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When a shooter is shooting at a legal object ball that is close to a non-legal object ball, there is the potential for the shooter to foul by hitting the non-legal ball first. Often, the players will disagree on whether or not the shooter fouled. In these situations, it is best for the opponent to call a referee to observe the shot. If the players often disagree, how can the referee be sure he is making the correct call? If the shooter shoots hard and the balls move fast, how can the referee tell what happened? BCA referees are trained in the physics of ball collisions. Physics determine the path of the cue ball when the balls collide. The path of the cue ball clearly shows which ball was hit first, and this is what the referee is watching. Prior to the shot, the referee will judge the distance between the two object balls to determine which of two possible paths the cue ball will take. If the distance between the two balls is less than the diameter of a quarter, the cue ball will move away from the object ball that was hit first. After the collision with the object ball, the edge of the cue ball will travel along the tangent line between the cue ball and the object ball. In Diagram 1, the cue ball then travels towards the left along the tangent line until it hits the other object ball. After this second collision, the cue ball will continue towards the left. If the object ball on the left were hit first, the cue ball would travel toward the right. The best position to view the shot is from behind the shooter, directly in line with the shooters line of aim. From this position, it is easy to see even slight movement of the cue ball to the left or right.
If the distance between the object balls is greater than the diameter of a quarter, the cue ball takes a different path. In this case, the cue ball initially reacts the same as the previous situation. If the object ball on the right is hit first, the cue ball initially travels down the tangent line to the left. When it contacts the second object ball, the cue ball begins traveling down the second tangent line that is between the second object ball and the cue ball. Because the cue ball hits the second object ball on it's right side, the path of the cue ball changes direction towards the right (see diagram 2). The best position to view this shot is from behind the shooter, directly in line with the shooters line of aim.
Speed is not a factor in the cue balls path when the object balls a close together. If the shooter shot with follow, the cue ball will still move left or right as described, but will move farther away from the shooter. If draw was used, the cue ball will move closer to the shooter, but it will still be moving left or right as described. When the distance between the object balls is close to the diameter of a quarter, it may be difficult to determine which ball was hit first. If the referee cannot determine which ball was hit first, BCA rule 1.16.4 is applied. It states “If the cue ball strikes a legal object ball and a non-legal object ball at approximately the same instant, and it cannot be determined which ball was hit first, the judgment will go in favor of the shooter”. |
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