Billiards TheoryPushing off line = Deflection = Squirt
Squirt is the initial cue ball deflection due to side, in effect the push-off. When right side is imparted, the cue ball will push away left, and vice versa.
Furthermore, the cue ball will jump (when played with any significant strength) when using top or bottom, and this is because of the squirt in the vertical plane. A deep screw-shot immediately lifts the cue ball whereas heavy top bounces it into the bed first.
The reason a ball squirts is due to the conservation of momentum. For example, when right side is imparted the tip end part of the cue is pushed to the right side as the cue pushes through the shot.
Some simple Maths
Conservation of momentum states that M1 x V1 = M2 x V2, where:
M1 is the mass of the cue ball
V1 is the sideways velocity of the cue ball
M2 is the mass of the last few inches of the cue (at the tip end)
V2 is the sideways velocity of the last few inches of the cue (at the tip end)
What this means
Therefore, the heavier the tip end of the cue, the more the cue ball will squirt. In practical terms this means that every cue has a different feel and the player has to get used to the squirt. If you swap your cue, or perhaps alter the mass of the tip end by cutting a few inches off that end and therefore making it thicker, (adding more length to the butt to compensate) you will initially have difficulty adjusting the aim of the shot when playing with side. Interestingly, some American Pool Cues have been manufactured to minimize the mass in the tip end of the cue in order to make shots with side easier to judge - the tip end of the cue is hollow.
The strength of the shot, elevation of the cue and the cloth have very little effect on the squirt; it is purely down to the cue itself.