Elasticity
Elasticity: Elasticity is the property of material of a
body by virtue of which the body acquires its original shape and size after the
removal of deforming force.
Elastic Limit:
Elastic limit is the maximum value of deforming force up to which a material
shows elastic property and above which the material looses its elastic
property.
Stress: The
restoring force per unit area set up inside the body subjected to deforming
force is called stress.
Strain: The
relative change in dimension or shape of a body which is subjected to stress is
called strain.
It is measured by ratio of change in length to the original
length (longitudinal strain), change in volume to original volume (volume
strain).
Hooke’s law: Under elastic limit, stress is proportional to
strain.
i.e. stress α
strain or stress/strain = E
(constant)
E is called elastic constant or modulus of elasticity. Its
value is different for different material. Its SI unit is N/m2 also
called Pascal.
Elastic constant is of three types:
(i)
Young’s modulus of elasticity Y = Longitudinal stress/ Longitudinal strain
(ii)
Bulk modulus of elasticity K = Volume stress/ Volume strain
(iii)
Rigidity modulus (ɳ) Tangential (or shear) stress/
shear strain
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