A light solid sphere of radius r is placed on top of a heavy hemisphere of radius 5r. A small mass m is embedded into the sphere a distance (2r/3) from the center. Initially, the mass is located directly below the center of the sphere. Find the period of small-amplitude oscillations of the sphere. Assume that there is no slipping, and the hemisphere is not moving.

We received a very healthy number of solutions to our October Challenge, Ups and more ups. It is our hope that the teachers will continue to encourage their students to send us their solutions. As always, we would also love to see more reader-contributed Challenges.

We are pleased to recognize the following successful solvers:

  • Philip Blanco (Grossmont College, El Cajon, CA)

  • Phil Cahill (The SI Organization, Inc., Rosemont, PA)

  • Norman Derby (Southwestern Oregon Community College, Brookings, OR)

  • Don...

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