Friction

Friction is a force that resists the motion of one surface sliding or rolling over another.

Effects

Friction slows down moving objects and produces heat. It allows us to walk without slipping and lets vehicles grip the road, but it also causes wear and wastes energy in machines.

Reducing friction

Lubricants such as oil, and smooth surfaces or wheels, reduce friction where it is unwanted.

Frequently asked questions

What is friction?

The force that resists motion between two surfaces in contact.

Is friction useful?

Yes — it lets us walk and grip things, though it also causes wear.