The terminal velocity is given by v, where v α r2 (r = radius of the sphere). The mass of the sphere can be given by
\( m = \frac{4}{2} \pi r^3\rho, thus\,m \propto r^3
\)
\(\frac{m_1}{m_2} = \frac{1}{8}=( \frac{r_1}{r_2})^3 \,\,\Rightarrow\frac{r_1}{r_2} = \frac{1}{2}\)
\( and \, since, \frac{v_1}{v_2} = (\frac{r_1}{r_2})^2 = \frac{1}{4}\)
\( \Rightarrow\frac{v}{nv} = \frac{1}{4}\)
\( \Rightarrow n=4\)