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Moments - GCSE Physics Definition

Reviewed by: Ann Howell

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What is a moment?

In GCSE Physics, the moment of a force is the turning effect produced when a force is exerted on an object. Some examples of the rotation caused by the moment of a force are:

  • a child on a see-saw

  • turning the handle of a spanner

  • a door opening and closing

  • using a crane to move objects

  • using scissors

Diagram of a door showing greater force required near hinges and less force at the handle, with an arrow indicating pivot at the hinges.
A greater force is required to push open a door next to the hinges than at the door handle

Forces can cause the rotation of an object about a fixed pivot. This rotation can be described as either clockwise or anticlockwise. Applying a force on one side of the pivot will cause the object to rotate.

Two clocks illustrate motion: left shows clockwise with red arrow, right shows anticlockwise. Labels below read "CLOCKWISE" and "ANTICLOCKWISE".
Consider the hands of a clock when deciding if an object will rotate in a clockwise or anti-clockwise direction

The size of a moment, in newton metres, is defined by the equation:

moment space equals space force space cross times space distance

Where the force applied in newtons should be perpendicular to the distance in metres from the pivot.

Diagram of a spanner showing pivot point, the force applied, and the perpendicular distance from pivot to force, illustrating torque mechanics.
The moment depends on the force and perpendicular distance to the pivot.

Increasing the distance a force is applied from a pivot decreases the magnitude of the force required to create the moment. If you try to push open a door right next to the hinge it is very difficult, as it requires a lot of force. If you push the door open at the side furthest from the hinge then it is much easier as less force is required.

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Ann Howell

Reviewer: Ann Howell

Expertise: Physics Content Creator

Ann obtained her Maths and Physics degree from the University of Bath before completing her PGCE in Science and Maths teaching. She spent ten years teaching Maths and Physics to wonderful students from all around the world whilst living in China, Ethiopia and Nepal. Now based in beautiful Devon she is thrilled to be creating awesome Physics resources to make Physics more accessible and understandable for all students, no matter their schooling or background.

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