How do you know which way the object ball will throw for different types of shots?

For the basics, see the throw section in the online Pool Tutorial.

Throw direction depends on the direction of the relative motion of the surface of the cue ball in contact with the object ball. This direction is affected by both cut angle and spin. “Throw – Part VI: inside/outside english” (BD, January, 2007) and “Throw – Part VII: CIT/SIT combo” (BD, February, 2007) illustrate the different possibilities quite well. Here’s a good video demonstration and explanation of both cut-induced throw (CIT) and spin-induced throw (SIT):

See also:

A complete summary of all squirt, swerve, and throw effects can be found here.

Is the contact point on the OB the same for shots with draw, stun, follow?


See the effects of draw and follow on throw resource page.

The contact point is at the theoretical point along the line to the pocket (along the “line of centers”) only for a gearing outside english shot. For visual proof, see:

The visual evidence is very clear, and you can also easily reproduce this stuff at a pool table yourself.

Do CIT and SIT add or subtract as independent factors?

Object ball throw depends on cut angle, shot speed, type and amount of english, and the amount of vertical plane spin (draw, follow, stun). The following series of instructional articles elaborate on all of these factors:

Collision-induced throw (CIT) and spin-induced throw (SIT) are just different names for throw, depending upon the primary cause of the throw, but the effects don’t really combine as separate factors.

Outside english (OE) can diminish, eliminate, or even reverse the direction of throw. But at larger cut angles, a small amount of OE can actually increase the amount of throw (e.g., see Diagram 1 in “Throw – Part VII: CIT/SIT combo” (BD, February, 2007)). Again, the reason has to do with the relative surface speed between the balls. Sliding friction (and therefore throw) is greater at slower relative surface speeds. With larger cut angles, inside english (IE) increases the relative surface speed between the balls and reduces the amount of friction and the amount of throw. For a large cut angle, a small amount of OE can reduce (but not reverse) the surface speed some resulting in more friction and more throw.

With “gearing outside english” (gOE) there is no sideways force whatsoever. That’s why there is no throw. The OB heads exactly in the impact-line direction (i.e., in the ghost-ball line-of-centers direction). There can be throw only when there is a sliding force between the CB and OB. With gOE there is no sliding between the balls during contact (see “Throw – Part VI: inside/outside english” – BD, January, 2007). With less-than-gearing OE, throw is in one direction (the CIT direction); and with more-than-gearing OE, throw is in the other direction (the SIT direction). There either is throw or there is not, and it can be in one direction or the other. GOE completely eliminates throw and cling. It’s just tough judging the exact “gearing” amount of OE you need for each cut angle.

Do balls of different sizes (e.g., snooker vs. carom vs. pool) throw the same amount?

See throw ball size effects.

Does the type of cloth affect throw?

No. The cloth has nothing to do with throw. The throwing force pushes the ball in the thrown direction during impact, before the ball has any time to interact with the cloth.

The OB starts off in the same direction regardless of the properties of the cloth. Only once the OB starts moving across the cloth (after CB impact) does the cloth have any effect. The cloth affects how the OB speed and top/bottom spin change during motion, but it does not affect the straight-line direction of OB motion (assuming there is no massé spin on the OB). The OB direction is a direct result of the forces (impact and throw) acting during the incredibly-brief ball contact time. The amount the OB moves during CB impact is negligible. The OB acquires its speed and direction immediately (for all practical purposes).

Cloth condition has many effects (see cloth effects), but throw direction is not one of them. Although, there are some possible indirect throw effects related to cloth condition. With a faster cloth, less speed will be used on most shots, and throw is larger with less speed (see throw speed effects). Also, slow/sticky cloth might wear chalk marks off the CB more which could result is less frequent cling/skid/kick.

Is it possible to use throw to have the CB and OB move sideways in the same direction with a straight shot?

Yes. See:

NV B.21 – Straight shot squirt, swerve, and throw

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