This apparatus is designed specifically to show the complex concept that a body impelled horizontally will fall vertically at the same rate as a similar body allowed to fall freely. Comprises a spring loaded L section launcher with holes for loading two 19mm diameter steel spheres which act as projectiles. The launcher is released by pushing the trigger which projects one sphere forward while allowing the other to fall freely. Mounted on a wooden block L23 x W14 x D6cm with storage pocket for the spheres. The unit is supplied complete with the steel spheres.