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As shown below, bob A of a pendulum having massless string of length 'R' is released from 60° to the vertical. It hits another bob B of half the mass that is at rest on a friction less table in the centre. Assuming elastic collision, the magnitude of the velocity of bob A after the collision will be (take g as acceleration due to gravity)

1. 3 1 Rg
2. Rg
3. 3 4 Rg
4. 3 2 Rg

Correct answer: 3 1 Rg

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