tangent line
- Thread starter berlowmj2
- Start date
You really need to get Joe Villapando's DVD on cue ball control! It will answer all your questions. In the meantime experiment hitting the cue ball with center ball 1/8th" above center. 1/4" above center. Then center ball 1/8" below center and 1/4" below center. Try these shots almost straight on into the side pocket and watch the cue ball reaction. This DVD is will definitely show you how to move the cue ball around the table and I guarantee it will improve your game.
Correct me if I'm wrong, instructors.
You can't change the tangent line .
You can only change the cueball path after collision.
You can't change the tangent line .
You can only change the cueball path after collision.
Joey is correct. You cannot "influence" or change the tangent line. Only top and bottom spin affect the CB path after contact. Tangent line refers to the path of CB after contact with the OB, when the CB skids or slides into contact...not rolling. Pure sidespin has no effect on tangent line (unless there is top or bottom added). To see a very clear explaination of tangent line physics, see our dvd, Play Better Pool, Vol. 1, Mastering the Basics.
Scott Lee
www.poolknowledge.com
Scott Lee
www.poolknowledge.com
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How do you define 'tangent line'?
Never mind...I'll give you the answer. The tangent line of a sphere is the line that touches just one point. The radius of the sphere to the point of tangency is always perpendicular to the tangent line. Therefore you can never "influence" a tangent line. You can change it only by changing the point of contact.
What I think you are asking is how can you manipulate the cue ball to veer off of the tangent line at various points. As far as I know, the answers are with top spin and back spin. Some say with side spin, although I tend to agree that it's possible, I'm not totally clear on the physics of that. I'm sure Bob Jewett can help with that.
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Scott I'm reading your post head going up and down till you say "when the CB skids or slides into contact...not rolling" Are you saying the tangent line is simply the line formed by the contact points and this can be changed simply by using high or low tip placement???
Your first say "You cannot "influence" or change the tangent line." I kind of agree with this as well as the above quote but its my feeling that the CB MUST take the tangent line for some distance and that distance is determined by the speed of the CB @ contact and that the influence of high or low (altering the tangent) comes at some time after the tangent is taken.
IMO this (speed) is the essence of CB control playing Center Ball/Vertical Axis.
Back to you.
What a great question.
First off there are only three things that we can control in pool. That would be the Angle, Speed & Spin from the cue stick to the cue ball.
The Tangent Line starts at cue ball release, not cue ball contact.
Then it is always 90 degrees.
How far the cue ball travels down the Tangent Line is influenced by Speed and/or Spin.
Side Spin does nothing to affect the Tangent Line until the cue ball touches a rail.
A Stop Shot (no top or bottom spin) will stay on the TL for quite a long time.
To give a direct answer: We can not affect the TL, only how the Cue ball travels down it.
randyg
First off there are only three things that we can control in pool. That would be the Angle, Speed & Spin from the cue stick to the cue ball.
The Tangent Line starts at cue ball release, not cue ball contact.
Then it is always 90 degrees.
How far the cue ball travels down the Tangent Line is influenced by Speed and/or Spin.
Side Spin does nothing to affect the Tangent Line until the cue ball touches a rail.
A Stop Shot (no top or bottom spin) will stay on the TL for quite a long time.
To give a direct answer: We can not affect the TL, only how the Cue ball travels down it.
randyg
Thanks for correcting me Scott i belleve i meant very minimally with side spin if hit at a cut angle and a lot of spin very slowly and then not much mostly a lot with follow or draw. The same way you can cut a shot to thin and shallowit out with english to a very small amount and hit one to full and still make it with throw when another ball is blocking a shot just enough to not be able to hit your target point exactly. Sorry i didnt mean to mislead anyone. This may not be possible with super clean balls but with balls that have some use on them maybe i know i do it occasionaly.
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Randy is correct i hit a stop shot on the 9 on my table last week and the cue ball is still on that tangent line still waiting to see if it deviates.
Simple physics says that the cue ball will leave the collision with the object ball along the tangent to the contact point. This is a fairly simple result that might be taught in a high school physics course. It is mostly the result of conservation of energy and conservation of momentum. At least four assumptions go into the result: there is no sideways force at the contact point, no energy is lost in the collision, the balls are the same weight and size, and both balls are at the same height at the time of the collision.
On closer examination, at least one of those assumptions is wrong on every shot. That means that the cue ball almost never leaves the collision exactly perpendicular to the line the object ball takes out of the collision. How inexactly? That depends.
Due to sideways friction during the collision, several things happen. The object ball is pulled left or right of the line through the centers of the balls at the time of the collision (throw). That can be up to 6 degrees. This also causes the object ball to spin and the cue ball to slow down or speed up (a little) compared to the speed it would have without the throw. The direction of the cue ball is not changed by this effect but its spin is changed in the same amount that the object ball gains spin.
Energy is in fact lost in the collision. This will cause the cue ball to go forward of the expected line so the angle between the two ball paths will be less than 90 degrees. The angle change depends on the fullness of the hit and the "elasticity" of the balls. This effect is more noticeable with ivory balls because ivory is much less elastic than phenolic. You probably won't notice this effect except on some special shots.
The cue ball is often not the same size or weight as the object balls, due to wear. A heavy cue ball will tend to smash through the collision and a light cue ball will tend to bounce back. The change in the angle again depends on the cut angle.
Finally, if the cue ball is off the table at the time of the collision, which often happens when you are jacked up and shooting at a close object ball firmly, the path of the cue ball will appear to be ahead of the normal tangent line. In fact, the cue ball may be traveling along the real tangent line, but that tangent is to a point that is no longer on the equator of the object ball. An extreme case of this is when you shoot a jacked-up draw shot and the cue ball jumps forward before it draws back. In that case, the apparent change in cue ball path is 90 degrees.
On closer examination, at least one of those assumptions is wrong on every shot. That means that the cue ball almost never leaves the collision exactly perpendicular to the line the object ball takes out of the collision. How inexactly? That depends.
Due to sideways friction during the collision, several things happen. The object ball is pulled left or right of the line through the centers of the balls at the time of the collision (throw). That can be up to 6 degrees. This also causes the object ball to spin and the cue ball to slow down or speed up (a little) compared to the speed it would have without the throw. The direction of the cue ball is not changed by this effect but its spin is changed in the same amount that the object ball gains spin.
Energy is in fact lost in the collision. This will cause the cue ball to go forward of the expected line so the angle between the two ball paths will be less than 90 degrees. The angle change depends on the fullness of the hit and the "elasticity" of the balls. This effect is more noticeable with ivory balls because ivory is much less elastic than phenolic. You probably won't notice this effect except on some special shots.
The cue ball is often not the same size or weight as the object balls, due to wear. A heavy cue ball will tend to smash through the collision and a light cue ball will tend to bounce back. The change in the angle again depends on the cut angle.
Finally, if the cue ball is off the table at the time of the collision, which often happens when you are jacked up and shooting at a close object ball firmly, the path of the cue ball will appear to be ahead of the normal tangent line. In fact, the cue ball may be traveling along the real tangent line, but that tangent is to a point that is no longer on the equator of the object ball. An extreme case of this is when you shoot a jacked-up draw shot and the cue ball jumps forward before it draws back. In that case, the apparent change in cue ball path is 90 degrees.
Of course Randy is correct and I think Scott is too but for clairification for myself and maybe others I'm digging down.
Randy states: "The Tangent Line starts at cue ball release, not cue ball contact. Then it is always 90 degrees."
Randy is going back to the source, I believe, stating the tangent is derived when the CB leaves the tip which in turn defines the Contact Point rather than our intended contact point or desired/planned tangent.
I always say the TL is Defined by the Contact Point. I'm not quite sure if we're in agreement or not.
My problem is achieving and maintaining my desired TL over great distances, but that's another topic although of great interest to me and why I'm digging here a little. Not complaining or arguing.
Randy sorry if I put the wrong words in your mouth here.
Randy states: "The Tangent Line starts at cue ball release, not cue ball contact. Then it is always 90 degrees."
Randy is going back to the source, I believe, stating the tangent is derived when the CB leaves the tip which in turn defines the Contact Point rather than our intended contact point or desired/planned tangent.
I always say the TL is Defined by the Contact Point. I'm not quite sure if we're in agreement or not.
My problem is achieving and maintaining my desired TL over great distances, but that's another topic although of great interest to me and why I'm digging here a little. Not complaining or arguing.
Randy sorry if I put the wrong words in your mouth here.
What is "cue ball release" and how does it differ from "cue ball contact"?
Changing the Trangent Line
My 2 cents on the question - or atleast how I got what he was asking.
I think you can change the tangent line in a couple ways. Say a slight cut into the side pocket. If you shoot the Object Ball dead center in the pocket with a stop shot the cue ball comes off at 90 degrees (hence the tangent line).
1st way to change the tangent line: Cheat the pocket and depending on how far the Object Ball is from the pocket you can vary the original tangent line by several degrees (still using a stop shot).
2nd way you can cheat the pocket even more with throw. Doing this you can add a few more degrees of variance from the original shot.
Does that all make sense? Does that seem to answer his original question?
My 2 cents on the question - or atleast how I got what he was asking.
I think you can change the tangent line in a couple ways. Say a slight cut into the side pocket. If you shoot the Object Ball dead center in the pocket with a stop shot the cue ball comes off at 90 degrees (hence the tangent line).
1st way to change the tangent line: Cheat the pocket and depending on how far the Object Ball is from the pocket you can vary the original tangent line by several degrees (still using a stop shot).
2nd way you can cheat the pocket even more with throw. Doing this you can add a few more degrees of variance from the original shot.
Does that all make sense? Does that seem to answer his original question?
This one is probably the most useful one to note. This might change the cue ball's direction by as much as +-6 degrees even if the object ball goes to the center of the pocket. The only other method the player has control over that can have a larger effect is a semi-jump shot as described above.