Two planets P 1 and P 2 with equal mass have radii R 1 and R 2, respectively, where R 2=R 1/2. The escape speeds of P 1 and P 2 are v 1 and v 2,…

Two planets $\displaystyle \mathrm{P}_1$ and $\displaystyle \mathrm{P}_2$ with equal mass have radii $\displaystyle R_1$ and $\displaystyle R_2$, respectively, where $\displaystyle R_2=\frac{R_1}{2}$. The escape speeds of $\displaystyle \mathrm{P}_1$ and $\displaystyle \mathrm{P}_2$ are $\displaystyle v_1$ and $\displaystyle v_2$, respectively. Then $\displaystyle \frac{v_2}{v_1}$ is :