movement, which analyses the forces acting on the body. It explains how and why the body moves and also explains the relationship between bones and muscles.

To understand how force causes movement in the body, it is important to know what a pivot and a lever are:

  • Pivot – A point around which something rotates or turns
  • Lever – A bar that pivots around a fixed point

When a force acts on something that has a pivot, it creates a turning effect. This turning effect is known as a moment. Pivots, levers and moments are often involved when a force acts on the body. For example, the arm works as a lever, where the elbow is the pivot. So, when a force acts on the arm, there’s a moment.

We can calculate the moment of a force by using the equation:

  • M = Moment in newton metres (Nm)
  • F = Force in newtons (N)
  • d = Distance in metres (m)

So, the moment of a force is calculated by multiplying the force by the perpendicular distance from the pivot point to the line of action of the force. Perpendicular distance is the distance at a right angle from the pivot to the line of force.


The diagram below shows that the weight in the hand, which is a force, creates a moment when it is applied around the pivot point.

Calculate the moment of the force.

Weight = force of 12 N

Distance from the pivot = 0.3 m

  • M = F × d
  • M = 12 × 0.3
  • M = 3.6 Nm