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Billiards Digest June, 2009 David Alciatore, PhD ("Dr. Dave") ILLUSTRATED PRINCIPLES

Summary: Billiards Digest June, 2009
David Alciatore, PhD ("Dr. Dave") ILLUSTRATED PRINCIPLES
"Draw Shot Physics - Part III: spin ratio"
Note: Supporting narrated video (NV) demonstrations, high-speed video (HSV) clips, and
technical proofs (TP), and all of my past articles, 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 or DVD. Details can be found online
at: dr-dave-billiards.com.
This is the third article in a series on draw shot physics. In the previous two months, we
looked at the basics, listed a set of conclusions from a physics analysis (TP B.8), and looked at
some practical examples where the conclusions are useful. With a straight-on (0 cut angle) draw
shot, the draw distance is determined solely by the amount of spin the cue ball (CB) has when it
hits the object ball (OB). Last month, we looked at how the CB's spin changes due to "drag" on
the way to the OB. Clear demonstrations of this can be viewed in HSV 3.1 and NV B.10. For a
draw shots with a cut angle (i.e., not straight in), both the speed and spin on the CB are important
factors. With some shots, it is important to have a lot of CB spin but not too much forward speed
to get the best result (e.g., position for the next shot). When the CB has lots of spin and less
speed, it is said to have a high spin-to-speed ratio, which is the focus of this month's article.
technical proof


Source: Alciatore, David G. - Department of Mechanical Engineering, Colorado State University


Collections: Engineering