Variable Inertia Set

This is a unique lab that is simple to set up and illustrates an abstract concept in an easy-to-understand manner. It consists of two plastic discs in two halves (4 halves total) with the same mass and diameter. The discs are hollow inside with injection molded compartments into which balls are inserted in a variety of configurations. You can place the steel balls (19mm ball size) along the rim of the discs, in the center, or in a straight line across, as illustrated. This effectively varies the distribution of mass to become either "center heavy" or "rim heavy." Quickly change the distribution of mass by loading balls in compartments inside two plastic discs. Which is faster - the disc with the mass toward the center or toward the rim? Why? Please note: The Inclined Plane is sold separately.