Friction

Friction is the force which opposes the motion of an object.

It’s a type of resistive force (a force which opposes motion).

Direction of action

Frictional forces act in the opposite direction to the motion of an object.

When does friction occur?

Friction occurs when an object is moving, or trying to move, across a surface.

It’s basically when the surface of an object is rubbing against another surface, causing a force which opposes the motion of the object.

A thing to keep in mind is that friction can only oppose an existing force or motion. It can’t create a force or motion on its own - so basically, it can only slow down an object rather than actually make it move.

Types of friction

There are two main types of friction:

• Static friction - the frictional force which opposes the motion of an object which is not moving. It acts to prevent an object from starting to move.
• Kinetic friction - the frictional force which opposes the motion of an object which is moving. It acts to slow down an object which is already moving.