When load of $5\,kg$ is hung on a wire then extension of $3\,m$ takes place, then work done will be ....... $joule$

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 area of cross-section of a railway track is $0.01\, {m}^{2}$. The temperature variation is $10^{\circ} {C}$. Coefficient of linear expansion of material of track is $10^{-5} /{ }^{\circ} {C}$. The energy stored per meter in the track is ...... ${J} / {m} .$

(Young's modulus of material of track is $10^{11} \,{Nm}^{-2}$ ))

Two wires of same diameter of the same material having the length $l$ and $2l.$ If the force $  F$ is applied on each, the ratio of the work done in the two wires will be

The work done per unit volume to stretch the length of area of cross-section $2 \,mm ^2$ by $2 \%$ will be ....... $MJ / m ^3$ $\left[Y=8 \times 10^{10} \,N / m ^2\right]$

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