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.

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Factors that affect friction are:

    Friction and its Types, CBSE / NCERT Revision Notes, MCQs, Solutions
  •     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:

  •     Irregular/uneven surfaces
  •     Interlocking of micro-level irregularities of two surfaces
  •     Ploughing of harder surfaces into smoother surfaces


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.

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