By Peter Weiss
Bouncing rocks across the local pond may be the epitome of casual amusement, but that’s no reason not to use a bit of physics to improve your technique.
To achieve controllable, repeatable tosses in the laboratory, Christophe Clanet of the Institut de Recherché sur les Phénomènes Hors Équilibre in Marseille, France, and his colleagues devised an electric-powered catapult that hurled spinning, cookie-size model stones–actually aluminum disks–into a vat of water as long as a bathtub. The experiment focused on the stones’ initial impact with the water.