A LevelMathsAQAMechanicsRevision NotesQuantities & Units in MechanicsQuantities, Units & ModellingTypes of Force

Types of Force (AQA A Level Maths: Mechanics): Revision Note

Exam code: 7357

Written by: Dan Finlay

Reviewed by: Lucy Kirkham

Updated on 2 July 2026

Types of force

What is a force?

A force is a vector quantity, it has both magnitude and direction
A force is a push or a pull on an object
A force is measured in Newtons
In A level mathematical models, forces act at a single point called a particle which occupies a single point in space

What types of force are used in mechanics?

Weight is the effect of mass and gravity, it always acts downwards
Tension is a pulling force, it always acts away from an object
Thrust is a pushing force, it always acts towards an object
Friction is a resistive force, it acts to oppose the motion of an object
Every surface will produce a reaction force, it will always act perpendicular to the surface

What is mass, gravity and weight?

Mass is a measure of the amount of matter in an object
- Mass is a scalar quantity, measured in kilograms, kg
- Mass is universal, it does not change based on location
Gravity is the force by which a body (usually a planet or a star) pulls objects towards its centre
- g is the acceleration due to gravity, measured in m s^-2
- On Earth, g is approximately 9.8 m s^-2 , although its exact value varies with location
- g is different elsewhere in the universe
Weight is the product of mass and gravity, it is a force measured in Newtons
- Weight is a vector quantity
- Weight varies with location
- Weight always acts vertically downwards towards the ground

Worked Example

The diagram below shows a car towing a trailer by a light inextensible string.

Forces D, R, F and T N act on the car and caravan as shown.

Write a brief description of what each force represents.

Diagram of a car pulling a trailer. Arrows indicate forces: R upwards on car, D left on car, F right on trailer, T tension between car and trailer.

Answer:

Examiner Tips and Tricks

There are many phrases/words that can be used implying the types of force
- Braking – suggests thrust
- Air resistance – suggests a resistive force
Always sketch a diagram and mark the forces on the diagram clearly
- It will help you understand the problem
- Add more things to the diagram as you progress through the question
- You may not even need all the forces from your diagram
The value used for g in questions tells you how you should round any answers
- If g = 9.8 m s^-2, use two significant figures
- If g = 10 m s^-2, use one significant figure

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