Strain and Its Types (Physics)

Strain is the deformation (change in shape or size) of a body when a force is applied. It tells us how much an object changes compared to its original size.

In simple words:

Strain = Change in dimension / Original dimension

So mathematically:

Strain=Change in dimension/Original dimension​

Strain has no unit because it is a ratio of two similar quantities.

Types of Strain

There are mainly three types of strain:

1. Longitudinal Strain

When the length of a body changes due to a force applied along its length, it is called longitudinal strain.

Formula:

Longitudinal Strain=Change in length/Original length

This strain is of two types:

• Tensile Strain – when the object stretches and its length increases.
  Example: Stretching a rubber band.

• Compressive Strain – when the object compresses and its length decreases.
  Example: Pressing a spring.

2. Volumetric Strain

When the volume of a body changes due to pressure or force from all sides, it is called volumetric strain.

Formula:

Volumetric Strain=Change in volume/Original volume

Example:
When a ball is squeezed from all directions.

3. Shear Strain (Angular Strain)

When a force is applied parallel to the surface of a body, causing the shape to change without much change in volume, it is called shear strain.

Example:
Pushing the top of a deck of cards sideways.

Summary