A ball in flight

A ball is the main instrument in most outdoor games, and be it football, baseball, cricket, tennis or golf, the common aim is controlled flight in the air. Superficial considerations of the mechanics of a ball in free flight may suggest that the ball describes a simple arc with trajectory in one vertical plane. This rarely happens; it climbs, plunges, swerves laterally and even stalls. It seems to possess a will of its own which defeats most players of all games, yet when exploited by a master of any one of them is a thrill to watch, e.g. an in‐swinging corner‐kick landing in the net, a straight driven golf ball boring into the wind, a cricket ball bowled with late swerve, a tennis ball topping the net and diving to the court, to list but a few. For these things to happen some complex force must act on the ball. This force, since it can come only from the air, is an aerodynamic force. Many learned papers have been written on rotating cylinders and spheres but few of them can be understood by an intelligent layman. It is the purpose of this article to explain in a simple way how this force comes about.