It allows students to prove to themselves that a ball dropped straight to the floor and one shot outward will hit the ground at the same time. Student keeps both steel balls in position on the base and propels them at the same instant using the spring plunger. Comprises a spring loaded steel launcher mounted in brackets on a metal base. Also includes one solid steel sphere and one steel sphere with a hole to slide it into the launcher. Complete with a rod mounted on the base for fixing the apparatus on a suitable retort stand. Spring compressed by the handle can be locked into two different positions corresponding to two potential energy levels. Once spring is compressed, both the spheres can be located at their respective places. On releasing the handle, the launcher imparts horizontal velocity to the solid sphere while the other sphere simply falls vertically. Falling of both the spheres on the ground implies that vertical and horizontal velocities are independent.