AQA · GCSE · Combined Science
Course version: 8464 · Version from Sept 2018
Contact forces – the objects are physically touching
Full specification wording
Contact and non-contact forces: contact forces – the objects are physically touching
A contact force is any force that acts between two objects only because their surfaces or bodies are physically touching.
Checked against the AQA 8464 specification (opens in a new tab) on .
- Point 2 of 7
- 2 key terms
Study notes
From the checked teaching notes for this specification point.
The idea
A contact force is any force that acts between two objects only because their surfaces or bodies are physically touching. The interaction is transmitted at the point of contact, so if the objects are separated, the force disappears. Friction, air resistance, water resistance, tension in a rope, normal contact force from a floor and the push of a hand on a box are all contact forces. To identify one, trace the force to the touching surfaces: for example, a book resting on a table pushes down on the table and the table pushes up on the book, and both forces require the surfaces to meet. When drawing free-body diagrams, contact forces are drawn at the contact point, whereas non-contact forces act at a distance.
What earns the marks
- States that a contact force requires the objects to be physically touching at the point where the force acts.
- Gives a correct example such as friction, air resistance, water resistance, tension, normal contact force or a push/pull from direct contact.
- Explains that if the objects are separated, the contact force is no longer exerted.
- Distinguishes contact forces from non-contact forces by referring to physical touching rather than distance.
- Applies the idea to a diagram or scenario, for example identifying the normal contact force between a book and a table.
Common mistakes and how to put them right
Saying that gravity is a contact force because objects feel heavy.
Put it right by noting that gravity acts at a distance and is non-contact.
Confusing air resistance with a non-contact force.
Put it right by explaining that air resistance arises from collisions between moving surfaces and air particles, so it is contact.
Drawing a contact force away from the contact point.
Put it right by placing the arrow at the surface where the objects touch.
Exam tips
- Underline the words physically touching in the question so you remember the defining condition.
- When asked to classify a force, name the two objects and state where they touch before deciding.
- Use a quick sketch with arrows at the contact point to support your written answer.
Try the lesson
The start of the Contact and non-contact forces: contact forces – the objects are physically touching lesson, made from checked teaching notes for this specification point.
Have a go first
Which statement describes a contact force?
Listen
A contact force is any force that acts between two objects only because their surfaces or bodies are physically touching. The interaction is transmitted at the point of contact, so if the objects are separated, the force disappears. Friction, air resistance, water resistance, tension in a rope, normal contact force from a floor and the push of a hand on a box are all contact forces. To identify one, trace the force to the touching surfaces: for example, a book resting on a table pushes down on the table and the table pushes up on the book, and both forces require the surfaces to meet. When drawing free-body diagrams, contact forces are drawn at the contact point, whereas non-contact forces act at a distance. A strong answer earns marks for these points. States that a contact force requires the objects to be physically touching at the point where the force acts. Gives a correct example such as friction, air resistance, water resistance, tension, normal contact force or a push/pull from direct contact. Explains that if the objects are separated, the contact force is no longer exerted. Distinguishes contact forces from non-contact forces by referring to physical touching rather than distance. A common slip: Saying that gravity is a contact force because objects feel heavy. Instead, noting that gravity acts at a distance and is non-contact. Exam tip: Underline the words physically touching in the question so you remember the defining condition.
See it
Key words
Say what each word means before you turn the card.
Contact force
Try answering aloud or in your head before turning the card.
Non-contact forces
Try answering aloud or in your head before turning the card.
See every definition
- Contact force
- Any force that acts between two objects only because their surfaces or bodies are physically touching.
- Non-contact forces
- Forces that act at a distance rather than by physical touching, in contrast to contact forces.
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