The stress induced in a body, when subjected to two equal and opposite pulls as shown in figure (a)
as a result of which there is an increase in length, is known as tensile stress.
P = Pull acting on the body, A = Cross sectional area of the body,
σ= Stress induced in body
Figure (a), shows a bar which is subjected to tensile force P at its ends. Consider section x-x that divides the bar into two parts. The part left to section x-x, will be in equilibrium if P = Resisting force (R). This is show in Figure (b), Similarly the part right to the section x-x, will be in equilibrium if P = Resisting force as shown in Figure (c), This resisting force per unit area is known as stress or intensity of stress. Tensile stress ( σ ) = Resisting force (R)/Cross sectional area σ1 = P/A N/m2.