ELASTICITY

The property of solid by virtue of which a solid body recovers its original shape after the removal of an applied force is called "ELASTICITY".

ELASTIC LIMIT: -

If applied force on a solid is gradually increased, a state is reached after which the material will not return to it original shape even after the removal of applied force. This limit is called "ELASTIC LIMIT".

After elastic limit, material is permanently deformed. Different substances have different elastic limit.

STRESS: -

When a body is deformed, the internal force came into play per unit area to restore it to its original state is called "STRESS"

OR

"Stress is an opposing force expressed per unit area which resists any change in shape."

Stress is equal to the force per unit area.

Mathematically: - Stress produces when a body is made to change in length, volume or Shape by the application of an external force. UNIT OF STRESS: - (i) N/m2 in S.I. System (ii) Dyne/cm2 in C.G.S. System. STRAIN: - "Strain is the fractional deformation produced in a body when it is subjected to a set of deforming forces." OR The change in length, volume or shape due to the application of a deforming force is called "Strain". OR "The fractional Deformation due to stress is called STRAIN." Strain has no unit because it is a ratio of two similar physical quantities. LONGITUDINAL STRAIN: - "The change in length per unit length of a body due to a deforming force is called LONGITUDINAL STRAIN" Mathematically: -