What is Friction? | Laws of Friction | Advantages

Obstruct the motion when one surface slide or tend to slide over the other surface is called as friction.

Frictional Force Diagram

Consider a block is kept on a horizontal rough surface and just moved by the force (P) as shown in fig.

friction and all force component of it


P = Applied force

R = Normal reaction offered by the horizontal surface in upward direction.

W = Weight of block acts vertically downwards.

F = Frictional force.


  • We can easily walk on the ground surface due to it.
  • Vehicle moving on road can be stopped by applying brakes by producing sufficient frictional force.
  • Hold writing material easily without slipping while writing on blackboard, slate or paper.
  • One can hammer the nail into wall due to This.


  • There is wear and tear to the surfaces of moving parts of various machine or equipment.
  • Loss of energy due to friction therefore efficiency of machine reduce.
  • Due to this consumption of fuel is more.
  • It reduces speed of the moving object.

laws of friction.

  • The frictional force act tangential at the common surface in contact between the two bodies as shown in fig.
  • And it always act in opposite direction to the direction of motion of a body.
  • This frictional force can be increased up to limiting friction.
  • When the body is just on the point motion.  It is in limiting equilibrium.
  • If body is in limiting equilibrium, then ratio of limiting friction and normal reaction is constant, which is termed as coefficient of friction(μ).
  • Static friction is always more than kinetic friction.

Coefficient of Friction(μ)

Definition –

The ratio of limiting fric. to normal reaction at the surface of contact is a constant which is called as coefficient of fric. and it is denoted by letter ‘μ’.

Download PDF of MCQ Questions

MCQ Question Is Taken From Bharat Skill Website Published By NIMI.

Objective questions on the above topics explain in the below video on YouTube.

Download PDF of this module Frictions.

Watch Below YouTube Videos For Detail Solutions.

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