Which shot allows for the greater margin of error?

What shot allows for the greater margin of error?

  • the 8ball has the greater margin of error

    Votes: 36 62.1%

  • the 9ball has the greater margin of error

    Votes: 10 17.2%

  • both have the same margin of error

    Votes: 12 20.7%
  • Total voters
    58
jsp

jsp

AzB Silver Member
Silver Member

CueTable Help



Both the 8ball and 9ball are straight-in shots to the corner pocket (Don't think of it as a combination shot, but two independent shots). The 8ball is a ball's width away from the pocket opening, and the 9ball is a ball's width away from the CB.

What shot do you think allows for the greatest margin of error (in alignment)? Assume that you can't rattle either ball in the pocket...i.e. if the OB hits the sides of the pocket before half of it is already through the pocket opening, the shot won't go in.

Just curious what people think.
 
the 8 is marginally more difficult. the distance between the balls invites more things to go wrong, especially with english.
 
I believe they are equally as difficult. With the 8-ball it is true you have a lot of green and things can go wrong. However, with the 9-ball you must elevate the back end of the cue to execute the shot, therefore if you do not hit the cueball dead-center, things could also go wrong. In both cases either the cueball or the 9-ball must travel the entire length of the green...and, things could go wrong. Personally, I would prefer to shoot the nine because I am blind in one eye and I can't see out of the other!
 
Margin of error

Basically, the 9 is a mechanic problem, and the 8 is a mechanic and eyesight problem. (Think reading a newspaper as opposed to reading
text on a TV 8 feet away).
 
I think the 8 is easier. If the 9 is a touch off dead straight, judgement comes into play and can be deceptive. With the 8, you can hit it a couple of mm either side, so as long as your long shot allignment is pretty good, it shouldn't be a problem.

Some folks have different visual allignment capabilities though.
 
there's some things that can affect the 9ball shot that wouldn't affect the 8.

throw, for instance. the 9 is close enough that if you're off on your hit on the cb, a slight amount of unexpected english can throw the 9 off.

i also think visually, it's easier to see the line to the pocket on the 8 than it is on the 9.

and the 8 is simply closer to the pocket, making for a wider angle to miss.
 
Definitely the 8 has wider latitude. If you were to go line up the 8 to the most extreme part of the 8ball that it could still be pocketed on either side of the pocket, you would have a target area of up to 3" to hit and still be able to make it.

The farther away you are, as with the 9ball, that area diminishes to a very minute contact point.
 
A rule of thumb in pool is that the farther an object ball is away from it's destined pocket, the less margin for error you have. Any problem in your alignment on a straight in shot on the 9 like you showed, becomes magnified as the 9 keeps moving forward. Your alignment could be off by a centimeter and it could turn into you missing the ball by half a foot, etc.

If a ball is sitting in the jaws of a pocket, the entire side of the ball that you are looking at is a huge contact point (duh). You can hit it anywhere and it will still go in the hole. If a ball is a few inches away from a pocket, the same thing applies, but the margin for error to still pocket the ball is smaller than if the ball is sitting in the jaws. Move the ball even further from the pocket, the margin for error becomes smaller and smaller.

You can't argue that if the cueball is very far from an object ball in the jaws of the pocket, it should also be difficult, because remember the margin for error is the contact point that the cueball must strike to pocket the ball. With a ball in the jaws, and the cueball across the table on the rail or in the jaws of another pocket, that shot is about as difficult as hitting the end rail. You can hit the end rail, cant you? :D
 
All interesting answers. However, I was looking at it more as a geometry problem than a practical problem. Just assume perfect conditions...i.e. perfect cloth, no friction/throw, no swerve,etc.

Ideally, you want the CB to travel straight down the path designated by the red arrow to pocket either the 8ball or 9ball (the red arrow is a line that goes through the exact centers of the CB, 8ball, 9ball, and pocket). However, let's say you're misaligned (or your stroked is off) and you actually hit the CB at a trajectory angle alpha away from the ideal CB path (alpha is your error angle).

Which ball allows you to have the biggest alpha (error angle) while still pocketing the ball (the OB would go through the extreme end of the pocket)?

I worked out the geometry (if my 9th grade math is correct), so there is an answer to this problem.
 
jsp said:
What shot do you think allows for the greatest margin of error (in alignment)? Assume that you can't rattle either ball in the pocket...i.e. if the OB hits the sides of the pocket before half of it is already through the pocket opening, the shot won't go in.

Just curious what people think.
Click to expand...

if you missed the 8 by plus or minus 13 degrees, the ball will still go. (the red line in the following digrams shows a 26 degrees pivot angle)

if you missed the 9 by anything more than 0.5 degress to either side, the ball will not go. (the yellow line in the following digrams shows a 1 degree pivot angle)



I found this by using the angle calculation function of cuetable. If you draw a line with turns, it will show you the total line distance and last pivot angle counts at each mouse click. Please see below :)

Cuetable Link: Angle Analysis

cheers
wei
 
Last edited:
I think what JSP is trying to say is which shot has a greater margin for error in cueball angle from center. Not the object ball angle.
 
jsp said:
All interesting answers. However, I was looking at it more as a geometry problem than a practical problem. Just assume perfect conditions...i.e. perfect cloth, no friction/throw, no swerve,etc...
Click to expand...
I think the margin of error is slightly greater for the 9-ball, but for all practical purposes, they're the same. Nevertheless, I would probably feel more confident shooting the 8-ball (go figure).

Jim
 
wertqea

i dont know if this is an old theory or not... nor do i know where it came from but i know when i look at making any ball and decide the margin or error i draw a mental triangle from the contact point of the OB to the inside of each side of the pocket.

that being said the triangular angle one the 8 ball would be much wider and allow for more error, ie an actually wider angle for the cb to contact the ob and still make it.


i think the mechanical problems that would arise of the nine would also arise just the same on the eight.


just my opinion... hope it helps
 
If cue ball is alpha off the line to the pocket, the 9 ball will be alpha off in the opposite direction(alpha2). The 9 will cross, or start on, the line to the pocket and continue on the alpha2 course. Because the cue ball, if shooting the 8, would vary from the line at a farther distance from the pocket than the 9, it would be farther off the line to the pocket. Clear as mud, right?
 
jsp said:
All interesting answers. However, I was looking at it more as a geometry problem than a practical problem. Just assume perfect conditions...i.e. perfect cloth, no friction/throw, no swerve,etc.

Ideally, you want the CB to travel straight down the path designated by the red arrow to pocket either the 8ball or 9ball (the red arrow is a line that goes through the exact centers of the CB, 8ball, 9ball, and pocket). However, let's say you're misaligned (or your stroked is off) and you actually hit the CB at a trajectory angle alpha away from the ideal CB path (alpha is your error angle).

Which ball allows you to have the biggest alpha (error angle) while still pocketing the ball (the OB would go through the extreme end of the pocket)?

I worked out the geometry (if my 9th grade math is correct), so there is an answer to this problem.
Click to expand...


well,,,that sound DOES sound like a geometry problem to me. the 9 has a smaller room for error, but you lay closer to the OB so you can be more accurate with the hit. the 8 is farther away and you won't be as accurate, but the 8 allows for a wider latitude of error.

i wouldn't be surprised if they ended up the same.
 
I would think the 9 ball shot would require more accuracy, however as a practical matter, if I step away from the table about 6 feet and look at the shot, then get down low to shoot this shot and look at the alignment of the tops of the balls, then I can shoot it with more accuracy. So in practice, the 9 would be an easier shot for *me*.

If just pocketing the 8, I feel this would require less accuracy. But as a practical matter, I would have more trouble with *this* 8 ball shot because it is straight in. (If there was a slight cut, then piece of cake.) And this is if I was trying to keep the cue ball from following the 8 into the pocket.

If I shot the cue ball very slowly with just enough speed to pocket the 8 ball, then I GUARANTEE the table would not be level and the cue ball would curve before hitting the 8 -or- there would be some particle or dirt on the cloth and it would make the cue ball change course! Or if I attempted a stun shot and had to shoot down on the cue ball because it is so close to the pocket, then I would be less likely to pocket the 8. So in practice, the 8 would be a more difficult shot for *me* (If trying to avoid scratching).
 
bruin70 said:
well,,,that sound DOES sound like a geometry problem to me. the 9 has a smaller room for error, but you lay closer to the OB so you can be more accurate with the hit. the 8 is farther away and you won't be as accurate, but the 8 allows for a wider latitude of error.

i wouldn't be surprised if they ended up the same.
Click to expand...
That's what I thought.

But actually the 9ball (the ball closer to the CB) has signifcantly more margin of error than than the 8ball (the ball closer to the pocket). Here are the numbers I used...

CB distance to pocket opening = 10 feet (120'')
pocket size = 4.5''
8ball distance to front edge of pocket opening = 2.25'' (to the front edge of the 9ball)
9ball distance to CB = 2.25" (ball edge to ball edge)

Results...
8ball margin of error = +/- 0.356 degrees
9ball margin of error = +/- 0.558 degrees

So the 9ball has about 57% MORE margin of error than the 8ball. Those numbers don't sound very big. However, compare it to the worst case margin of error with the OB (as you would expect) being right at the midpoint between the pocket and CB. The margin of error in this case is a miniscule +/- 0.042 degrees.

I always thought that margin of error would be pretty much symmetric around the midpoint between the CB and pocket. After graphing the solution, it more or less does look symmetric until the OB gets a couple of ball's widths distance away from the CB and pocket. At this closer proximity, the margin of error on the CB side goes up much faster than the pocket side.

If you're not convinced, just think of the extreme case of the 8ball hanging right on the edge of the pocket compared to the 9ball being virtually frozen on the CB. For the 9ball, you can pretty much aim in any foward direction (again, neglect throw and friction effects) and the 9ball should head towards the pocket. Your margin of error is huge...pretty much the full 180 degrees. However, to pocket the 8ball, you still need to have the CB contact the 8ball, so your margin of error is still very limited.

So going back to the original example, you should be able to pocket the 9ball about 50% more times than the 8ball...in theory. It's funny how the practical world doesn't exactly agree with the theory.

Neat, huh? If anyone is interested, I'll post my derivations and calculations...NOT! :p
 
Last edited:
jsp said:
That's what I thought.

But actually the 9ball (the ball closer to the CB) has signifcantly more margin of error than than the 8ball (the ball closer to the pocket). Here are the numbers I used...

CB distance to pocket opening = 10 feet (120'')
pocket size = 4.5''
9ball distance to front edge of pocket opening = 2.25'' (to the front edge of the 9ball)
8ball distance to CB = 2.25" (ball edge to ball edge)

Results...
8ball margin of error = +/- 0.356 degrees
9ball margin of error = +/- 0.558 degrees

So the 9ball has about 57% MORE margin of error than the 8ball. Those numbers don't sound very big. However, compare it to the worst case margin of error with the OB (as you would expect) being right at the midpoint between the pocket and CB. The margin of error in this case is a miniscule +/- 0.042 degrees.

I always thought that margin of error would be pretty much symmetric around the midpoint between the CB and pocket. After graphing the solution, it more or less does look symmetric until the OB gets a couple of ball's widths distance away from the CB and pocket. At this closer proximity, the margin of error on the CB side goes up much faster than the pocket side.

If you're not convinced, just think of the extreme case of the 8ball hanging right on the edge of the pocket compared to the 9ball being virtually frozen on the CB. For the 9ball, you can pretty much aim in any foward direction (again, neglect throw and friction effects) and the 9ball should head towards the pocket. Your margin of error is huge...pretty much the full 180 degrees. However, to pocket the 8ball, you still need to have the CB contact the 8ball, so your margin of error is still very limited.

So going back to the original example, you should be able to pocket the 9ball about 50% more times than the 8ball...in theory. It's funny how the practical world doesn't exactly agree with the theory.

Neat, huh? If anyone is interested, I'll post my derivations and calculations...NOT! :p
Click to expand...

JSP, I commend you. You always show a willingness to do the calculations that I think I could probably do, but it would take way more time and mental effort than I'm willing to invest. Are you by any chance a math teacher? I ask because I know very few people willing to derive geometry equations for fun :p

-Andrew
 
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