Question

Define stress and strain and derive their units. Write one limitation of Hooke’s Law.

Answer 1

Stress is the deforming force experience by the body per unit area. 

Stress = \(\frac {F}{A}\)

Units = \(\frac {(N)}{(m^2)}\) = Nm^-2

Strain is the change in the considered quantity (l,v, A, θ.....) per unit of its original value.

Strain = \(\frac {Δx}{x}\)

It is unitless. 

Hooke’s Law is valid only for small deformation i.e., in its limit.