Summary: David Alciatore ("Dr. Dave") ILLUSTRATED PRINCIPLES
"Throw Part I: introduction"
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 help you locate the resources on the website. If you
have a slow or inconvenient Internet connection, you might want to view the resources
from a CD-ROM. See the website for details.
This is the first of a series of articles I plan to write concerning "throw" effects. If you don't yet
know about "throw" and the effects of speed, cut angle, and English, you are probably missing
some shots that you might think you should make, and you are probably not able to make some
shots you might see others make. First, let's start out with some terminology and definitions.
Throw is the change in object ball (OB) direction due to sliding friction forces between the cue
ball (CB) and OB during impact. The sliding friction force results from relative motion between
the CB and OB caused by English or cut angle. Diagram 1 illustrates spin-induced throw (SIT)
caused by English. In this case, the right English causes sliding friction during impact that
pushes the OB to the left. Left English would have the opposite effect ... it would throw the OB to
sideways throwing force
due to spin and friction
thrown OB motion