# 4.4.3 Newton's Third Law

### Newton's Third Law

• Newton’s Third Law states:

If body A exerts a force on body B, then body B will exert a force on body A of equal magnitude but in the opposite direction

• This means that every force has a paired equal and opposite force
• Newton’s Third Law force pairs must act on two different objects
• Newton’s Third Law force pairs must also be of the same type e.g. gravitational or frictional

#### Worked Example

Using Newton’s third law describe why when a balloon is united, it travels in the opposite direction.

#### Exam Tip

You may have heard Newton’s Third Law as: ‘For every action is an equal and opposite reaction’. However, try and avoid using this definition since it is unclear on what the forces are acting on and can be misleading.

Newton’s Third Law force pairs are only those that act on different objects

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Ashika graduated with a first-class Physics degree from Manchester University and, having worked as a software engineer, focused on Physics education, creating engaging content to help students across all levels. Now an experienced GCSE and A Level Physics and Maths tutor, Ashika helps to grow and improve our Physics resources.
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