Oscillatory Motion - Definition, Examples, Types, FAQs

What is Oscillatory Motion?

Definition: An oscillatory motion is a to-and-fro or back-and-forth motion of a body about a fixed position or mean position.
In this motion, the body repeats its path at regular intervals of time.

Examples of Oscillatory Motion

1. Motion of a simple pendulum
2. Vibrating strings of a guitar
3. Oscillation of a tuning fork
4. The motion of a swing
5. Spring mass system
6. Bungee jumping
7. A suspension bridge under variable load

Types of Oscillatory Motion

Based on the nature of motion, oscillatory motion can be classified into two types:

1. Linear Oscillatory Motion
2. Circular Oscillatory Motion

Linear Oscillatory Motion

The oscillatory motion occurs in a linear path ( straight line) around the equilibrium position. The displacement is measured in meters or any unit of length. The restoring force is proportional to the displacement.

$
F=-k x
$

Examples of linear oscillatory motion

• Spring-mass system
• Vibration on a string
• The piston in an engine
• Bungee jumping

Circular Oscillatory Motion

The oscillatory motion is in back-and-forth rotation about a fixed axis. The displacement is measured as an angle. The restoring torque is proportional to the angular displacement.

$
\tau=-k \theta
$

Examples of Circular Oscillatory Motion

• Swinging doors
• Rotating flywheel
• Balance wheel in clocks

Characteristics of Oscillatory Motion

• Oscillatory motion occurs at a fixed point where the net force acting is zero. This position is called the equilibrium position.
• The fixed interval of time at which the oscillatory motion repeats itself is called the time period.
• The maximum displacement from the equilibrium position called amplitude measures the extent of oscillation.
• Frequency is the number of oscillations completed per second.

$$f=\frac{1}{T}$$

• Oscillatory systems have both kinetic energy and potential energy.

Simple Harmonic Motion

Simple harmonic motion is a type of oscillatory motion in which Hooke's law is obeyed. In this motion, the restoring force is directly proportional and opposite to the displacement from the equilibrium position of the motion.

$
F=-k x
$

where,

• $F$ is the spring's restoring elastic force ($N$),
• $k$ is the spring constant ($\mathrm{Nm}^{-1}$),
• $x$ is the displacement from the equilibrium position ($m$)

Examples of SHM

• Vibrating strings
• LC circuit
• Torsional pendulum

The oscillatory motion's equilibrium position is the place at which oscillations occur, and the oscillating object must pass through this point during each oscillation. The oscillating object comes to a stop at this point after some time when the oscillatory motion stops due to friction in the medium in which it is oscillating.

Vibration is a term used to describe objects that oscillate. There isn't much of a distinction between these two terms. However, in general, when an object moves at high frequencies, it is said to be vibrating, and when it moves at low frequencies, it is said to be oscillating.

To and Fro Motion

The forward and backward movement of an object around an equilibrium point is referred to as to and fro. A pendulum, for example, travels from one side to the other before returning to its original position. To and fro motion is the term for this type of movement.

What is Periodic Motion

Definition: A periodic motion is a motion that repeats itself at regular intervals of time.
In this type of motion, a body moves in such a way that its position, velocity, and acceleration repeat after a fixed time period.

Examples:

• The revolution of the Earth around the Sun (1 year).
• The rotation of the Earth about its axis (1 day).
• The motion of a pendulum.
• The vibration of a tuning fork.

The Difference Between Periodic Motion and Oscillatory Motion

The differences between oscillatory and periodic motions are given in the table below:

Related Topics,

• Loudness of Sound
• Periodic Motion
• Period and Angular Frequency
• Resonance