Billiards Digest October, 2011 "The Lag Shot" ILLUSTRATED PRINCIPLES Summary: Billiards Digest October, 2011 "The Lag Shot" ILLUSTRATED PRINCIPLES David Alciatore, PhD ("Dr. Dave") Supporting narrated video (NV) demonstrations, high-speed video (HSV) clips, and technical proofs (TP), and all of my past articles, can be accessed and viewed online at billiards.colostate.edu. The reference numbers used in my articles will help you locate the resources on the website. If you have a slow or inconvenient Internet connection, you might want to view the resources from a CD-ROM or DVD. Details can be found online at: dr-dave-billiards.com. The topic for this article is the lag shot, which is used to determine who breaks first. Lag shots aren't typically used in league play; but they are often used in tournaments. The winner of the lag has a big advantage in being awarded the first break, especially in a winner-breaks event. Even in alternating-break format, the lag shot can be the determining factor of the match if it goes hill-hill and the winner of the lag gets to break for the deciding game. Last month, we looked at recommended tip contact-point heights for different situations and indicated that the optimal height for consistent speed/distance control is 0.2R, as illustrated in Diagram 1. This is the best tip height to target when shooting a lag shot. Diagram 2 shows why. The graph, which is from the math and physics analysis in TP B.12, shows how cue ball (CB) travel distance varies with tip height, for a given cue speed. With a center-ball hit (point "A"), the cue moves the CB forward initially with the most speed, but the CB slows as it slides (drags) across the cloth and develops forward roll. With a maximum above-center hit (point "C"), at the miscue limit (0.5R), the CB doesn't require drag to develop roll, but the forward speed of the Collections: Engineering