Contact and Non-Contact Forces
Revise Contact and Non-Contact Forces for GCSE Physics with this free worksheet and full mark scheme — Foundation and Higher exam-style questions with worked answers for AQA, Edexcel and OCR. Contact forces such as friction need objects to touch, while non-contact forces such as gravity and magnetism act at a distance.
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These worksheets and mark schemes are original, written for Virtus Academy and checked against the current AQA, Edexcel and OCR specifications. Every worksheet comes with a full mark scheme.
Topic overview
A force is a push or a pull that acts on an object because of its interaction with another object. All forces are vectors, so they have magnitude and direction.
Forces are either contact or non-contact. In a contact force the objects are physically touching — friction, air resistance, tension and the normal contact force. In a non-contact force the objects are physically separated — gravitational, electrostatic and magnetic forces.
Forces always occur in interaction pairs. When two objects interact, they exert equal and opposite forces on each other. If a chair pushes up on a person, the person pushes down on the chair with an equal force in the opposite direction.
Revision notes
What a force is
A force is a push or a pull acting on an object due to its interaction with another object.
All forces are vectors, with both magnitude and direction. Force is measured in newtons.
Contact and non-contact
Contact forces: the objects are physically touching. Friction, air resistance, tension in a rope, and the normal contact force.
Non-contact forces: the objects are physically separated. Gravitational force, electrostatic force, and magnetic force.
Interaction pairs
When two objects interact, they exert equal and opposite forces on each other.
The two forces act on different objects. A chair pushing up on a person is paired with the person pushing down on the chair, equal in size and opposite in direction.
Key points
- A force is a push or a pull from an interaction.
- All forces are vectors.
- Contact forces require the objects to touch.
- Friction and tension are contact forces.
- Non-contact forces act at a distance.
- Interaction pairs are equal and opposite.
Worked examples
Example 1
State two contact forces and two non-contact forces. [4 marks]
Model answer
Contact: friction (1 mark) and air resistance or tension (1 mark). Non-contact: gravitational force (1 mark) and magnetic or electrostatic force (1 mark).
Example 2
Explain what is meant by an interaction pair of forces. [2 marks]
Model answer
When two objects interact they exert forces on each other that are equal in size and opposite in direction (1 mark), and the two forces act on different objects (1 mark).
Example 3
A book rests on a table. Describe the interaction pair involving the table. [2 marks]
Model answer
The table exerts an upward normal contact force on the book (1 mark), and the book exerts an equal downward force on the table (1 mark).
Common mistakes
Saying interaction pair forces act on the same object.
They act on different objects, which is why they do not cancel out.
Classifying gravity as a contact force.
Gravitational force acts at a distance, so it is non-contact.
Forgetting that force is a vector.
Direction matters and must be stated.
Saying the two forces are unequal.
They are always equal in size and opposite in direction.
Exam tips
- Learn examples of both contact and non-contact forces.
- Say the pair acts on different objects.
- Use newtons as the unit of force.
- Describe direction as well as magnitude.
Key terms
- Force
- A push or pull arising from an interaction.
- Contact force
- A force where the objects are touching.
- Non-contact force
- A force acting at a distance.
- Interaction pair
- Two equal and opposite forces on different objects.
Related topics
Written and reviewed against the current AQA, Edexcel and OCR specifications. Spotted an error? Let us know.