Q38 / 51 · JEE Advanced 2023 (Paper 1) · Physics
A bar of mass and length is lying on a horizontal frictionless surface. One end of the bar is pivoted at a point about which it is free to rotate. A small mass is moving on the same horizontal surface with speed on a path perpendicular to the bar. It hits the bar at a distance from the pivoted end and returns back on the same path with speed . After this elastic collision, the bar rotates with an angular velocity . Which of the following statement is correct?
- Correct answerAand
- Band
- Cand
- Dand
Solution
Before:
After:
Applying conservation of angular momentum about point , we get
As the collision is elastic,
Using equation and , we can write
Given: and
Therefore,
Now,
Hence, the correct answer is option: 'A'.

