A car, starting from rest, accelerates at a rate of $\beta$ through a distance S , then continues at constant speed for time t and then decelerates at a rate of $\frac{\beta}{2}$ to come to rest. If the total distance travelled is $10 S$, then ratio $\frac{S}{t^2}$ is

From the same point, two stones A and B are thrown simultaneously, A is thrown up vertically with a velocity of $10 \mathrm{~ms}^{-1}$ and $B$ is thrown up with the same velocity at $30^{\circ}$ with the horizontal. The separation between the balls at 2 s is