English Physicist Robert Hook in the year 1676 put forward the relation between the extension produced in a wire and the restoring force developed in it. The law formulated on the basis of this study is known as Hooke’s law.

According to Hooke’s law, within the elastic limit, the stress developed is directly proportional on the strain. It unit is Nm^-2

stress α strain

a constant, known as modulus of elasticity.