Q 11-05-141JEE MainJEE Main 2021 (24 Feb, Shift 1)Easy
A ball with a speed of $9\ \text{m s}^{-1}$ collides with another identical ball at rest. After the collision, the direction of each ball makes an angle of $30^\circ$ with the original direction. If the ratio of velocities of the balls after the collision is $x : y$, then what is the value of $x$?
Numerical value type. Enter your answer.
Answer: 1
Momentum perpendicular to the original direction is zero before the collision, so after it:
$$mv_1\sin30^\circ = mv_2\sin30^\circ \;\Rightarrow\; v_1 = v_2$$
The ratio is $1 : 1$, so $x = 1$.
Solution by Sreeraj P, M.Sc Physics