Elastic Property of Matter – some definitions

In this post, we will present some important definitions related to the Elastic property of matter (from the Elasticity chapter).

definitions related to the Elastic property of matter (or Elasticity chapter)

(1) Elasticity: The property of matter by virtue of which a body tends to regain its original shape and size after the removal of deforming force is called elasticity.

(2) Plasticity: The property of matter by virtue of which it does not regain its original shape and size after the removal of deforming force is called plasticity.

(3) Perfectly elastic body: If on the removal of deforming forces the body regains its original configuration completely it is said to be perfectly elastic.
A quartz fiber and phosphor is the nearest approach to the perfectly elastic body.

(4) Perfectly plastic body: If the body does not have any tendency to recover its original configuration on the removal of deforming force, it is said to be perfectly plastic.
Paraffin wax, & wet clay are the nearest approach to the perfectly plastic body. Practically there is no material that is either perfectly elastic or perfectly plastic.

(5) Reason for elasticity: On applying the deforming forces, restoring forces are developed. When the deforming force is removed, these restoring forces bring the molecules of the solid to their respective equilibrium position, and hence the body regains its original form.

(6) Elastic limit: The maximum deforming force up to which a body retains its property of elasticity is called the elastic limit of the material of the body.
Elastic limit is the property of a body whereas elasticity is the property of the material of the body.

(7) Elastic fatigue: The temporary loss of elastic properties because of the action of repeated alternating deforming force is called elastic fatigue.
It is due to this reason :
(i) Bridges are declared unsafe after a long time of their use.
(ii) Spring balances show wrong readings after they have been used for a long time.
(iii) We are able to break the wire by repeated bending.

(8) Elastic after effect: The time delay in which the substance regains its original condition after the removal of deforming force is called elastic after effect. It is negligible for perfectly elastic substances, like quartz,
phosphor bronze and large for glass fiber.