David Alciatore ("Dr. Dave") ILLUSTRATED PRINCIPLES The 30 rule Summary: David Alciatore ("Dr. Dave") ILLUSTRATED PRINCIPLES The 30° rule Part I ­ The Basics Note: Supporting narrated video (NV) demonstrations, high-speed video (HSV) clips, and technical proofs (TP) can be accessed and viewed online at billiards.colostate.edu. The reference numbers used in the article (e.g., NV 3.8) help you locate the resources on the website. If you don't know the 30º rule yet, learning it can truly transform your game. Like the 90º rule, presented in my previous series of three articles, the 30º rule helps you predict the path of the cue ball after impact with an object ball. This is a very important skill to have for helping you prevent scratches, plan break-up and avoidance shots, and execute carom and billiards shots. It is also critical in being able to play position (the skill that separates the great players from the good ones). It always surprises me how few people know this rule. Also, it is shocking to me that few books on pool and billiards give adequate (or any) coverage of this principle. As shown in my previous three articles, the tangent line and the 90° rule are useful for predicting the path of the cue ball when it strikes an object ball with no topspin or bottom spin (i.e., for stun shots). However, with many shots the cue ball is rolling (with topspin) by the time it strikes the object ball. So for many shots, the angle between the cue ball and the object ball will be less than 90°. A useful rule for predicting the path of the cue ball when it is rolling is the 30° rule presented in Principle 2 and Diagram 1. It states that if the cue ball hits approximately half Collections: Engineering