Forces - AQA GCSE Physics Revision

Topic overview

What you need to know

Forces is a key part of GCSE Physics. Choose the right model or equation, track units carefully and connect calculations to physical meaning. An object remains stationary or at constant velocity unless acted upon by a resultant force. Force = mass × acceleration (F = ma). The acceleration of an object is proportional to the resultant force and inversely proportional to mass. When two objects interact, the forces they exert on each other are equal and opposite.

Exam tip

Write the equation, substitute with units, calculate, then round only at the end.

Revision notes

Core ideas

Secure these ideas first. Say each definition in your own words, then connect it to the topic overview.

Newton's First Law: An object remains stationary or at constant velocity unless acted upon by a resultant force.
Newton's Second Law: Force = mass × acceleration (F = ma). The acceleration of an object is proportional to the resultant force and inversely proportional to mass.
Newton's Third Law: When two objects interact, the forces they exert on each other are equal and opposite.
Weight: The force of gravity acting on an object. W = mg (mass × gravitational field strength). Measured in newtons.

Revision notes

Apply it in the exam

The exam will rarely ask for an isolated definition. Practise selecting the right idea and using it as part of a complete explanation or method.

Resultant Force: The single force that has the same effect as all the forces acting on an object combined.
Stopping Distance: Total stopping distance = thinking distance + braking distance. Affected by speed, reaction time, road conditions.
Terminal Velocity: The maximum velocity reached when the driving force equals the resistive force (e.g. weight = air resistance for a skydiver).
Momentum: Momentum = mass × velocity (p = mv). Measured in kg m/s. Momentum is conserved in collisions.

Core knowledge

Key facts for Forces

8 essentials

Newton's First Law

An object remains stationary or at constant velocity unless acted upon by a resultant force.

Newton's Second Law

Force = mass × acceleration (F = ma). The acceleration of an object is proportional to the resultant force and inversely proportional to mass.

Newton's Third Law

When two objects interact, the forces they exert on each other are equal and opposite.

Weight

The force of gravity acting on an object. W = mg (mass × gravitational field strength). Measured in newtons.

Resultant Force

The single force that has the same effect as all the forces acting on an object combined.

Stopping Distance

Total stopping distance = thinking distance + braking distance. Affected by speed, reaction time, road conditions.

Terminal Velocity

The maximum velocity reached when the driving force equals the resistive force (e.g. weight = air resistance for a skydiver).

Momentum

Momentum = mass × velocity (p = mv). Measured in kg m/s. Momentum is conserved in collisions.

Active recall

Close the notes and answer these

1.Without looking, explain newton's first law and give one example or consequence.
2.Without looking, explain newton's second law and give one example or consequence.
3.Without looking, explain newton's third law and give one example or consequence.
4.Without looking, explain weight and give one example or consequence.

Content reviewed 23 July 2026 against the current linked specification.

Finished learning?

Mark the notes complete, then test what you can recall.

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