4.1 Contact & Non-Contact Forces

Question 1

What is a force?

Answer 1

A push or a pull on an object that is caused by it interacting with another object

Question 2

Normal contact forces

Answer 2

Normal contact forces are the ‘push’ forces that two touching objects always exert on each other. E.g. a cat sat on a chair - the cat pushes down on the chair and the chair pushes up on the cat.

Question 3

Friction

Answer 3

Friction is a contact force between two objects that tend to slide past each other. E.g. a book resting on a slope - friction acts on both the slope and the book in the direction that tries to prevent motion.

Question 4

Forces are classed as vector quantities. What does this mean?

Answer 4

They have both magnitude and direction

Question 5

Non-contact forces

Answer 5

Non-contact forces are forces between two objects that aren’t touching. The forces are instead caused by fields around the object interacting. Some examples of non-contact forces are: gravitational forces, electrostatic forces and magnetic forces.

Question 6

Gravitational forces (example)

Answer 6

E.g. the attractive forces between the Earth and the Sun

Question 7

Electrostatic forces

Answer 7

The attraction or repulsion of charges when their electric fields interact

Question 8

Magnetic forces

Answer 8

The attraction or repulsion between two magnets due to their magnetic fields

Question 9

What are three examples of contact forces?

Answer 9

• Normal contact force
• Tension force
• Friction force

Question 10

Is air resistance a contact or non-contact force? Explain why.

Answer 10

Air resistance is a contact force. This is because it is due to the physical contact (collisions) between an object and the particles in the air.