WHAT IS ELASTICITY AND MICROSCOPIC REASON OF ELASTICITY

WHAT IS ELASTICITY 

We have use the concept of a a rigid solid body in which the distance between any two particles is always fixed. Real solid bodies do not exactly fulfil this condition. When external forces are applied, the body may get deformed. When deformed, internal forces develop which try to restore the body in its original shape. The extent to which the shape of a body is restored when the deforming force are removed varies from material to material. The property to restore the natural shape or oppose the deformation is called elasticity.

If a body completely gains its nature shape after the removal of the deforming forces, it is called a perfectly elastic body. If a body remains in the deformed state and does not even partially regain its original shape after the removal of the deforming forces, it is called a perfectly inelastic or plastic body.

Quite often, when the deforming forces are removed, the body partially regains the original shape. Such bodies are partially regains the original shape. Such bodies are partially elastic.

Microscopic Reason of Elasticity

A solid body is composed of a great many molecules or atom arranged in a particular fashion. Each molecule is acted upon by the force due to the neighbouring molecules. The solid taken such a shape that each molecule finds itself in a position of stable equilibrium. When the body is deformed, the molecules are displaced from their original positions of stable equilibrium. The intermolecular distances change and restoring force start acting on the molecules which drive them back to their original positions and the body taken its natural shape.

 One can  compare this situation to a spring-mass system. Consider a particle connected to several particles through springs. If this particle is displaced a little, the springs exert a resultant force which tries to bring the particle towards its natural position. In fact, the particle will oscillate about this position. In due course, the oscillations will be damped out and the particle will regain its original position.