Key learning points

1. Friction is the force between two surfaces that are moving, or trying to move, across each other.
2. Friction always acts in the opposite direction to the movement of an object.
3. Only changing one variable ensures that no other factor affects the test results.

Keywords

• Surface - The surface is the top or outside layer of an object or material.

• Force - A force is a push or a pull. Forces can make objects move, change speed, change direction or change shape.

• Friction - Friction is a force that acts between surfaces.

• Variable - A variable is something that can be changed, measured or kept the same in an investigation.

Common misconception