Oscillatory motion a repetitive motion back and forth about an equilibrium position: swinging motions and vibrations of all kinds, all oscillatory motion is periodic. Oscillators objects or systems that undergo oscillatory motion: 2 characteristics: Oscillation takes place about an equilibrium position. Oscillations an object oscillates if the position as a function of time is a periodic function, i. e. it repeats. Of d-t graphs for oscillating systems [see diagram below: oscillations takes place around an equilibrium position the positive x-axis, the motion is periodic. One cycle takes time t: the 3rd oscillation is sinusoidal. Period (t) the time to complete one complete cycle: the time in seconds required to complete one full cycle or oscillation. Simple harmonic motion sinusoidal oscillation that is the most basic type of all oscillatory motions. Harmonic motion is described by a trigonometric function cos or sin.