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Question: Answered & Verified by Expert
A bar of mass m and length l is in pure translational motion with its centre of mass moving with a velocity v. It collides and sticks to another identical bar at rest as shown in the figure. Assuming that after the collision the system of the two bars becomes one composite bar of length 2l, then the angular velocity of the composite bar will be

PhysicsRotational MotionJEE Main
Options:
  • A 3 v 4 l , anti-clockwise
  • B 4 v 3 l , anti-clockwise
  • C 3 v 4 l , clockwise
  • D 4 v 3 l , clockwise
Solution:
2645 Upvotes Verified Answer
The correct answer is: 3 v 4 l , anti-clockwise
By law of conservation of angular momentum

        Σ mvr = I system ω

⇒     mv l 2 = 2 m 2 l 2 1 2 ω = 2 m 4 l 2 1 2 ω

⇒         ω = 3 v 4 l anti-clockwise

Note that clockwise or anti-clockwise rotation can only be determined here by the given diagram.

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