Problem 2: A cable has a length of 12 m and is stretched by 1.2 × 10-4 m when a stress of 8.0 × 108 Nm-2 is applied. What is the strain energy per unit volume in the cable when the stress is applied?
Given Length of the cable, L = 12 m
Stretching in the cable, Δl = 1.2 × 10-4 m
Stress applied = 8.0 × 108 Nm-2
Asked Strain energy per unit volume, u
Formula Strain energy per unit volume, u = ½ (stress × strain)
So we have to find strain first. Now
Now put the values of stress (given) and the strain (eq 1) in the formula,