A steel wire of length 2 m and 1.2×10−7m2 in cross-sectional area is stretched by a force of 36 N. Calculate the work done  in ×10−2J stretching the wire Y=1.8×1011N/m2.

The stress in steel wire σ=FA=361.2×10−7=3×108N/m2As Young's modulus of elasticity, Y= Stress  Strain Strain = stress Y=3×1081.8×1011=53×10−3Workdone =12( stress )( strain ) volume                   =12×3×108×53×10−32×1.2×10−7=6×10−2 Joule.