\( = \sqrt {\frac{{2G}}{R}\frac{{4\pi {R^3}}}{3}\rho } = - R\sqrt {\frac{{8\pi G}}{3}\rho } \)
\(\therefore \frac{{{v_e}}}{{{v_p}}} = \frac{{{R_e}}}{{{R_p}}} \times \sqrt {\frac{{{\rho _e}}}{{{\rho _p}}}} = \frac{1}{2} \times \sqrt {\frac{1}{2}} = \frac{1}{{\underline {2\sqrt 2 } }}\)
\(\left( {{R_p} = 2{R_e}and\,{\rho _p} = 2{\rho _e}} \right)\)