Have you ever had an easy cut shot that you shot a little hard without english and missed the pocket by a couple inches or more. You probably attributed the miss to your stroke, eye alignment or a myriad of other things. The chances are though your aim and stroke were dead on. The probable reason for your miss was object ball deflection*. Huh? You say you're an advanced player and know all about cue ball deflection which occurs when you strike the cue ball hard enough using english but how can the object ball deflect without any english being applied? The answer is that the same principle applies to both object ball and cue ball deflection. It is not the english being applied that causes the deflection but rather that the contact point on the ball being hit is off center. When a cue ball is hit off center with the tip of a cue stick both the cue and stick will deflect away from each other off the line of aim. The same is true when a ball contacts another ball off center if the speed is sufficient. Both balls will deflect away from each other. The harder you hit the greater the deflection off the line of aim. Object ball deflection will occur at a lower speed than cue ball deflection. The reason for this is that with cue ball deflection you have chalk applied to the tip of the cue which keeps the cue tip on the cue ball longer. With object ball deflection you have 2 polished balls colliding with each other both of which deflect right away.
Below the 15 ball is shot into the corner with soft to medium speed. The line of aim from the cue ball to the object ball is dead on to the point of contact made by a line running from the center of the pocket through the center of the object ball. In this case there is little or no object ball deflection.
Diagram 1
