Summary: David Alciatore, PhD ("Dr. Dave") ILLUSTRATED PRINCIPLES
"Coriolis was brilliant ... but he didn't have a high-speed camera
Part IV: maximum cue tip offset"
Note: Supporting narrated video (NV) demonstrations, high-speed video (HSV) clips, and
technical proofs (TP) can be accessed and viewed online at billiards.colostate.edu. The
reference numbers used in the article (e.g., HSV A.16) help you locate the resources on the
This is the fourth article in a series I am writing about the pool physics book written in 1835 by
the famous mathematician and physicists Coriolis. Two months ago, I described some high-
speed camera work I've done and showed some examples that relate to some of Coriolis'
conclusions. Last month's article dealt with the shape of the cue ball's path after hitting an object
ball, and the effect of spin and speed on the shape of the path. FYI, all of my past articles can be
viewed on my website in the instructional articles section.
The topic of this article is Coriolis' conclusion summarized in Principle 24. He claims that to
achieve maximum English, the cue tip should not contact the cue ball more than half a ball radius
off center, as shown in Diagram 1. For a pool ball, with a diameter of 2 1/4 inches and a radius
of 1 1/8 inches, the corresponding contact point would be off center by 9/16 of an inch. It just so
happens that the radius of the red circle on an Elephant Practice cue ball (this is the cue ball used
in many of the NV and HSV video clips on my website) happens to be exactly 9/16 of an inch.
The reason for this is that hitting the cue ball with offsets much larger than this creates a high risk