Introduction

This article discusses shotmaking techniques used in billiard (billiards) games. In pocket billiards games, proper application of these techniques allow you to set up for successsive shots. This is known as position play. This article is about the various cue sports. ...

Many of these techniques can be combine such as using draw and english on the same shot. This increases the difficulty of correctly making the shot as more variables are being introduced.

Main forces affecting the motion of billiard balls

Billiard balls are simply spheres and obey the laws of physics. But you will see things happen on a billiard table you won't see in many other places for a number of reasons. Billiard balls are smooth and heavy and move along a smooth surface. This allows an unnatural axis of rotation to be imparted to them. Because they are heavy, smooth, and move along a smooth surface, this alternate axis of rotation can be retained for much of its motion. This allows for dramatic results such as being able to move along a curved path, and back up when it hits other balls.

The main forces on a billiard ball are the linear motion of the ball, and its axis of rotation. The axis can be the normal axis of rotation along its linear motion or a different axis of rotation. An axis of rotation other than the normal one can be imparted on a cue by hitting the cue ball above, below, left or right of the center of the ball.

When a cue ball hits a rail, it will normally exit with the same angle it came in with (for a simplistic explanation see the classic movie "Donald in Mathemagics Land.") This is the ideal, but because billliard rails are imperfect this angle will not be exact. When the cue ball has left or right spin on it, this will affect the angle of exit.

When a cue ball hits another ball, its path is naturally tangential to the angle of impact. This angle varies when the cue ball has spin on it. Also the angle the other ball travels after being impacted by the cue ball can be influenced by the spin of the cue ball.

Follow/Draw

If the cue ball is hit sufficiently above or below center, the cue ball, rather than rolling naturally, will have spin along its axis of rotation. If for example, the cue ball is struck above center, overspin can be imparted to the cue ball causing it to spin faster than normal along its axis of rotation. Follow or draw can dramatically alter the normal path the cue ball would follow after striking another ball.

The cue ball has a natural spin along its line of travel, and it will revert to this natural spin no matter how much follow or draw is put onto the cue ball.

Follow

Follow, sometimes called top spin or simply "top," is spin in the direction of travel of the cue ball, such that it is spinning faster than it would from its natural roll. If the cue ball has top spin on it, it will resume rolling forward after making contact dead-on with the object ball and "follow" the object ball rather than stopping abruptly.

Top spin is imparted to a ball by hitting it above the midpoint of its vertical plane as it faces the shooter. Top spin is spin in the direction a ball naturally "wants" to take in reaction to friction from contact with the pool cloth. Because of this, a ball sliding on the cloth will rapidly pick up follow. Likewise, a ball struck so that it is spinning backwards (with draw — see below) immediately starts losing that spin, and if it travels far enough, will reach a sliding point (no spin), soon graduating to natural follow.

Follow applied to a non-dead-on shot will cause the angle of departure of the cue ball from the object ball to widen shortly after impact; the thicker the hit on the object ball, the more this effect will be noticeable (on very thin cut shots it practically does not exist). Similarly, top spin will cause a widening of the cue ball's rebound angle after impact with a rail cushion.

Follow also increases the rate of cue ball travel, both before and after object-ball impact, and actually imparts a small amount of draw to the object ball.

Follow is best applied with a perfectly level cue stick throughout the entire stroke. Many players claim that they try to keep the cue tip on the cue ball to get the maximum follow.

Draw

Draw refers to hitting the cue ball lower than center such that its spin is opposite to its direction of travel. This causes the cue ball to slide rather than roll naturally along the table.

If the cue ball is hit with draw, and if that spin remains on the cue ball at the moment of impact with an object ball, the cue ball will reverse direction on a dead-on or center-to-center hit, and "draw" backwards. Draw is referred to in the United Kingdom as "screw."

Draw applied to a non-dead-on shot will cause the angle of departure of the cue ball from the object ball to narrow shortly after impact. Similarly, it will cause a narrowing of the cue ball's rebound angle after impact with a rail cushion.

Draw also slows the rate of cue ball travel, both before and after object-ball impact, and actually imparts a small amount of follow to the object ball.

Draw is best applied with a slightly elevated cue stick. To get the maximum amount of draw, accelerate through the cue ball and to the cloth with your tip. Players claim that if they try to keep the tip on the cue ball as long as possible, it gives them better draw.

The stop and stun shots

These shots are made by applying the correct amount of draw to the cue ball such that it is sliding when it hits another ball.

When a sliding cue ball contacts an object ball dead-on (a center-to-center hit), the cue ball and object ball are of the same mass, and neither follow nor draw is on the cue ball at the moment of impact, the cue ball will transfer all of its momentum to the object ball and come to a complete stop. If the sliding cue ball in the preceding scenario has sidespin on it when it contacts an object ball dead on, it will come to a complete stop but spin in place at that position until the sidespin dissipates. If the cue ball and object ball contact is not dead-on but still very full, the result will often be a "stun" shot, where the cue ball departs the object ball in the expected direction but travels only a short distance. The stun effect can often be enhanced with a minimal amount of draw, to reduce cue ball speed before impact with the object ball.

English

English (called "side" in the United Kingdom and sometimes simply called "left" or "right") normally refers to sidespin put on a cue ball by hitting it to the left or right of center. Generally, english is used to change the angle of deflection of the cue ball after it contacts a rail. English also affects the direction an object ball takes on impact (the "throw" effect), as well as the path of travel of the cue ball after impact with a cue ("deflection" or "squirt").

Sometimes english is conflated to refer as well to spin imparted on the vertical axis of the cue ball. However, an above center hit is more precisely referred to as "follow," and a below center hit, as "draw." Any time the cue ball is not struck directly in the center, some spin will be imparted, whether left or right english, follow or draw. Unintentional sidespin is a common source of missed shots. Spin is not always placed on the cue ball by the shooter; spin is naturally imparted to the cue ball from contact with pool cloth on the bed of the table and on the table's rails.

Curving the cue ball's path

If both draw and english are applied to the cue ball when struck, it will not only have reverse spin, but it will have left or right spin. Technically it only has a single axis of rotation, but it has components of both reverse and left right spin, and its easier to think of it that way. This type of spin on the cue ball can cause it to curve. With sufficient amounts of this type of spin it can curve enough to reverse direction. This extreme shot is called the massé shot. A lesser amount of this effect results from the semi-massé shot. An even lesser amount of this results from unintentional applications of this type of cue ball rotation. Hitting the cue ball below center and left or right of center (such as when your bridge hand is resting on the rail,) almost always results in some curve to the balls path. This, of course, often causes the shooter to miss. This is called swerve by some (to differentiate it from an intentional attempt to curve the path of the cue ball.) Swerve is also used as a synonym for curve (see below.)

The semi-massé ("curve" or "swerve") shot

A cue ball can be made to curve in its path of travel. This is usually employed for the purpose of avoiding an interfering ball or balls. In order to achieve a curve, a player's cue stick must be elevated and the cue ball struck with english. A curve to the left is accomplished by hitting the cue ball with an elevated cue and left-hand english. A curve to the right is accomplished by hitting the cue ball with an elevated cue and right-hand english. The higher the elevation of the cue, the more steep the degree of curve. The more speed a cue ball is hit with the farther it will travel in the direction it was hit before beginning to curve.

Such shots are typically referred to as "curve shots" by North Americans and "swerve shots" by the British.

Very steep curves and even reversal of the cue ball path of direction a few moments after being struck can be accomplished by elevating the cue stick to a high degree of elevation. Such large scale curves and reversals of direction are much more difficult and are referred to as massé shots (see below).

The massé shot

Massé refers to imparting a high degree of spin along both the vertical and horizontal axes of the cue ball so that it sharply curves or even reverses direction without having to contact another ball or rail. A massé is performed by hitting the cue ball with a highly elevated cue stick (compare semi-massé). In general, the degree of the curve depends upon the distance from the center of the ball that the contact is made (the further from the center that the tip contacts the cue ball, the sooner the ball will begin to curve). The "delay" between the time that the ball is hit and the time that it starts curving is determined by the elevation of the cue butt (the more elevated it is, the more the ball curves). Massés are quite difficult and are not allowed in some venues, as the table's cloth can be easily damaged by unskilled players.

Other key techniques

Throw

If a ball has sufficient left or right spin on it, when it hits another ball, it can affect the path of that ball after impact. This is due to the spin on the ball throwing the impacted ball off the normal (tangential) line of travel.

Throw refers to an object ball's motion away from the impact line due to relative sideways sliding motion between the cue ball and object ball caused by sidespin or a cut angle.

When a ball with english (sidespin) on it hits an object ball with a degree of fullness, the object ball will be "thrown" in the opposite direction of the side of the cue ball the english was applied. Thus, a cue ball with left hand english on it will "throw" a hit object ball to the right.

Intermeshing gears in motion

This effect is sometimes overarchingly referred to as "the gear system;" so-called because the interaction of the cogwork gears of a clock — each circular gear is interlocked with an abutting circular gear and each spins in the opposite direction of its neighbor in a series. English on the cue ball can cause a very similar effect. If the cue ball with left hand english in the preceding scenario contacts an object ball relatively full and that object ball is frozen to another, the first object ball is thrown to the right and the second to the left, exactly as the name implies. Gears. ...

Throw is also imparted to a ball by collision from a cue ball with no english on it through friction. This is sometimes called "collision-induced throw." The direction of the throw depends entirely on the direction the cue ball hits the object ball from. Unlike throw cause by spin, friction from a collision induced throw "pushes" the cue ball in the same direction as the cue ball was traveling before impact. Thus, a cue ball traveling from the left will cause an impacted object ball to be thrown slightly to the left of the natural angle it would otherwise be sent.

Both varieties of throw are highly influenced by speed. Generally, the less momentum the cue ball possesses at the time of impact, the more throw will affect the object ball's resultant path of travel.

Deflection (squirt)

Deflection can be described as displacement of the cue ball from the aimed direction in the opposite direction of the side english was applied. Like the swerve effect, deflection is an unwanted complicating factor in pool, present whenever english is employed.

The physics of deflection has been studied extensively. Basically, when english is used, the cue ball will always begin its travel in a direction not exactly as aimed; it will "squirt" off of the line parallel with the cue's direction. Deflection increases the faster the cue stick is traveling at impact and the more english has been applied.

Deflection can be decreased by the type of cue used, and at the high levels, players will often select a personal playing cue based on the amount of squirt the cue imparts (the less the better).

Because swerve and deflection (for very different reasons) each cause the cue ball to take a different path than aimed, but each does so in the opposite direction of the other, under the right conditions swerve and deflection can cancel each other out.

The jump shot

A jump shot describes any shot where the cue ball is intentionally driven into the air in a legal manner. It is not permissible in some games (e.g. Snooker) and may be frowned upon or even forbidden in some venues as attempts at it by unskilled players may cause damage to a table's cloth. A legal jump shot requires that the cue ball be hit above center, driving it down into the table, such that the ball will leave the table surface on a rebound. All authoritative rule sources deem it illegal to "scoop" under the cue ball with the tip of the cue to fling it into the air (technically because it is illegal to contact the cue ball with the ferrule of the cue, and because the cue ball is struck twice, both of which are classic fouls).

Unintentional small jumps are ubiquitous to billiards. In most billiards shots, a player's cue is slightly elevated. Whenever a ball is struck with an elevated cue, a jump, no matter how slight, occurs. An oft-used way to illustrate this principle is to lay a coin on the table approximately an inch in front of the cue ball. When shot very softly, the player will audibly hear the coin being struck and see the cue ball's reaction to that collision. When the same shot is performed with any degree of speed no sound or collision is evident, and it is clear that the coin is being jumped.

Speed Control

Speed control is very important skill in all forms of billiards. If you hit the cue ball with the correct spin and direction but the cue ball ends up at the wrong end of the table, the next shot is going to be much harder to make. Learning to hit the cue ball with the correct speed takes practice. And every table has a different "speed", so the billiard player must adjust for this as well.