# Kinetic Friction

Written by Jerry Ratzlaff on . Posted in Kinematics

Kinetic friction, abbreviated as fk, also called dynamic friction or sliding friction, is the force opposing two objects rubbing together that are moving relative to each other. It is calculated using the normal force, which is the force perpendicular to the surface that the objects contact.

### Kinetic Friction formula

$$\large{ f_k = \mu_k \; F_n }$$

Where:

$$\large{ f_k }$$ = kinetic friction

$$\large{ \mu_k }$$ (Greek symbol mu) = kinetic friction coefficient

$$\large{ F_n }$$ = normal force

Solve for:

$$\large{ \mu _k = \frac {f_k}{F_n} }$$

$$\large{ F_n = \frac {f_k}{\mu_k} }$$