A car is being driven on a road having two distant circular bends $B_1$ and $B_2$ of radius R and 3R respectively. If $S_1$ is the speed of the car at the bend $B_1$ an $S_1$. is the speed at the bend $B_2$, what should the ratio $S_1/S_2$ be so that the centripetal forces at both bands are equal?