Variable Inertia Apparatus 2/disk 8/ball

Study rotational inertia with this well-conceived lab. 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? Includes two 4-1/2" diameter plastic discs with eight compartments for holding balls; 8 solid steel balls; hardware; instructions. Weight: 16 oz.