# Friction and its Types : Science

### Friction and its Types: NCERT / CBSE Revision Notes

Friction is a force that opposes the relative motion between two surfaces of objects in contact. The force of friction always acts in a direction opposite to that of the applied force. Friction is due to irregularities on the surfaces of the objects in contact.

Must Read : Force And Pressure

### Factors that affect friction are:

•     Roughness of the surface
•     Weight of the object
•     Nature of the surface

The force of friction increases if the surfaces are pressed harder.

### Types of friction are:

•     Static friction
•     Sliding friction
•     Rolling friction

#### Static friction

Frictional force that comes into action before the start of the motion of an object is called static friction.

#### Sliding friction

When an object slides over another surface, the frictional force that comes into action is sliding friction.

#### Rolling friction

When a roller rolls over a surface, the frictional force that comes into action is rolling friction.

Rolling friction is less than sliding friction, while sliding friction is less than static friction.

### Friction exists between two surfaces due to:

#### Fluid friction (Drag )

Friction due to gases and liquids is called fluid friction, and is also called drag.

Friction is a necessary evil. There are instances in daily life where friction is a necessity. For example, without friction, we cannot hold objects in our hands; we cannot walk and cannot light a match stick. Examples where friction has to be minimised and not desirable is the friction between machinery parts, which causes wear and tear.