Hooke's law of elasticity states that for small deformation (within proportionality limit) the stress is directly proportional to strain. The constant of proportionality is called the modulus of elasticity. Note: There are three elastic moduli based on the type of stress. They are (i) Young's modulus, (ii) Shear modulus and (iii) Bulk modulus. Hooke’s law is an empirical law and is found to be valid for most materials.

It is given by the ratio of pressure applied to the corresponding relative decrease in the volume of the material. Mathematically, it is represented as follows: B = Δ P / ( Δ V / V ) Where: B : Bulk modulus Δ P : change of the pressure or force applied per unit area on the material Δ V : change of the volume of the material due to the compression V : Initial volume of the material.