cut shot

• back cut
• ball-hit fraction vs. cut angle
• margin for error
• speeds and travel distances for the CB and OB

For more information, see Disc I of the Video Encyclopedia of Pool Shots

back cut

What is a back cut and why is it tougher than a regular cut?

A back cut is a cut shot where the cue ball is shot well away from the target pocket (e.g., when the cue ball is much closer to the target pocket rail than the object ball). These shots can be more difficult than cut shots looking toward a pocket because the required cut angle can appear larger than it actually is, because you are looking away from the pocket. As a result, most people tend to overcut back cuts (i.e., they are hit too thin).

from Patrick Johnson:

When we shoot back cuts we're looking away from some important visual cues, namely the pocket and the rails that point to it. We learned to use these cues to help us see the OB-to-pocket line and find the contact point/cut angle without all the walking around (the usual reason for innovation). But we learned them subliminally, so we don't notice that we're using them and don't know what's wrong when they're gone.

Once we do know what's wrong, the simple solution is obvious: revert to walking around and sighting the OB-to-pocket line as we did before learning to use the visual cues (or resort to the stick-pivot method or any other "mechanical" method to get a fix on the contact point/cut angle).

ball-hit fraction vs. cut angle

How is cut angle related to ball-hit fraction?

I have illustrations, equations, plots, and numbers on this here:

TP A.23 - Ball-hit fraction vs. cut angle

margin for error

How does the difficulty of a shot vary with cut angle?

The following analysis (which includes several useful graphs) shows how the margin for error varies with both shot distance and cut angle:

TP 3.4 - Margin of error based on distance and cut angle

Also, the effective size of the pocket varies with angle and speed. For more info, see: pocket "size" and "center"

from Bob_Jewett:

An article that discusses how the angle increases the difficulty of a shot (which is to say, decreases the allowed error), is at: http://www.sfbilliards.com/articles/1994-04.pdf The article includes a simple graphical way to see how much the cut angle increases the difficulty over a straight-in shot of the same length.

speed and travel distances for the CB and OB

How do CB and OB speeds and travel distances vary with cut angle?

See my March '09 article. It includes distance graphs for both stun and rolling CB shots.

For more information, see:

http://billiards.colostate.edu/threads/speed.html#balls