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Kutter
12-25-2007, 11:40 AM
Does the 90 degree rule apply also to when either the CB or the OB strikes the rail? Yes, I understand 90 degree has variations, but I am talking about as a general rule, does it apply?

dr_dave
12-25-2007, 12:07 PM
<blockquote><font class="small">Quote Kutter:</font><hr> Does the 90 degree rule apply also to when either the CB or the OB strikes the rail? Yes, I understand 90 degree has variations, but I am talking about as a general rule, does it apply? <hr /></blockquote>The short answer is "no." For the long answer, see the Chapter 6 videos, and NV 4.10 and 4.11 here (http://billiards.colostate.edu/normal_videos/index.html).

Happy Holidays,
Dave

pooltchr
12-25-2007, 01:07 PM
The not quite so short answer is no, because there are other factors that come into play when the ball hits the cushion. Speed of the shot, and spin on the cue ball, condition of the cloth and rubber cushions can all alter the exit angle off the cushion.
Steve

Bob_Jewett
12-26-2007, 01:11 PM
<blockquote><font class="small">Quote Kutter:</font><hr> Does the 90 degree rule apply also to when either the CB or the OB strikes the rail? Yes, I understand 90 degree has variations, but I am talking about as a general rule, does it apply? <hr /></blockquote>
I'm not clear about what you mean here. The 90-degree rule tells you that the angle between the path of the object ball and the path of the cue ball just after contact is a right angle. That's true in nearly all cases and has nothing to do with cushions or pockets. Can you describe a particular shot you are having trouble with?

Kutter
12-27-2007, 12:29 AM
<blockquote><font class="small">Quote Bob_Jewett:</font><hr>That's true in nearly all cases and has nothing to do with cushions or pockets.<hr /></blockquote>
I understood what the 90 degree rule meant. I was asking if it also applied when the CB hit the rail. I now know that it does not apply thanks to Dr Dave's chapter six, which definitely explained it well for me.

Bob_Jewett
12-27-2007, 10:24 AM
<blockquote><font class="small">Quote Kutter:</font><hr> ... I understood what the 90 degree rule meant. I was asking if it also applied when the CB hit the rail. ... <hr /></blockquote>
For cushions it's the mirror reflection rule that covers the simple case -- angle in equals angle out. Of course side spin, draw, follow and to a lesser extent speed all change the outbound angle of a ball from the cushion.

Kutter
12-27-2007, 10:37 AM
Thanks, that's pretty much the idea, I found out.