Contact and Non-Contact Forces

This lesson covers the two main categories of forces — contact forces and non-contact forces — as required by the AQA GCSE Physics specification (4.5.2). A force is a push, a pull, or a twist that can change the shape, speed, or direction of an object. Forces are measured in newtons (N) and are vector quantities, meaning they have both magnitude and direction.

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What Is a Force?

A force is an interaction between two objects that can cause an object to:

• Change speed — speed up or slow down.
• Change direction — turn or curve.
• Change shape — stretch, compress, bend, or deform.

Forces are measured using a newton meter (also called a spring balance). The SI unit of force is the newton (N).

Key facts:

• A force is a vector quantity — it has both magnitude and direction.
• Forces always occur in pairs — when object A exerts a force on object B, object B exerts an equal and opposite force on object A (Newton's third law).
• A force arrow shows the direction and relative size of a force.