The Visible Variable Inertia Set is a wonderfully simple tool for students to explore the relationship between mass and radius in rotational dynamics. The set includes two identical clear disks, each with eight wells for inserting steel spheres. This allows students to easily change the rotational inertia of the disks by simply rearranging the spheres in the wells.

 One key to this set is simplicity. Students can quickly and easily change the orientation of the spheres by pulling apart the two halves of each disk, rearranging the spheres, and then snapping the disk back together. This hands-on approach allows students to physically manipulate the disks and spheres, giving them a more intuitive understanding of the concepts involved.

 Another key feature of the Visible Variable Inertia Set is its visual aspect. The steel spheres in the wells provide a clear and visible representation of the relationship between mass and radius. As students change the arrangement of the spheres, they can see firsthand how the rotational inertia of the disk is affected. This visual component is particularly useful for students who may struggle with abstract concepts, as it allows them to see the direct relationship between the physical properties of the spheres and the rotational dynamics of the disk.