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Two coaxial discs, having moments of inertia I 1 and 2 I 1 , are rotating with respective angular velocities ω 1 and 2 1 ω , about their common axis. They are brought in contact with each other and thereafter they rotate with a common angular velocity. If E f and E i are the final and initial total energies, then (E f –E i ) is :

1. 6 I 2 1 1 ω
2. 2 1 1 I 8 3 ω
3. – 12 I 2 1 1 ω
4. – 24 I 2 1 1 ω

Correct answer: – 24 I 2 1 1 ω

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