Friction is a force between two surfaces that are sliding, or trying to slide across each other. For example when you try to push a book along the floor friction makes this difficult.

Friction always slows a moving object down.object is moving, or trying to move.

Illustration of the forces involved in creating friction. Credit goes to BBC KS2 Bitesize
Illustration of the forces involved in creating friction. Credit goes to BBC KS2 Bitesize

The amount of friction depends on the materials from which the two surfaces are made.

The rougher the surface, the more friction is produced.

For example, you would have to push a book harder to get it moving on a carpet than you would on a wooden floor.

This is because there is more friction between the carpet and the book than there is between the wood and the book.

Friction produces heat. If you rub your hands together quickly, you will feel them get warmer.