In this chapter, we will study what is known as oscillatory motion. The study of oscillatory motion is basic to physics; its concepts are required for the understanding of many physical phenomena. For example, an AC power supply gives voltage that oscillates alternately going positive and negative about the mean value (zero).

The description of a periodic motion, in general, and oscillatory motion, in particular, requires some fundamental concepts, like period, frequency, displacement, amplitude, and phase.

What is Oscillatory Motion?

Oscillatory motion is defined as the to and fro motion of an object from its mean position. The ideal condition is that the object can be in oscillatory motion forever in the absence of friction but in the real world, this is not possible and the object has to settle into equilibrium.

In the mechanical world, the vibration of strings and movement of spring also comes under oscillatory motion and are the same as mechanical vibration. The oscillatory motion should not be confused with periodic motion. Objects in periodic motions repeat its motion after a fixed duration or period of time whereas, in oscillatory motion, the objects repeat their movement over a fixed position.

Examples of Oscillatory Motion

Oscillatory motion can be divided into two types. These are as follows:

Linear oscillatory motion

The object goes left and right or up and down in linear oscillatory motion. For example:

• The vibration of strings of musical instruments.
• Floating ships or large boats in the sea
• Fluid movement in a U-tube column

Circular oscillatory motion

The motion in which the object moves left to right in a circular way is called oscillatory motion. For example:

• The motion of a solid sphere in a half-hollow sphere. 
• Oscillation of simple pendulum.
• A wheel’s rotation.
• A string swinging from a nail.