Postponing the discussion about momentum which was begun in the preceding BQR, in this issue we turn instead to the highly topical subject of kicks - those frustrating occasions when colliding billiard balls fail to separate at the usual angle - the one anticipated from experience and expected on purely mechanical considerations such as momentum. The result of a 'kick' is usually the end of the break, especially for the good player who hits the ball with minimal strength and so is less likely to run on to a fluke. Because the departure from normal behaviour is generally very marked, the sense of being cheated is correspondingly sharp. Peter Gilchrist, whose departure from this year's World Billiards in the semi final was occasioned by just such an event, will doubtless confirm this. What was intended to be a gentle cannon with side off the top cushion onto the white turned out to be the end of a break of 301 and so of a chance to run out against Russell. The latter player confessed to his relief at being so let off in a very tight finish.
Although kicks must be as old as the game of billiards (according to Riso Levi, they occurred with ivories), there does not seem to be any consensus as to what causes them. A careful investigation seems first to have been made by Riso and was reported in The Billiard Player in 1924 (and also in volume II of Billiards for the Million) and is worth summarising. He found (a) that chalking the ball over the impact area nearly always resulted in a 'kick' occurring; (b) that when a 'kick' occurred, the result was that the cue ball was deflected through a wider angle than usual, (c) that sticking a piece of paper over the impact area of the object ball caused the angle of deflection to be narrower. He also claimed that certain sets of balls were more prone to kick than others.
So what causes these annoying incidents? Is it simply the presence of chalk on one of the balls coming between the two impacting bails, or is there some other factor, possibly one operates only when the chalk is there? Is static electricity the cause? Or is some detail of the fabrication of the ball relevant? To the scientists at The Academy of Quantitative Billiards it seems that there is insufficient data on the subject to allow conclusions to be drawn. Therefore, we are asking our readers, who between them must have had many hundreds of 'kicks', to write in with their experiences. To set the ball rolling (as it were!) here is one which nearly cost BJC his league match the other week. He was playing a long 'drop' cannon from white onto the red but kicked on the white. The cue ball passed in front of the red, having been deflected through a wider angle than intended. The balls were Super Crystalates; the cloth was neither new nor old; chalk was blue National Tournament. The floor was carpet tiled (presumably synthetic fibres). The lighting was by fluorescent tube. Readers are invited to report the circumstances accompanying their own 'kicks', including such detail as they may think relevant.