Moment

Key Stage 3

Meaning

A moment is the turning effect of a force.

About Moments

When a force acts on an object with a pivot it becomes a turning force called a moment.

A moment can be calculated by multiplying a force by the distance from a pivot.

The units of a moment are Newton Metres (Nm).

Moments can be used to make Force Multipliers using a pivot and lever.

The longer the lever, the larger the moment that can be produced.

Using moments an effort can be used to lift a load. If the pivot is closer to the load than the effort then the force of effort can be smaller than the load to lift the object.

Equation

Moment = Force x Perpendicular distance from the pivot.

\[M = F \times d\] Where:

M = Moment

F = Force

d = Perpendicular distance from the pivot.

Example Calculations

A 20N force of effort is applied at a perpendicular distance of 0.15m from the pivot. Calculate the Moment.	A 20N force of effort is applied at a perpendicular distance of 14cm from the pivot. Calculate the Moment.	A 20N force of effort is applied at a perpendicular distance of 100mm from the pivot. Calculate the Moment.
Force = 20N Perpendicular distance = 0.15m \(M = F \times d\) \(M = 20 \times 0.15\) \(M = 3.0Nm\)	Force = 20N Perpendicular distance = 14cm = 0.14m \(M = F \times d\) \(M = 20 \times 0.14\) \(M = 2.8Nm\)	Force = 20N Perpendicular distance = 100mm = 0.10m \(M = F \times d\) \(M = 20 \times 0.10\) \(M = 2.0Nm\)
A 30N force of effort is applied at a perpendicular distance of 0.18m from the pivot. Calculate the Moment.	A 30N force of effort is applied at a perpendicular distance of 19cm from the pivot. Calculate the Moment.	A 30N force of effort is applied at a perpendicular distance of 200mm from the pivot. Calculate the Moment.
Force = 30N Perpendicular distance = 0.18m \(M = F \times d\) \(M = 30 \times 0.18\) \(M = 5.4Nm\)	Force = 30N Perpendicular distance = 19cm = 0.19m \(M = F \times d\) \(M = 30 \times 0.19\) \(M = 5.7Nm\)	Force = 30N Perpendicular distance = 200mm = 0.20m \(M = F \times d\) \(M = 30 \times 0.20\) \(M = 6.0Nm\)
The nail is a perpendicular distance of 0.02m away from the pivot. Calculate the Force applied to the nail.	The nail is a perpendicular distance of 4cm away from the pivot. Calculate the Force applied to the nail.	The nail is a perpendicular distance of 60mm away from the pivot. Calculate the Force applied to the nail.
Moment = 5.4N Perpendicular distance = 0.02m \(M = F \times d\) \(5.4 = F \times 0.02\) \(F = \tfrac{5.4}{0.02}\) \(M = 5.4Nm\)