13. The platform has a continuous uniform disk shape can rotate by inertia about a stationary vertical axis. On the edge of the platform is a person whose mass is 3 times smaller than the mass of the platform. Determine how and how many times to change the angular velocity of rotation of the platform, if one goes closer to the center by a distance equal to half the radius of the platform.

Detailed solution. Decorated in Microsoft Word 2003. (Target decided to use formula editor)