What is the coefficient of viscosity? Give its unit.

(N/A) The force $F$ required to maintain the flow of layers in a liquid is given by the formula:
$F = \eta A \frac{dv}{dz}$
where $\eta = \frac{F}{A(dv/dz)}$.
Here,$\eta$ is the constant of proportionality and is called the coefficient of viscosity.
If the contact area $A = 1$ unit and the velocity gradient $\frac{dv}{dz} = 1$,then $\eta = F$.
Thus,the coefficient of viscosity $(\eta)$ is the force required when the velocity gradient and the contact area are unity.
Its $SI$ unit is $N \cdot s \cdot m^{-2}$ or $Pa \cdot s$ (Pascal-second).
In $kg \cdot m^{-1} \cdot s^{-1}$,the unit is $1 \ kg \cdot m^{-1} \cdot s^{-1} = 1 \ Pa \cdot s$.
The $CGS$ unit is $Poise$ $(P)$.
$1 \ P = 1 \ g \cdot cm^{-1} \cdot s^{-1} = 0.1 \ kg \cdot m^{-1} \cdot s^{-1}$.