Mechanical Equivalent of an Inductor is a Mass

The mechanical analog of an inductor is a mass. The voltage $v(t)$ across an inductor $L$ corresponds to the force $f(t)$ used to accelerate a mass $m$. The current $i(t)$ through in the inductor corresponds to the velocity ${\dot x}(t)$ of the mass. Thus, Eq. (C.4) corresponds to Newton's second law for an ideal mass:

$$f(t) = m a(t),$$

where $a(t)$ denotes the acceleration of the mass $m$.