“Billiards Mathematically Treated”

Abstract

THE answer to “Enquirer's” puzzle is very simple. If you let a perfectly hard and smooth cue tip impinge at any angle on a perfectly hard and smooth ball, the only force exerted will be normal, and the ball will start in the line from the point of impact to the centre of the ball. At the same time, during the brief duration of the impact the cue tip will slide a minute distance along the surface of the ball, but in consequence of the perfect smoothness will exert no tangential force on the ball.