A metal wire of length $'L'$ is suspended vertically from a rigid support. When a body  of mass $M$ is attached to the lower end of wire, the elongation in wire is $'l'$, consider the following statements 

$(I)$  the loss of gravitational potential energy of mass $M$ is $Mgl$

$(II)$ the elastic potential energy stored in the wire is $Mgl$

$(III)$ the elastic potential energy stored in wire is $\frac{1}{2}\, Mg l$

$(IV)$ heat produced is $\frac{1}{2}\, Mg l$ 

Correct statement are :-

The work per unit volume to stretch the length by $1\%$ of a wire with cross sectional area of $1\,m{m^2}$ will be. $[Y = 9 \times {10^{11}}\,N/{m^2}]$

A uniform metal rod of $2\, mm^2$ cross section fixed between two walls is heated from $0\,^oC$ to $20\,^oC$. The coefficient of linear expansion of rod is $12\times10^{-6}/^oC$. Its Young's modulus of elasticity is $10^{11} \,N/m^2$. The energy stored per unit volume of rod will be ....... $J/m^3$

A stretched rubber has

A suspended long metal wire is stretched a small distance $x$ by a load $W$ in newton suspended at the other end. Select the best answer out of the following

A metal wire having Poisson's ratio $1 / 4$ and Young's modulus $8 \times 10^{10} \,N / m ^2$ is stretched by a force, which produces a lateral strain of $0.02 \%$ in it. The elastic potential energy stored per unit volume in wire is [in $\left.J / m ^3\right]$