d
\(\mathrm{k} \Delta \ell=\mathrm{m} \omega^{2}\left(\ell_{0}+\Delta \ell\right)\)

\(\Delta \ell=\frac{m \omega^{2} \ell_{0}}{k-m \omega^{2}} \approx \frac{m \omega \ell_{0}}{k}\)

\(\frac{\Delta \ell}{\ell_{0}}=\) Relative change \(=\frac{\mathrm{m} \omega^{2}}{\mathrm{k}}\)