Introduction

What this chapter is about

Oscillation is one of the commonest motions in nature — the rocking of a cradle, the swinging of a swing, the pendulum of a clock, a vibrating guitar string, the needle of a sewing machine, the prongs of a tuning fork, a spring loaded with a mass. In all of these the motion repeats after a definite interval of time, so it is a periodic motion, and the motion itself is mostly to and fro or up and down.

Oscillatory motion is a periodic motion. For the special kind studied here, the displacement, velocity and acceleration can all be written using sine and cosine functions. These are called harmonic functions, so an oscillatory motion that obeys them is called harmonic motion.

What you should be able to do after it

• Use the right terms for oscillations — period, frequency, amplitude, phase, epoch.
• Define and analyse simple harmonic motion (S.H.M.), both linear and angular.
• Draw and read the graphical representations of S.H.M.
• Describe the energy changes during S.H.M.
• Explain damping of oscillations, forced oscillations and resonance.