Force-Driven Mass with Friction
Diagram and Equivalent Circuit

Force driving an ideal mass and dashpot

Equivalent Circuit

$$\begin{eqnarray*} 0 &=& -f(t) + f_m + f_\mu\\ [5pt] 0 &=& -f(t) + m\,\dot v(t) + \mu\, v(t) \end{eqnarray*}$$