Friction

This lesson covers: 

  1. What friction is
  2. The advantages of friction
  3. The disadvantages of friction

What is friction?

Illustration showing a weight on a surface with arrows indicating friction and movement directions.

Friction is a force that opposes the relative motion between two surfaces that are in contact.

For example, when you try to move an object across a surface, friction pushes against the object in the opposite direction to its movement.

Advantages of friction

1. Friction allows motion to start and stop.

  • The friction between tyres and the road surface allows for acceleration, braking, and changing direction.
  • Without this friction, the tyres would slip.


2. Friction prevents slipping.

  • The friction between our hands and an object allows us to grip things.
  • For example, the friction between our hands and the handlebars on a bike lets us hold on while riding.

Disadvantages of friction 1

Diagram showing a car with arrows indicating friction and thrust forces.

1. Friction wastes energy.

  • Friction converts useful energy into heat energy which is wasted.
  • The heat generated in tyres is an example of this energy loss.

Disadvantages of friction 2

Illustration of a car showing air resistance and thrust forces acting on it.

2. Friction limits top speed.

  • At high speeds, air resistance is a form of friction which takes a lot of energy to overcome, limiting top speeds.
  • Aerodynamic shaping aims to minimise this frictional force.