Identical springs of steel and copper are equally stretched. On which more work will have to be done?

An elastic material of Young's modulus $Y$ is subjected to a stress $S$. The elastic energy stored per unit volume of the material is

$A$ $5 \, m$ long wire is fixed to the ceiling. $A$ weight of $10 \, kg$ is hung at the lower end and is $1 \, m$ above the floor. The wire is elongated by $1 \, mm$. The energy stored in the wire due to stretching is ......... $J$.

If $S$ is stress and $Y$ is Young's modulus of the material of a wire,the energy stored in the wire per unit volume is

$A$ wire suspended vertically from one end is stretched by attaching a weight $200 \,N$ to the lower end. The weight stretches the wire by $1 \,mm$. The elastic potential energy gained by the wire is ....... $J$

$A$ wire of Young's modulus $1.6 \times 10^{12} \,N/m^{2}$ is stretched by a force so as to produce a strain of $2 \times 10^{-4}$. The energy density of the wire is