If a spring extends by $x$ on loading, then the energy stored by the spring is (if $T$ is tension in the spring and $k$ is spring constant)

A block of mass $M$ is suspended from a wire of length $L$, area of cross-section $A$ and Young's modulus $Y$. The elastic potential energy stored in the wire is

When a $4\, kg$ mass is hung vertically on a light spring that obeys Hooke's law, the spring stretches by $2\, cms$. The work required to be done by an external agent in stretching this spring by $5\, cms$ will be ……… $joule$       $(g = 9.8\,metres/se{c^2})$

 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 $12\,\,\times\,\,10^{-6}\,/^oC$ . Its Young's modulus of elasticity is $10^{11}\,\,N/m^2$ . The energy stored per unit volume of rod will be  ……. $J/m^3$

The strain energy stored in a body of volume $V$ due to shear strain $\phi$ is (shear modulus is $\eta$ )