How do you find the moment of inertia for a person? There was a demo where a per

Question

How do you find the moment of inertia for a person?

There was a demo where a person stood on a spinning platform (with little resistance), and was holding weights. They put their arms out and were spun, and then brought in their arms, which increased the velocity of spin. The mass of the person was 55kg, the weights combined were 5kg. 

Height of person was 168 cm

Radius with arms extended: 30 cm

Radius with arms in (center of mass to shoulder): 13 cm

Mass of platform: 10 kg

Period with arms extended: 1.3s,

Period with arms in: 1.1 s

Probably way too much information in here, I just don't know how to begin.

Instructions stated to treat the person as a rigid body, not a geometric shape

 

Explanation / Answer

Try considering the person as a point mass: I = mr^2

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