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trhxke
USA
142 Posts |
 Posted - 12/10/2007 : 1:11:00 PM
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Last week we had players on both teams execute a safety shot where they placed the cue on the table surface, slide the tip upto and under the edge of the cue ball then lifted the cue causing the tip to push the cue ball forward into the object ball (the object ball was very close to the cue ball).
I have seen this done before and have never questioned it as being OK under the rules ....but....
Just this morning I read on the BCA Forum that this very shot would be now be considered a foul under the new rules.
Quoting Bob Jewett's post on another board:
"According to the just-adopted World Standardized Rules, you have to shoot with a forward motion of the cue stick that strikes the cue ball. Setting the balls in play in motion any other way is not just a foul but is unsportsmanlike conduct.
Bob Jewett
http://www.sfbilliards.com "
Has the APA considered this shot specifically and is it in fact even legal now?
Tom Hardinger
www.BigRigToys.com
Your Internet Source for pool cues, cases, table accessories, darts and various collectibles.
www.myspace.com/bigrigtom
http://hardingersystems.com/bat-forum/
http://bigrigtom.blogspot.com/ |
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Kerry Randolph
USA
172 Posts |
Posted - 12/10/2007 : 3:12:39 PM
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I had to read your post twice to make sure I was understanding what happened. I have never seen anyone do this. To have it happen twice in a night is amazing. Just off the top of my head as long as there was no double hit and legal contact with an object ball and a rail was made, I would think it would be a legal hit. Strange but legal.
It is better to keep your mouth shut and appear stupid than to open it and remove all doubt |
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poolguy
USA
54 Posts |
Posted - 12/11/2007 : 01:41:18 AM
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This is one of those things that folks try to get away with by taking a strange stroke. I, for one, don't think it should be legal in any rules system. I've read the APA rules and I don't think this is covered at all.
This boils down to a legal stroke. The referenced BCA rules have defined a legal stroke as a forward motion, which I think is appropriate. I'll be curious to see what the official APA ruling on this is. (Note that the players who did this were probably very high skill level players, as they knew what a double hit was and either figured out a way to avoid it or someone told them about this "method".)
John
It only hurts if you miss. |
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Phil
USA
829 Posts |
Posted - 12/11/2007 : 09:22:39 AM
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Define "forward". If I shoot down on the back of the cue ball and angle my cue away from the object ball, am I shooting forward?
The shot Tom mentions is legal in the APA. However, it is NOT guaranteed to produce a good hit. It is still possible to double-hit the cue ball even with this "stroke". If you think about the physics of the shot, what happens is that the tip of the cue traces an arc as it is lifted. The radius of the arc is the length of the cue (or the distance from the tip to the outer edge of the table, if the butt end of the cue is on top of the rail). Since the cue ball is a sphere, it consists of an infinite number of smaller arcs, one of which lies in the same plane as the arc formed by the tip of the cue. In order for the cue ball to move at all, the two arcs must intersect (tangent isn't good enough, that will produce no movement of the cue ball). And as anyone who understands geometry knows, two coplanar circles that intersect must do so in exactly two points. It takes a finite amount of time for the tip to travel from the first point of intersection to the second, during which time it is passing through the space previously occupied by the cue ball. It is possible for the cue ball to return to that space before the tip has passed through the second point of intersection, in which case the result is a double hit.
The physics of this shot are actually the same as the physics of shooting down on the cue ball to avoid a double hit. When shooting down, your tip also traces an arc. If your stroke is straight, the radius of the arc is infinite. Nevertheless, there is still a finite amount of time during which the cue occupies the space where the cue ball was. The difference is that in the first case, the cue leaves the space without changing direction, so it spends less time within that space and the likelihood of a double hit is reduced. Not eliminated, reduced.
Why such a technical explanation? Because the first post mentions Bob Jewett. Bob is a physicist by trade and would appreciate the details of the physics involved, and you should too.  Bob and I have actually had numerous electronic conversations in the past about such things, including the physics of a "swerve stroke".
Now, why does APA consider this shot legal? Because it falls into the category of "too technical to legislate". What if I did essentially the same thing, only I kept my bridge hand under the cue and held the back end with the other hand? I could produce the same cue motion from this starting position. Would you be able to tell if the motion was "forward"? What if I was holding the cue with the tip above the edge of the cue ball, and accidentally let the tip drop? This is the same tip motion, only in the opposite direction. If it produced a good hit, would it be a foul? What if it wasn't accidental? Would you be able to tell? These are legitimate questions that are difficult to answer if you try to legislate the stroke. The APA feels that the best thing for our players is to avoid all of these issues with a simpler set of rules. If you contact the cue ball with your cue, it makes contact with a legal object ball, and something hits a rail or goes into a pocket, it's good - no need to concern yourself with how the initial contact was made.
By the way, this isn't the only clever way to avoid a double hit. I can do it with a HARD, FORWARD stroke that is (1)parallel to the table, and (2)parallel to the line connecting the center of the cue ball with the center of the object ball. If you want to know how, ask Kato Lin. (HINT: It has something to do with the coefficient of friction)
Phil
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Matt
38 Posts |
Posted - 12/11/2007 : 11:18:48 AM
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Phil wrote: "By the way, this isn't the only clever way to avoid a double hit. I can do it with a HARD, FORWARD stroke that is (1)parallel to the table, and (2)parallel to the line connecting the center of the cue ball with the center of the object ball. If you want to know how, ask Kato Lin. (HINT: It has something to do with the coefficient of friction)"
I don't know anything about the coefficient of friction but I've used something along these lines before. You have to "measure" the exact amount of cue stick you need and then grip the back of the stick tightly so that the exact instant that the tip of the cue contacts the cue ball, the back hand contacts the edge of the table, thus stopping the momentum of the cue stick... |
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trhxke
USA
142 Posts |
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Torsten
USA
401 Posts |
Posted - 12/11/2007 : 3:47:38 PM
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Matt, wouldn't that hurt your hand? I've accidentally done that, and let me tell you, my pinky finger was not particularly thrilled with me.
Phil, coefficient of friction, huh? It's been a long time since I was in college but doesn't frictional coefficient assume that two objects bewteen which there is a coefficient are in contact, and not "very close". Either way, I'm not making much progress in trying to figure out the puzzle. Are we saying that the coefficient is static, since the balls are stationary before struck, or are we saying the coefficient is kinetic, since once the cue ball is struck they become in motion?
I think the worst time to have a heart attack would be during a game of charades... or during a game of fake heart attack. |
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Phil
USA
829 Posts |
Posted - 12/11/2007 : 3:54:13 PM
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quote:
[i]Originally posted by Matt[/i]
[br]Phil wrote: "By the way, this isn't the only clever way to avoid a double hit. I can do it with a HARD, FORWARD stroke that is (1)parallel to the table, and (2)parallel to the line connecting the center of the cue ball with the center of the object ball. If you want to know how, ask Kato Lin. (HINT: It has something to do with the coefficient of friction)"
I don't know anything about the coefficient of friction but I've used something along these lines before. You have to "measure" the exact amount of cue stick you need and then grip the back of the stick tightly so that the exact instant that the tip of the cue contacts the cue ball, the back hand contacts the edge of the table, thus stopping the momentum of the cue stick...
Close Matt, but that won't always work. It won't work when the cue ball is more than 4 1/2 feet or so down the table, such that the cue doesn't extend past the rail. Besides, there's still a chance that the cue ball will bounce back into the tip if you do it that way.
Phil
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Phil
USA
829 Posts |
Posted - 12/11/2007 : 3:57:07 PM
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quote:
[i]Originally posted by Torsten[/i]
[br]Matt, wouldn't that hurt your hand? I've accidentally done that, and let me tell you, my pinky finger was not particularly thrilled with me.
Phil, coefficient of friction, huh? It's been a long time since I was in college but doesn't frictional coefficient assume that two objects bewteen which there is a coefficient are in contact, and not "very close". Either way, I'm not making much progress in trying to figure out the puzzle. Are we saying that the coefficient is static, since the balls are stationary before struck, or are we saying the coefficient is kinetic, since once the cue ball is struck they become in motion?
I think the worst time to have a heart attack would be during a game of charades... or during a game of fake heart attack.
Both static and kinetic friction are involved...
Phil
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Torsten
USA
401 Posts |
Posted - 12/11/2007 : 4:41:14 PM
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In that case, I would venture to say that the kinetic friction would be the pool balls that are set in motion through contact of the cue to the white ball. The static friction would have to be that of the table felt on the balls, which causes deceleration. See, if I paid attention in physics (I got a B-minus), I might be able to figure this out...assuming ten years after the fact the info would be fresh in my head. Not gonna happen... But let's try.
First, can we assume that the cue ball is actually struck and that the strike causes the balls to go in motion, rather than some manipulation of static electricity gained by rapidly rubbing the cloth on the table?
I guess we would have to if the goal was to create a legal hit, thus avoiding a foul... Is the it the tip of the cue stick that is making contact with the white ball?
I think the worst time to have a heart attack would be during a game of charades... or during a game of fake heart attack. |
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Phil
USA
829 Posts |
Posted - 12/11/2007 : 5:09:27 PM
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quote:
[i]Originally posted by Torsten[/i]
[br]In that case, I would venture to say that the kinetic friction would be the pool balls that are set in motion through contact of the cue to the white ball. The static friction would have to be that of the table felt on the balls, which causes deceleration. See, if I paid attention in physics (I got a B-minus), I might be able to figure this out...assuming ten years after the fact the info would be fresh in my head. Not gonna happen... But let's try.
First, can we assume that the cue ball is actually struck and that the strike causes the balls to go in motion, rather than some manipulation of static electricity gained by rapidly rubbing the cloth on the table?
I guess we would have to if the goal was to create a legal hit, thus avoiding a foul... Is the it the tip of the cue stick that is making contact with the white ball?
I think the worst time to have a heart attack would be during a game of charades... or during a game of fake heart attack.
Normal stance, hard stroke, full follow through. No measuring or special props involved. Come on class, I gave you enough information in my first post to figure it out. Show me that you can apply what you've learned...
Phil
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Victor
USA
34 Posts |
Posted - 12/12/2007 : 05:07:04 AM
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If you all will bare with me for a moment (and yes, I do mean BARE), I'll try to simplify the coefficient theory of the "aerodynamically impacted" formulae. If you place the cue ball as stated in proximity to the object ball, then micronometrically gauging and multiplying the mass of the ass by the heat of the meat, divide the moan of the groan, then subtracting the bloat of the boat.
In algebraic terms:
(Cb + Ob x MA x HOM Ö m(of)g- BM= SDB)
Simply put: just shoot the damn ball!!
Professor Victor
BA, MS, BAMF |
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Kerry Randolph
USA
172 Posts |
Posted - 12/12/2007 : 1:34:48 PM
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All I can say is HOLY CRAP!
It is better to keep your mouth shut and appear stupid than to open it and remove all doubt |
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Torsten
USA
401 Posts |
Posted - 12/12/2007 : 2:37:53 PM
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I have to say, I'm stumped. I keep visualizing a normal shot in this situation with dual parallel lines and in my own head, each shot in which the cue ball is struck with the cue stick results in a double hit. The only thing I can think of is buildup of static electricity and then using a "hard, forward" stroke in extreme proximity to jostle the white ball into the object ball. But I can't imagine this making hard enough contact for something to subsequently make a rail. Care to enlighten us, Mr. Brooker?
I think the worst time to have a heart attack would be during a game of charades... or during a game of fake heart attack. |
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Phil
USA
829 Posts |
Posted - 12/12/2007 : 4:21:44 PM
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quote:
[i]Originally posted by Torsten[/i]
[br]I have to say, I'm stumped. I keep visualizing a normal shot in this situation with dual parallel lines and in my own head, each shot in which the cue ball is struck with the cue stick results in a double hit. The only thing I can think of is buildup of static electricity and then using a "hard, forward" stroke in extreme proximity to jostle the white ball into the object ball. But I can't imagine this making hard enough contact for something to subsequently make a rail. Care to enlighten us, Mr. Brooker?
I think the worst time to have a heart attack would be during a game of charades... or during a game of fake heart attack.
Hee hee - static electricity...
Not to overload the synapses of your cranial matter Torsten, but I can make the object ball travel the length of the table with this shot...
Phil
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Torsten
USA
401 Posts |
Posted - 12/13/2007 : 08:58:47 AM
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AHHHHHH! I asked you about that!!!! "First, can we assume that the cue ball is actually struck and that the strike causes the balls to go in motion, rather than some manipulation of static electricity gained by rapidly rubbing the cloth on the table?"
So do you generate the static electricity by rubbing your foot on the floor or what?
I think the worst time to have a heart attack would be during a game of charades... or during a game of fake heart attack. |
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