Calculate the height to which the stone of mass $10 \mathrm{g}$ should be raised so that its potential energy becomes $0.49 \mathrm{J}$. ($g = 9.8 \frac{\mathrm{m}}{{\mathrm{s}}^2}$)

State an example of renewable resource.

A spring of spring constant $\mathrm{K}= 4\mathrm{x}{10}^3\mathrm{N}/\mathrm{m}$ is compressed by $2 \mathrm{cm}$, then determine the potential energy stored in spring. 

Ratio of potential energies of body A and body B will be