Playing Pool June 8, 2015

billiardsDid you know billiards was a French game?  Neither did I.  I find that pool is a very interesting game that can be extremely rewarding but also incredibly frustrating.  It just depends on the day, or even the phase of the moon.  When I play pool, I never know what I’m going to get.  I stumbled across this article detailing some of the intricacies of the pool game that you might find interesting:

“Physics helps, of course. But the difference between a phsyicist and a billiard player is the difference between theory and practice. Newton played with idealized balls under idealized conditions. A billiard player has to worry about things like the nap of the cloth, the resiliency of the rails, and thanks to Mingaud, the application of spin on the cue ball.

When the cue ball h its another ball straight on, it transfers all of its momentum to the other ball, called the object ball, which takes off in the same direction the cue ball was headed. If the cue balls hits the object ball off-centeR, then only part of its momentum is transferred, and the two balls take off roughly at right angles to each other.

This would make things simple excet for a phenomenon called throws. If the cue ball is hit to the right or left of center–giving it English–it will throw the object ball a little in the direction of the spin before sending it on its way. Throw also occurs when two object balls are touching–“frozen” in pool hall parlance. The friction between the two balls causes th eball being ht to drag the other for a short distance before they begin to roll. “When frozen balls are hit,” says Byrne, “they behave for an instant as though they are one ball.”

But hitting the balls is only prt of the game. “It’s cross between chess and golf,” says Harry Sims, currently the United States three-cushion billiard champion. “It takes a three-dimensional mind: You have to make the shot, get into a position to make another shot, and make sure that if you miss, you don’t leave your opponent with an easy shot.” It’s the latter two tasks that make Mingaud’s work Promethean. Prior to the Frenchman’s leatherwork, a cue ball hit another ball and then rolleth where it listeth. Thanks to spin the cue ball rolleth where the player listeth it.

For example, suppose a pool player wanted to knock in a ball resting near a corner pocket but also leave the cue ball in position to sink a ball lying near a side rail. An expert player can sink the first ball and still set up the net shot by hitting the cue ball below center and hard, giving it backspin. The spinning cue ball skids along the felt until it hits–and sinks–the object ball. Because the balls are together only an instant, there is little friction between them, and the cue ball continues to spin after the collision. The backwards spin makes it roll backwards–to an ideal position to sink the next ball. Expert players can give the cue ball so much backspin it travels the length of the table twice. Similarly, a player can give the cue ball top spin and csue it to roll forward or “follow” after it hits an object ball. Side English can make the ball ricochet off the rals at a greater or smaller angle.

Sometimes side English can be created mid-shot. When a cue ball with top or backspin hits an object ball obliquely, the ball’s spin maintains its original orientation even though it caroms off at an angle. Thus stop or backspin off at an angle. Thus top or backspin suddenly becomes sidespin, which curves the cue ball’s path. Top spin will make the cue ball curve toward the ball it just hit; backspin makes it curve away.

The ultimate in curving English is the masse shot. The masse was used, no doubt, to make Mingaud’s cue ball do its Gallic hat dance. It is also used, rarely, in regular play when the only available shot to an object ball involves giving the cue ball so much spin it curves around another ball.

An alternative to going around a ball is jumping over it. Hitting the cue ball very low and hoisting it in the air is illegal, as well as frowned upon by whoever might have to pay for the ripped felt. But a ball hit with enough downward force at about a 45-degree angle–a legal shot–will leave the table. The trick, of course, is to make it come down in front of the object ball and not in front of grandma’s antique vase.

The masse and jump shots are reserved mainly for show. But the real art of shooting billiards comes in three cushion, a game that is played all over the world. Billiards uses one cue ball and two object balls. To score a point a player has to hit one of the object balls and three or more rails before hitting the second object ball. Consequently, a single shot can take several seconds as the ball caroms around the table. The shots are often so precise that the nap in the felt, which usually runs lengthwise on the table, has to be taken into consideration because it can make the ball slowly curve.

Five points in a row is considered a good turn, and few masters have scored more than 20. The complexity of the game gives rise to different styles of play. Latin American players tend to concentrate on making the shot at hand, Americans stress preventing easy shots for the opponent, and Europeans are fond of setting the balls in favorable positions to string several points in a row.”

Allman, William F. “Pool hall physics.” Science ’84 5 (1984): 100+. Academic OneFile. Web. 7 June 2015.

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