# Friction Force Formula

Friction is a repelling force when one body is slipping through a surface. Friction is because of the contact between two surfaces. If frictional force is great, the movement of objects through the surface is not in a smooth manner. All through this movement, the kinetic energy is transformed to heat energy. Friction force is a derived force and not like gravitation i.e. a fundamental force. The formula for friction force is,



Where Ff is the friction, μ is the coefficient of friction force and  Fn is the normal force. It is a vector quantity.

Friction Force – Solved Examples

Problem 1: An object of mass 10kg is moving through a surface. Compute the friction force if the coefficient of friction is 0.2?

Known variables are,
m = 10kg and μ = 0.2
Friction force formula is,
Ff = μFn
Fn can be computed as,
Fn = mg
= 10×9.81 = 98.1N
So, Ff = 0.2×98.1 = 19.62N

Problem  2: Calculate the friction force of a 5kg body which is moving through a surface with a friction coefficient 0.3?