Write the unit of the coefficient of static friction.

(NONE) The coefficient of static friction,denoted by $\mu_s$,is defined by the relation $f_s = \mu_s N$,where $f_s$ is the static frictional force and $N$ is the normal force.
Rearranging this formula,we get $\mu_s = \frac{f_s}{N}$.
Since both $f_s$ and $N$ are forces,they are measured in Newtons $(N)$.
Therefore,the unit of $\mu_s$ is $\frac{N}{N} = 1$.
This means the coefficient of static friction is a dimensionless quantity and has no unit.