# Equations of Motion — Lesson 2

The key aspect of a time-domain analysis is the solution for full governing equations including the acceleration, velocity and displacement terms.

Each of these terms influences the time-dependent behavior. For instance, the inertial term stores the kinetic energy of a system. A fidget spinner is a good example of this phenomenon.

The damping term is responsible for dissipating a portion of the kinetic energy of the system as heat energy. A shock absorber is a typical example that "absorbs" a shock by dissipating the kinetic energy of the shock as heat energy.

The stiffness term carries the potential energy and may introduce time-dependent behavior by dissipating a portion of potential energy in the form of heat energy. This may be due to time-dependent behavior such as viscoelastic or visco-plastic material behavior. Such behavior is commonly seen in soldered electronic components.

In this lesson, we will learn how each of these terms affects the energy of a system and, in turn, results in a time-dependent response.