A horizontal platform in the shape of a uniform circular disk rotates on a frictionless bearing about a vertical axle through the center of the disk. The platform has a mass of 150 kg, and radius of 2.00 m. A 60kg student walks slowly from the rim of the platform toward the center. If the angular speed of the system is 1.5 rad/s when the student starts walking, what is the angular speed when she is 0.50 m from the center?(adsbygoogle = window.adsbygoogle || []).push({});

I originally used the equation Li=Lf

where Li= Iw= (1/2)(MR^2)wi which equals (.5)(210kg)(2.0^2)(1.5rad/s)

Li= 630

Lf= (If1+ If2)(wf)

=[(.5)(150)(2.0^2) + (60)(0.5^2)]wf

This gave me wf= 2.0 rad/s but that doesn't seem to make sense wouldn't the angular speed slow down as the student went closer to the center? Any hints as to where I went wrong is greatly appreciated.

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# Homework Help: Circular disk rotates with student on it

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