David's Tip of the Week 7.13.07

Over the course of the next few weeks, I'm going to discuss some basic techniques to aid in position play, banking, and kicking. Before we get deep into those topics, I'd like to cover a very basic method for determining the path of the CB, known as the tangent line.

In mathematics, a tangent line for a circle is a line which crosses the circle at one point and one point only . That line is always at a right angle to the radius of the circle. In pool, a tangent line forms a right angle to the path of the OB. In this diagram, if the 1-ball is being shot in the side (yellow line), the red line represents the tangent line. The CB, if shot so that it is not spinning when it contacts the OB, will more or less follow this line. In the diagram, if the CB is to the left of the line of the shot, the CB must travel to the right down the tangent line, and vice versa.
There can be a slight deviation because of friction, inelasticity, etc., but for most purposes, the deviation is slight enough to be ignored.

The tangent line forms the basis for all position play. In an earlier tip, I talked about being on the "right side" of the shot. Calculating the tangent line is done to help determine the right side of the shot.

To calculate the tangent line on a pool table, use your cue as a guide. Face the OB so that you are in line with the OB and pocket. In the diagram, that means I'd be standing by the bottom side pocket. Take your cue so the the shaft is in one hand, the butt in the other, and place the cue so that it makes a right angle to the line from OB to pocket. In this example, that will be the red line. After getting used to making conscious calculations for the tangent line, the calculation will become second nature and part of the playing routine.

Ball speed is very important, in conjunction with the tangent line. The harder the CB is struck, the farther down the tangent line the CB will go, assuming there is a cut angle. If there is no cut angle (a straight-in shot), all the momentum from the CB is transferred to the OB, and the CB simply stops. Because of this conservation of momentum, the fuller the hit (straighter the shot), the harder the CB must be hit in order to send the CB farther down the tangent line. The thinner the hit, the easier it is to send the CB down the tangent line. When playing position, take these facts into account. If the CB only requires a few inches of travel off an OB, don't set up a tough cut shot, set up a fairly straight-in shot. The opposite of that applies when you need the CB to do some traveling - don't set up a straight-in shot, set up a cut shot.

I often am the coach for timeouts - here's a typical one:
Player: "TIMEOUT!"
Me: "You're supposed to call a timeout on the shot BEFORE you get into trouble...."
Player: "Yeah, yeah, just help me now. Am I gonna scratch on this shot?"
Me: I calculate the tangent line, and if the tangent line isn't going to a pocket, I say, "Nope, not as long as you hit center ball and you make the shot."
Player: "What if I don't hit center ball?"
Me: "You'll have to wait until next week to find out...."

What happens if the CB is spinning when it contacts the OB? We'll start to delve into that next week, but as a teaser, go back and read the Tip from 6.28.07 - there are some hints there.

Feel free to post your ideas, comments, and questions about the "Tip of the Week." If you're interested in lessons, please visit http://www.raleighbilliardacademy.com or talk to Steve Lee, Shirley Lee, or me.

-David J. Baranski
doomcue@nc.rr.com