A student sitting on a frictionless rotating stool has rotational inertia 0.96 k

Question

A student sitting on a frictionless rotating stool has rotational inertia 0.96 kg.m^2 about a vertical axis through her center of mass when her arms are tight to her chest. The stool rotates at 7.35 rad/s and has negligible mass. The student extends her arms until her hands, each holding a 4.6 kg mass, are 0.77 m from the rotation axis.
a. Ignoring her arm mass, what's her new rotational velocity?
b. Repeat if each arm is modeled as a 0.77 m long uniform rod of mass of 4.6 kg and her total body mass is 55kg

Explanation / Answer

This is related to the conservation of angular momentum.
I11 = I22

I1=0.96   1=7.35 I2=0.96+(9.2*0.77^2) =6.41

2=1.1rad/sec

Inthe second case I2 = 0.96 + (9.2*.385^2) = 2.32

2 = 3.03 rad/sec

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