# Kinetic Friction Coefficient

Written by Jerry Ratzlaff on . Posted in Dimensionless Numbers

Kinetic friction coefficient, abbreviated as $$\mu_k$$, a dimensionless number, also called coefficient of kinetic friction, is the amount of force that resists motion at a constant velocity.

## Kinetic friction coefficient formula

$$\large{ \mu_k = \frac {f_k}{F_n} }$$
Symbol English Metric
$$\large{ \mu_k }$$  (Greek symbol mu) = kinetic friction coefficient $$\large{ dimensionless }$$
$$\large{ f_k }$$ = kinetic friction $$\large{ lbf }$$ $$\large{N}$$
$$\large{ F_n }$$ = normal force $$\large{ lbf }$$ $$\large{N}$$