Ideal Dashpot

Ideal dashpot characterized by a constant impedance $\mu$

• Dynamic friction law
  $$\begin{eqnarray*} f(t) &\approx& \mu v(t) \qquad \hbox{\lq\lq Ohm's Law''}\\ (\hbox{Force} &=& \hbox{Friction\_coefficient} \times \hbox{Velocity}) \end{eqnarray*}$$
  

• Impedance
  $$R_\mu(s) \isdef \mu \geq 0$$

• Dashpot = gain for force input and velocity output

• Electrical analogue: Resistor $R=\mu$

• More generally, losses due to friction are
  • frequency dependent
  • hysteretic