A person of mass 76kg stands at the center of a rotating merry-go-round platform

Question

A person of mass 76kg stands at the center of a rotating merry-go-round platform of radius 3.1m and moment of inertia 890kgm2/s . The platform rotates without friction with angular velocity 0.85rad/s . The person walks radially to the edge of the platform.

A: (Already did this part and got it right; only need part B but answer for part A is used in part B, I think) Calculate the angular velocity when the person reaches the edge. ANSWER IS w=.4669 rad/s.

B: Calculate the rotational kinetic energy of the system of platform plus person before and after the person's walk.

Explanation / Answer

B) KE before = 1/2 I w^2 = 0.5*890*0.85^2=321.5 J

KE after = 1/2 I total w^2 = 1/2 (I + mr^2) w^2 = 0.5*(890+76*3.1^2)*0.4669^2=176.6 J

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