**Vibration Model**

The basic vibration model of a
simple oscillatory system consists of a mass, a massless spring, and a damper. The spring
supporting the mass is assumed to be of negligible mass. Its force-deflection relationship
is considered to be linear, following Hooke's law, , where
the stiffness k is measured in newtons/meter.

The viscous damping, generally
represented by a dashpot, is described by a force proportional to the velocity, or . The damping coefficient c is measured in newtons/meter/second.