On stretching a wire, the elastic energy stored per unit volume is

The elastic potential energy stored in a steel wire of length $20\,m$ stretched through $2 \,m$ is $80\,J$. The cross sectional area of the wire is $.........\,mm ^2$ (Given, $y =2.0 \times 10^{11}\,Nm ^{-2}$ )

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 steel rod of length $\ell$, cross sectional area $A$, young's modulus of elasticity $Y$, and thermal coefficient of linear expansion $'a'$ is heated so that its temperature increases by $t\,^oC$. Work that can be done by rod on heating will be

Two steel wires having same length are suspended from a ceiling under the same load. If the ratio of their energy stored per unit volume is $1: 4,$ the ratio of their diameters is

If the force constant of a wire is $K,$ the work done in increasing the length of the wire by $l$ is