Question

Two identical balls $A$ and $B$ are released from the positions shown in the figure. They collide elastically on horizontal portion $MN$. The ratio of heights attained by $A$ and $B$ after collision will be (neglect friction)

• A. $1 : 4$
• B. $2 : 1$
• C. $4 : 13$
• D. $2 : 11$

Answer 1

Answer: (C)

$4 : 13$

Answer 2

After collision balls exchange their velocities i.e., $v_{A} = \sqrt{2\,gh}$ and $v_{B} = \sqrt{2g\left(4h\right)} = 2\sqrt{2gh}$ Height attained by $A$ will be $h_{A} = \frac{v^{2}A}{2g} = h$