physics question

Question

A person bending forward at the waist has a momentum of inertia of 6.05 kg·m² relative to an axis of rotation placed underneath their feet. When that person is standing straight up, their moment of inertia is 2.72 kg·m² relative to the same axis. If a person bending forward while standing on a rotating platform has an angular velocity of 0.34 rad/s, what is their angular velocity when they return to a vertical standing position? 

Answer 1

Apply Conservation of Energy

Gravitation Potential Energy is Zero, since there is no change of elevation during motion..

KE1 = KE2

(1/2) * I1 * w1^2 = (1/2) * I2 * w2^2

w2 = ((I1/I2) * w1^2 )^1/2

w2 = 0.5 rad/s