K = FV / A ΔV = & DElta ; p V / V where , Δp = F / A = Change in pressure .
Its unit is N / m 2 or Pascal and its dimensional formula is [ ML -1 T -2 ]. 3 . Modulus of Rigidity ( η )
It is defined as the ratio of tangential stress to the shearing strain , within the elastic limit .
η = Tangential stress / Shearing strain Its urut is N / m 2 or Pascal and its dimensional formula is [ ML -1 T -2 ]. Compressibility Compressibility of a material is the reciprocal of its bulk modulus of elasticity . Compressibility ( C ) = 1 / k Its SI unit is N -1 m 2 and CGS unit is dyne -1 cm 2 .
Steel is more elastic than rubber . Solids are more elastic and gases are least elastic .
For liquids . modulus of rigidity is zero . Young ’ s modulus ( Y ) and modulus of rigidity ( η ) are possessed by solid materials only .
Limit of Elasticity
The maximum value of deforming force for which elasticity is present in the body is called its limit of elasticity .
Breaking Stress
The minimum value of stress required to break a wire , is called breaking stress .
Breaking stress is fixed for a material but breaking force varies with area of cross-section of the wire .
Safety factor = Breaking stress / Working stress