In the previous chapter, we encountered a number of energy conserving physical systems that
exhibit simple harmonic oscillation about a stable equilibrium state. One of
the main features of such oscillation is that, once
excited, it never dies away. However, the majority of the oscillatory
systems that we encounter in everyday life suffer some sort of irreversible energy loss while they are in motion, due, for instance, to frictional or viscous heat generation. We would therefore expect oscillations excited in such systems
eventually to be damped away. The aim of this chapter is to examine so-called damped harmonic
oscillation, and also to introduce the differential equation that governs such motion, which is
known as the damped harmonic oscillator equation. In addition, we shall examine the
phenomenon of resonance in periodically driven, damped, oscillating systems. In this
chapter, examples are again drawn from simple mechanical and electrical systems.
