Newton's Third Law

This lesson covers Newton's third law as required by AQA GCSE Combined Science Trilogy (8464), section 6.5.3. This law explains why forces always occur in pairs and is frequently tested in the exam, particularly through questions about everyday situations.

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Statement of Newton's Third Law

Newton's third law: Whenever two objects interact, the forces they exert on each other are equal in magnitude and opposite in direction.

For every action, there is an equal and opposite reaction.

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Key Features of Third-Law Force Pairs

A Newton's third law pair must satisfy all of the following conditions:

Feature	Detail
Equal in magnitude	Both forces have the same size
Opposite in direction	The forces act in opposite directions
Same type	Both forces are the same kind (both gravitational, both contact, both electrostatic, etc.)
Act on different objects	One force acts on object A, the other on object B
Act simultaneously	Both forces exist at the same time