ANy mathematicians/Physicists in here?

Handsumm

Handsumm

Banned
Ok, well this problem doesn't seem complex, but it is.

I was just thinking...I know that when a cue ball cuts an object ball and center is used (ie. no sidespin) that it induces a sidespin on the object ball. This is why very many beginners find that they missed a cut shot, even though they hit the right spot that they lined up. To combat this, better players usually cut balls with a little English/sidespin. Buddy Hall calls it "helper English."

Now, my question is this..Is there a way to determine how much sidespin (ie. 1/2 tip,one tip, etc.) must be used on a particular angle at a particular speed, to cancel out the effects of contact induced throw.
 
belmicah said:
Ok, well this problem doesn't seem complex, but it is.

I was just thinking...I know that when a cue ball cuts an object ball and center is used (ie. no sidespin) that it induces a sidespin on the object ball. This is why very many beginners find that they missed a cut shot, even though they hit the right spot that they lined up. To combat this, better players usually cut balls with a little English/sidespin. Buddy Hall calls it "helper English."

Now, my question is this..Is there a way to determine how much sidespin (ie. 1/2 tip,one tip, etc.) must be used on a particular angle at a particular speed, to cancel out the effects of contact induced throw.
Click to expand...

Ok, say for instance you have an object ball which is like 2 diamonds x 2 diamonds apart (it's not on the spot though but makeable). Your cueball is like at a 45 degree angle apart of the OB on the left side of the contact point of the target. When you hit the cueball center to make that OB, you have inserted (automatically) right english on the OB (due to friction). Usually, it's not a bad thing to adjust a tad left of your aiming line... OR you can compensate it with one tip of left English and a medium stroke. But, if you want to put more throw into the shot, then put one tip of right and go between a medium to medium-soft shot. Throw is what usually gets so many inexperienced players into frustration. When one puts English on a shot, it will eventually throw... but the speed of the shot will determine whether it will throw alot (a soft stroke) or throw minimally (a harder stroke).
 
This is a question for Bob Jewett, of course. :-)
But in general half a tip should be plenty.
You could go into more detail and read J. Koehler's book "The science of pocket billiards" or the two articles by Ron Shepard. I believe the titles are: "Amateur physics for the amateur pool player" and "Everything You Always Wanted to Know About Cue Ball Squirt, But Were Afraid to Ask" which you can find on the web.
 
Sometimes, you may just want to cut it a little more too, ie shots where you dont want sidespin on the ball for position play. Its no different than learning aim point contact point on any other shot. Its just that sometimes the contact point is NOT on the same line as the center of the object ball and the center of the pocket.
Chuck
 
belmicah said:
...Now, my question is this..Is there a way to determine how much sidespin (ie. 1/2 tip,one tip, etc.) must be used on a particular angle at a particular speed, to cancel out the effects of contact induced throw.
Click to expand...
Yes. Picture the contact point on the object ball (the point opposite the pocket). It will be a certain distance from the center of the object ball as you look at it from your shooter's perspective (over the cueball). Make tip contact on the cueball at 2/5'ths or 0.4 of this distance from the center of the cueball (as you look at the cueball from your shooter's perspective down the aim line). Of course, we're talking outside english here.

The above applies when the cueball is close enough to the object ball and/or you're shooting hard enough so that the cueball will hardly slow any on the way to it. If it will slow down appreciably, you have to strike closer to center. There is a variation of the above method if the cueball will reach natural roll before impact.

Another way, but this is more theoretical, is to hit the cueball a little faster than lag speed with either full follow or full draw. The compression of the balls should, in theory, cancel what little throw you do get. But just rolling the cueball or having a lot of backspin on it at any speed reduces throw to relatively small values.

I think many would question as to whether it's a good idea to use english or draw/follow for anything other than position. But particularly on those long ones, you have to do what you have to do, I guess.

Jim
 
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belmicah said:
Ok, well this problem doesn't seem complex, but it is.

I was just thinking...I know that when a cue ball cuts an object ball and center is used (ie. no sidespin) that it induces a sidespin on the object ball. This is why very many beginners find that they missed a cut shot, even though they hit the right spot that they lined up. To combat this, better players usually cut balls with a little English/sidespin. Buddy Hall calls it "helper English."

Now, my question is this..Is there a way to determine how much sidespin (ie. 1/2 tip,one tip, etc.) must be used on a particular angle at a particular speed, to cancel out the effects of contact induced throw.
Click to expand...

So there is a little more detail in this than you are addressing here. But I believe I might be able to shed some light on this.

First off, when a cue ball strikes an object ball, there are many things that happen that can affect the outcome of the object ball's path. As you mentioned, there is natural spin that is applied to the object ball. This happens because of friction. Even though pool balls are generally very polished, there will still be friction between the two balls, thus causing the stationary object ball to start spinning in the direction of the cue ball's tangent line (or path after striking the object ball). There are many factors that can lead to varying amounts of friction between the two balls such as moisture and how clean the balls are. Moisture and dirty balls will create a higher coefficient of friction and therefore induce more spin on the object ball. So, in essence, it is possible to hit a 50 degree cut shot with the same angle and have very different results depending on the conditions.

Second, when a cue ball strikes an object ball, there is also a natural object ball "skid" that occurs, regardless of speed, before it actually starts rolling in it's final direction. This is basic physics, and it has to do with transer of motion. There is a law called "The Conservation of Energy" in physics that refers to the fact that energy cannot be created or destroyed, it simply changes form (i.e. heat, light, movement, etc...). So upon a collision of a cue ball and object ball, a cue ball will transfer some, or all, depending on angle, of it's energy to the object ball. Now since pool balls are very slick (very low coefficient of friction) and table cloth's are generally fine in texture, the object ball will slide or skid "proportionate" to the energy transferred to it from the cue ball, before they start rolling. In other words, if you hit the cue ball very hard, there will be a large skid by the object ball, and vice versa. Also, the path at which the cue ball strikes the object ball affects the direction of "throw" on the object ball. The throw on an object ball is also directly proportionate to the velocity of the cue ball as well as it's path.

Taking into account spin, skidding, and throw, along with many others I've neglected to mention for the sake of length, there can be many reasons an easy cut shot can be missed, even though the exact point of contact (ghost ball point of contact) is struck. But to have an exact, detailed formula for how much english to apply on cut shots is difficult to summarize because there are so many varying factors.

- How far is the cue ball from the object ball? If the distance is further, then less english is needed as the cue ball will have more time for the spin applied to it to take affect. If the distance is shorter, then the converse is true, and more english can be applied for the exact same effect.

- How hard must the shot be hit (to get necessary shape)? The harder a shot must be hit, the more skid and throw an object ball will experience. Therefore, if you know a shot must be hit hard, then you know you must hit it with a little more angle than usually required to account for throw and spin will be less of a factor because of the amount of skidding. If the shot must be hit more softly, then you know you can use a "truer" angle or even less if using what you called "helper english". The slower speed will allow for greater transfer of spin and therefore the object ball will take more english. Throw won't be as much of a concern, but cue ball english will be more pronounced because of it and thus cause a greater degree of error for the object ball path after collision.

The sidespin you apply must account for all of these factors and will not be consistent for the same shot with the same speed every time. Experimentation will be your best way of determining and other issues like cue angle (from 0 degrees parallel with the table) will also affect the path of the cue ball with english. And the "helper english" you speak of is generally to help avoid the effects of throw.

Hope this helps.
 
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belmicah said:
Now, my question is this..Is there a way to determine how much sidespin (ie. 1/2 tip,one tip, etc.) must be used on a particular angle at a particular speed, to cancel out the effects of contact induced throw.
Click to expand...

From The Science of Pocket Billiards by Jack H. Koehler

"One must be able to make accurate estimates of how much aim adjustment is required when a specific amount of side english is used. One way to improve the accuracy of these estimates is to practice on paper. Draw a table with several object balls and a cue ball. Make an estimate of the correction required for each shot using left and right english. After working out a few hundred of these shots on paper, your estimated correction should be fairly accurate."

In other words, do repeated shot experiments to see what you require to make a shot for a particular speed, distance and angle.:D

And you were looking for an easy answer.:D
 
BigCat said:
...The throw on an object ball is also directly proportionate to the velocity of the cue ball as well as it's path.

...The harder a shot must be hit, the more skid and throw an object ball will experience. ...
Click to expand...
You made many good points but I have to nitpick a little with these. Generally speaking, throw diminishes with greater cueball speed, and an object ball does not go down different paths according to how long it skids. There are some very small effects, but they are so small that they really can't be said to affect the shot in any practical sense, unless maybe you contact the object ball somewhat above its equator. But for what it's worth, I think I agree with everthing else you said. Nice post.

Jim
 
belmicah said:
Ok, well this problem doesn't seem complex, but it is.

I was just thinking...I know that when a cue ball cuts an object ball and center is used (ie. no sidespin) that it induces a sidespin on the object ball. This is why very many beginners find that they missed a cut shot, even though they hit the right spot that they lined up. To combat this, better players usually cut balls with a little English/sidespin. Buddy Hall calls it "helper English."

Now, my question is this..Is there a way to determine how much sidespin (ie. 1/2 tip,one tip, etc.) must be used on a particular angle at a particular speed, to cancel out the effects of contact induced throw.
Click to expand...

You would have to experiment, I don't think there is any easy answer.

However I think it is better to be able to cut balls in without applying any side to the ball. If have to use inside english to pot a specific shot, what do you do if need to use outside to get on the next ball?
 
If you notice good players almost always hit all balls with a good stroke instead of slow- rolling them. They either stun, draw, or follow a lot to move the ball into position on the shot. That’s why you see a good player get upset with him/herself when they get a little out of line for the next shot. They know that now they have to use MORE english on the next shot to make the ball and get back in line. They all prefer to only use a small amount of natural or running english to get to the next ball. They know the more spin they have to put on the ball harder the shot becomes. I'm sorry I don't know why I wrote this. We all know this. Johnnyt
 
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