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A block of mass 0 . 1 kg is attached to a cord passing through a hole in a horizontal frictionless horizontal surface as shown in the figure. The block is originally revolving at a distance of 0 . 4 m from the hole, with an angular velocity of 2 rad s - 1 . The cord is then pulled from below, shortening the radius of the circle in which the block revolves to 0 . 2 m . Considering the block to be point mass, calculate

Correct answer

8

Step-by-step solution

By conservation of angular momentum I 1 ω 1 = I 2 ω 2 ⇒       M R 1 2 ω 1 = M R 2 2 ω 2 ⇒       ω 2 = R 1 R 2 2 ω 1 = 0 .4 0 .2 2 × 2 = 8   rad   s - 1

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