Friction Definition

In physics, friction is defined as the resistance that tends to stop the motion of an object from moving further. It is caused when the two surfaces of two irregular objects contact each other. For instance, when an object moves over the other object, the irregularities on both surfaces get entangled, which produces friction. The more irregular or rough the surface is, the more significant friction will be. Moreover, it is due to friction that we walk without slipping because it provides traction to our feet. The SI unit to measure friction is Newton (N).

Types of Friction

The types of friction are listed below:

  • Rolling friction

  • Static friction 

  • Fluid friction

  • Sliding Friction


Table of Contents

Formula of Friction

To find out the friction among two touching surfaces, you can use the formula listed below.

F = μ.N


F = the frictional force (measured in Newton)

μ = Dimensionless coefficient of friction (usually between 0-1, but in some cases, it can also be greater than 1.)

N = Normal force


If you want to calculate the friction, you can use our Friction Calculator.


For a more precise and clear understanding of the concept, let us solve an example below:

Suppose a force of 350N is acting upon a vehicle to move on the ground, where the value of the coefficient of friction is 0.13, then find out the friction acting upon a vehicle.

Given data

N = 350 N
Coefficient of friction = 0.13

To Find

Friction = ?


To find out the friction acting upon a vehicle, we will use the formula listed below;

F = μ.N

Putting values in the formula:

F = 0.13 × 350 = 45.5 N