$\left(\frac{\mathrm{d} \theta}{\mathrm{dt}}\right)=\frac{\sigma \mathrm{e} \mathrm{A}}{\mathrm{ms}}\left(\theta^{4}-\theta_{\mathrm{s}}^{4}\right)$
since mass of hollow sphere is less its $\frac{\mathrm{d} \theta}{\mathrm{dt}}$ is more
Hollow sphere. Cools faster


