Please help and explain your reasoning clearly NT8F-CCT39: CHILD ON ROTATING PLA

Question

Please help and explain your reasoning clearly NT8F-CCT39: CHILD ON ROTATING PLATFORM-FINAL ANGULAR VELOcITY A very low friction merry-go-round (rotating platform) with a radius of 1.5 m and moment of inertia of 50 kg m s rotating at 100 rev/min. A child with a mass of 20 kg initially sits 1 m from the center, and then moves outward toward the edge of the platform. Two students are discussing how to calculate the final angular velocity of the platform: Arno: "I think we have to use conservation of angular momentum. The distance from the child to the axis of rotation increases, so her moment of inertia increases. The total moment ofinertia goes up, and so the angular velocity has to go down." Belle: "Well, I agree that the angular velocity goes down, but I think you are going to get the wrong value. We need to use collision here. conservation of energy instead of conservation of momentum, because there is no of inertia kinetic energy is what's to stay same and the moment increases, the angular velocity goes down." which, if any, of these students do you agree with and think is correct? Belle Neither Arno Please explain your reasoning

Explanation / Answer

Answer of CCT39

Statement of Arno is correct.

According to Belle, rotational kinetic energy of system will remain the same, but actually this is not the case. Energy of the system will be disturbed due to the movement of child, however angular momentum of system will remain the same in any condition.
Therefore, angular velocity will be calculated by using conservation of angular momentum principle.

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