AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Describe examples of the forces acting on an isolated object or system
Full specification wording
Resultant forces: describe examples of the forces acting on an isolated object or system
An isolated object or system is one considered on its own, allowing you to describe the external forces acting upon it.
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 3 of 6
- 4 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
An isolated object or system is one considered on its own, allowing you to describe the external forces acting upon it. These forces can be balanced or unbalanced; an isolated object can have a resultant force and accelerate. For a single object, identify every force by its type and direction: a book resting on a table has weight acting downwards and a normal contact force acting upwards. For a moving car, list the driving force forwards, drag backwards, weight downwards and normal contact force upwards. State the direction and whether each force is a push or a pull. Describing means naming the forces and giving their directions, using free-body diagrams to model the forces acting on the isolated object.
What earns the marks
- Names each external force acting on the isolated object or system, such as weight, normal contact force, friction, drag or tension.
- States the direction of each force, for example weight acts vertically downwards and the normal contact force acts vertically upwards.
- Identifies the object or part of the system that exerts each force, such as the table pushing up on the book.
- Recognises that an isolated object can have unbalanced external forces leading to a resultant force and acceleration.
- Uses correct force vocabulary rather than everyday words, for example drag instead of air resistance where appropriate.
Common mistakes and how to put them right
Assuming an isolated object must have balanced forces.
Put it right by recognising that isolated objects can experience a resultant force and accelerate.
Labelling weight and mass as the same quantity.
Put it right by stating that weight is a force in newtons acting downwards while mass is in kilograms.
Omitting the normal contact force on an object resting on a surface.
Put it right by including the upward contact force from the surface.
Exam tips
- Name the object first, then list each force with its direction and the body that exerts it.
- Use a labelled free-body diagram to support your written description, ensuring arrows start from the object.
Try the lesson
The start of the Resultant forces: describe examples of the forces acting on an isolated object or system lesson, made from checked teaching notes for this specification point.
Have a go first
A book is resting on a horizontal table. Which pair of forces acts on the book?
Listen
An isolated object or system is one considered on its own, allowing you to describe the external forces acting upon it. These forces can be balanced or unbalanced; an isolated object can have a resultant force and accelerate. For a single object, identify every force by its type and direction: a book resting on a table has weight acting downwards and a normal contact force acting upwards. For a moving car, list the driving force forwards, drag backwards, weight downwards and normal contact force upwards. State the direction and whether each force is a push or a pull. Describing means naming the forces and giving their directions, using free-body diagrams to model the forces acting on the isolated object. A strong answer earns marks for these points. Names each external force acting on the isolated object or system, such as weight, normal contact force, friction, drag or tension. States the direction of each force, for example weight acts vertically downwards and the normal contact force acts vertically upwards. Identifies the object or part of the system that exerts each force, such as the table pushing up on the book. Recognises that an isolated object can have unbalanced external forces leading to a resultant force and acceleration. A common slip: Assuming an isolated object must have balanced forces. Instead, recognising that isolated objects can experience a resultant force and accelerate. Exam tip: Name the object first, then list each force with its direction and the body that exerts it.
See it
Key words
Say what each word means before you turn the card.
Isolated object or system
Try answering aloud or in your head before turning the card.
External forces
Try answering aloud or in your head before turning the card.
Resultant force
Try answering aloud or in your head before turning the card.
Free-body diagrams
Try answering aloud or in your head before turning the card.
See every definition
- Isolated object or system
- One considered on its own, allowing you to describe the external forces acting upon it.
- External forces
- The forces acting upon an isolated object or system, which can be balanced or unbalanced.
- Resultant force
- What an isolated object can have when its external forces are unbalanced, leading to acceleration.
- Free-body diagrams
- Used to model the forces acting on the isolated object when describing them.
Label the diagram
Some boxes have lost their names. Pick the right name for each number.
1Box 1
2Box 2
3Box 3
There is more to this lesson
The full lesson goes on to check your understanding and help you earn the marks. Create a free account to carry on, with your progress saved.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge
Test your understanding of Resultant forces: describe examples of the forces acting on an isolated object or system
Active recall beats re-reading. Take an instant quiz now to test what you’ve learned and lock it into long-term memory.
A week of Premium from your first lesson · Then the free plan continues · No card, no charge