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In a playground there is a merry-go-round of mass 120 kg and radius 4 m. The radius of gyration is 3m. A child of mass 30 kg runs at a speed of 5 m/sec tangent to the rim of the merry-go-round when it is at rest and then jumps on it. Neglect friction and find the angular velocity of the merry-go-round and child

a. 0.2 rad/sec
b. 0.1 rad/sec
c. 0.4 rad/sec
d. 0.8 rad/sec

1 Answer

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Final answer:

The angular velocity of the merry-go-round after the child jumps onto it can be found by using the principle of conservation of angular momentum, considering the mass and initial speed of the child, the mass and radius of gyration of the merry-go-round.

Step-by-step explanation:

The student is asking about finding the angular velocity of a merry-go-round after a child jumps onto it, a problem that can be solved using the concepts of conservation of angular momentum and the moment of inertia.

Initially, the child is running with a linear momentum m * v, which when jumping onto the merry-go-round, becomes angular momentum since the child will have a circular motion about the axis of rotation. The radius of gyration is crucial as it allows us to treat the merry-go-round as if all its mass were concentrated at that radius for calculating the moment of inertia.

To solve the problem we would set the initial angular momentum equal to the final angular momentum. The computations involve the mass of the merry-go-round, the mass of the child, the radius, the radius of gyration, and the velocity of the child just before they jump on the merry-go-round. The answer would be one of the angular velocity options provided (0.2, 0.1, 0.4, or 0.8 rad/s).

SUMUP: To find the angular velocity, we apply conservation of angular momentum before and after the child jumps onto the merry-go-round. As the exact values are not given in the question, this is a conceptual answer.

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