For an elastic material with Young modulus $E$, a tensile stress $S$ is applied. Hooke’s law is obeyed. What is the expression for the elastic energy stored per unit volume of the material?
- A$\frac{E}{2S^2}$
- B$\frac{2E}{S^2}$
- C$\frac{S^2}{E}$
- D$\frac{S^2}{2E}$