The work done in increasing the length of a $1$ $metre$ long wire of cross-section area $1\, mm^2$ through $1\, mm$ will be ....... $J$ $(Y = 2\times10^{11}\, Nm^{-2})$

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 $10^{11} \,{Nm}^{-2}$ ))

When strain is produced in a body within elastic limit, its internal energy

Two wires of the same material (Young's modulus  $Y$ ) and same length $L$  but radii  $R$  and  $2R$  respectively are joined end to end and a weight  $W$  is suspended from the combination as shown in the figure. The elastic potential energy in the system is

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

A wire suspended vertically from one of its ends is stretched by attaching a weight of $200\ N$ to the lower end. The weight stretches the wire by $1\ mm$. Then the elastic energy stored in the wire ......... $J$