Periodic Motion Any motion, which repeats itself in equal intervals of time is called periodic motion. Oftenly, the displacement of a particle in periodic motion can always be expressed in terms of sine and cosine functions. Since the term harmonic is applied to expressions containing these functions, If a particle in periodic motion moves back and forth (or to and fro) over the same path, then its motion is called oscillatory or vibratory . The examples of oscillatory or vibratory motion are: - the motion of a pendulum - the motion of a spring fixed at one end, which is stretched or compressed and then released - the motion of a violin string - the motion of atoms in molecules or in a solid lattice - the motion of air molecules as a sound wave passes by Characteristics of a Harmonic Motion The basic quantities characterizing a periodic motion are the amplitude, period and frequency of vibrations. Amplitude (A) The amplitude of oscillations is the maximum displa...
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