Stress and it's types

Stress: It is defined as the restoring force acting per unit area of the body deformed by external force.

Stress = Restoring force/ Area = F/A
where F is restoring force and A is area of body.

Types of Stresses: Two types
1. Normal stress: The restoring force (or deforming force) acting per unit area normal to the surface of body is called the normal stress. For e.g. When a wire is pulled by a fores along the length of wire, the stress is normal stress.

Normal stress is of two types:

(।) Longitudinal tensile stress: If length of the body increases in the direction of applied force, then stress is called longitudinal tensile stress.

(ii) Compressional stress: If length of the body or volume of body decreases on applying deforming force, then restoring force per unit area is called compressional stress.

2. Tangential stress: The restoring force (or deforming force) acting per unit area tangential to the surface of body is called tangential stress.

Units of stress: 
CGS unit of stress is dyne/cm² and SI unit is N/m².