Question

Example: The bob $A$ of a pendulum released from ${30}^{\circ }$ to the vertical hits another bob $B$ of the same mass at rest on table as shown in figure. How high does the bob $A$ rise after the collision? Neglect the size of the bob and assume the collision to be elastic.

• A. $L-\frac{L\sqrt{3}}{2}$
• B. $L-\frac{L}{2}$
• C. zero
• D. $L-L\sqrt{\frac{2}{3}}$

Answer 1

The correct option is C

zero

The two bobs $A$ and $B$ are of the same mass and the collision between them is elastic. Thus, after collision, the two bobs will interchange their velocities. Obviously, the bob $A$ would come to rest and does not rise at all. But bob $B$ would move with the velocity of $A$.