Stress & strain

Stress : When some external system of forces or loads act on a body ,the internal forces( equal & opposite) are setup various sections of the body, which resist the external forces .This internal forces per unit area at any section of the body is known as unit stress or simply stress.

             Stress,  σ = P/A   (where,  P = Force or load acting on the body , A= Cross-section  area of the body )

         S.I. unit of stress is expressed in Pascal (Pa). 

Strain : When a system force act on a body, it undergoes some deformation .This deformation per  unit length is known as unit strain or simply strain .

                 Strain,  ε =  δl/l (where, δl = change in length of the body , and  l = original length of body.)