Billar, Fundamentos

AN AIMING POINT METHOD FOR POOL Don Smith ddsmjs99@aol.com November, 2009 A method is shown for determining where to aim the cue ball in pool. To use this method, the player must visualize two points on the object ball and the distance between them. It is easy to learn and use, and may be particularly useful for those new to the game. This paper describes the method, called here the “Double TheDistance” method or DTD. A brief description of the DTD is given first below, followed by further detail. SUMMARY OF THE DOUBLE THE DISTANCE METHOD (FIGURE 1) Finding the aiming point is a simple four-step process. Referring to Figure 1, these steps are: 1. Find the point where a line from the cue ball will intersect the object ball. 2. Find the point where a line from the pocket (or other target)will intersect the object ball. 3. Estimate the distance between these two points. 4. Double this distance to find the aiming point. This usually takes 10-20 seconds.

FIGURE 1. FIND THE AIMING POINT IN 4 EASY STEPS INTRODUCTION The discussion and diagrams given here assume a pocket billiards game like 8-ball or 9-ball. The DTD method can, however, be used for any billiards game. There can bepockets or not. The balls can be of any size. The object ball can be directed at any part of a pocket, at a point on the cushion, or at another ball. The cue ball and object ball can be anywhere on the table (with a modification described later, required when the cue and object balls are close together). The aiming point determined by this method does not include the effects of such factors as cueball speed and English. The DTD provides a simple way of making a good first estimate of the aiming point. The effect of other factors must then be taken into account before taking the shot. 1

The rest of this document gives: • A more complete description of the DTD method. • Examples. • The “ghost ball” alternative. • Finding the aiming point when the cue ball and object ball are closetogether. • Using “cue tip widths” for measuring the distance to the aiming point. • The theory on which the Double The Distance method is based. MORE COMPLETE DESCRIPTION OF THE DTD METHOD (FIGURE 2)

FIGURE 2. MORE INFORMATION ABOUT THE DTD Step 1 of the DTD method, displayed in Figure 2, is to imagine a line from the center of the cue ball to the center of the object ball. This is line CO, whichcrosses the object ball at point U. In Step 2, the player visualizes a line from the object ball target, point T, through the center of the object ball O and intersecting the outer edge of the object ball at point N. Point N is also the contact point, where the cue ball must strike the object ball in order to send the object ball to the target. Figure 2 also shows a point S, directly below N, on theline CN from the cue ball. Use of point S simplifies the discussions and figures given here. Step 3 is to visualize line US. The length of US is termed L. Finally, in Step 4, you imagine another line, extending from US and also of length L. The end of this line is the aiming point A. The length of USA (!) is termed D. If the cue ball is now stroked along line CA to the aiming point A, it willstrike the object ball at point N. The object ball will then (we all hope) go into the pocket (or wherever you wished). If it does not, the most common cause is that the length of L was underestimated. It is better to estimate L a little long, thus aiming further away from the object ball. This is equivalent to assuming the cut angle is slightly greater than it appears.

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EXAMPLES (FIGURE 3) InDiagram #1 of Figure 3, the cut angle is 30º. With this cut, the aiming point A, from the player’s perspective, is located very close to the edge of the object ball. This is a fortunate location, since aiming at an edge is easier than aiming at a point inside or outside the object ball. If the cut is greater then 30º, the aiming point will be outside the object ball. Cuts of less than 30º...