Physics - Elasticity Question with Solution | TestHub

For a spring, the restoring force is $F=kx$, where $k$ is the spring constant.

The elastic potential energy stored in the spring is the work done in stretching it, which is given by the integral of force with respect to displacement.$$U={\int }_0^{x}Fdx={\int }_0^{x}kxdx=\frac{1}{2}k{x}^2$$