Two uniform circular discs are rotating independently in the same direction around their common axis passing through their centres. The moment of inertia and angular velocity of the first disc are 0 . 1 kg - m 2 and 10 rad s - 1 respectivel

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Two uniform circular discs are rotating independently in the same direction around their common axis passing through their centres. The moment of inertia and angular velocity of the first disc are 0 . 1 kg - m 2 and 10 rad s - 1 respectively while those for the second one are 0 . 2 kg - m 2 and 5 rad s - 1 respectively. At some instant they get stuck together and start rotating as a single system about their common a

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Correct answer: B. 20 3 J

Common angular velocity from angular momentum conversation &#969; = l 1 &#969; 1 + I 2 &#969; 2 I 1 + I 2 = 0 . 1 &#215; 10 + 0 . 2 &#215; 5 0 . 1 + 0 . 2 = 20 3 Final K.E. K f = 1 2 I 1 &#969; 2 + 1 2 I 2 &#969; 2 = 1 2 0 . 1 + 0 . 2 &#215; 20 3 2 &#8658; k f = 20 3

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