Abstract: An educational apparatus for teaching subject matter relating to mechanics and for demonstrating a number of experiments. The apparatus, in kit form, consists of an assortment of balls of diverse properties, and a pair of upright, parallel, elongate members whose top edges, spaced from one another, provide a track for the balls to roll on. The track has the shape of a double declivity, symmetrically declining from opposite ends toward a center portion which smoothly joins the two slopes. A graduated scale is aligned with the track for the measurements of the distances traveled by the balls. Detents secure the balls at the top of each of the opposite ends of the track and are synchronously retractable by actuation of a remote electrical switch to release the balls simultaneously.