A large horizontal circular platform (M=92.6 kg, r=4.23 m) rotates about a frict

Question

A large horizontal circular platform (M=92.6 kg, r=4.23 m) rotates about a frictionless vertical axle. A student (m=69.41 kg) walks slowly from the rim of the platform toward the center. The angular velocity of the system is 3.08 rad/s when the student is at the rim. Find the moment of inertia of platform through the center with respect to the z-axis. Incorrect. Tries 2/5 Previous Tries Find the moment of inertia of the student about the center axis (while standing at the rim) of the platform. Tries 0/5 Find the moment of inertia of the student about the center axis while the student is standing 1.75 m from the center of the platform. Tries 0/5 Find the angular speed when the student is 1.75 m from the center of the platform.

Explanation / Answer

Ip = Mr2/2 = 92.6 x 4.23 x 4.23/2 = 828.44 kgm2

Isi = mr2 = 69.41 x 4.23 x 4.23 = 1241.95 kgm2

Isf = m(1.75)2 = 69.41 x (1.75)2 = 212.57 kgm2

w = 3.08(828.44 + 1241.95)/(828.44 + 212.57) = 6.1256 rad/s

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