Push Shot vs. Double Hit

[Cory in DC]

. e.g. A shot I used to like to play was the push through with draw, such that the CB would go through the ball 12 inches and then stop in position for the next ball.

Say the CB is 1/2 chalk away from the OB. Hit with heavy elevation, would most here call this a bad hit? Is it that the cue stick is hitting the CB twice, with the second hit pushing it forward, and then the backspin from the elevation kicks in and the CB stops 8-12" from the OB? If so, that would seem to definitely be a bad hit.

On the other hand, it seems possible that the CB is bouncing, forward, due to the elevation of the cue and the contact with the OB. Then when it stops bouncing, the backspin makes it stop. This would seem to be a good hit.

Cory

 

[The Kiss]

Jacking up doesn't guarantee anything. Is it possible that you also don't understand the definitions?

Fred

No jacking up puts automatic backspin on the ball( hence no foul)....Sure you could still foul while jacked up and or double hit it...But your need of recognition to call a foul in just silly...Your point of how well you understand the rules vs. what everyone else understands is comical...Either Foul is clearly recognized by any experienced shooter ....Either you double hit the cue ball, or push the ball vs. stroke it... What's to not understand....Ball in hand for me

 

[Cornerman]

.Your point of how well you understand the rules vs. what everyone else understands is comical

What exactly is the point of this statement? It is obvious that not everyone understand these two rules. Now what? Nobody gets to clear out the definitions? My point has nothing to do with the fact that I understand the rules.

Either Foul is clearly recognized by any experienced shooter

Right. Nobody argues these fouls. I thought you said you were experienced. Every experienced shooter has come across these arguments in tournaments regarding what is a foul or not. Puleeeeze.

....Either you double hit the cue ball, or push the ball vs. stroke it... What's to not understand....Ball in hand for me

There's nothing else to understand. If you already understand it, then you have no reason to continue reading it or responding. For those that don't understand it, they should have an opportunity to read. Since you keep saying "experienced shooter," then the inexperienced shooter should be welcomed to read this thread.

And, btw, as I've said before, many professionals don't understand the rules. Are you more experienced than they?

Fred <~~~ pretty damned experienced

 

[mikepage]

The problem is how can you actually differentiate between a legal shot and a push shot, considering that all legal shots are technically "pushed" by the cue tip to a certain degree. After all, the impact between cue and CB is not exactly one instant in time, but rather the CB is pushed by the tip in the order of a millisecond or two. [...]

I don't think there's a practical problem here. I just wish the "push shot" would be renamed to some obscure hard-to-pronounce French word. I think most of the confusion would go away.

I think if you analyzed all shots (players and bangers) over an entire year in a poolroom, here is a plausible distribution of shots:

[12 tables going on average five hours a day at 100 shots per hour per table]

TOTAL # SHOTS: 2,200,000
TOTAL # MISCUES 40,000
TOTAL # NON-MISCUE DOUBLE HIT FOULS: 10,000
TOTAL # SHOTS THAT BREAK A LIGHTBULB: 3
TOTAL # PUSH SHOT FOULS: 2

mike page
fargo

 

[jsp]

A push shot is a shot where you push the cueball. That's pretty specific. I think we all know the difference between, say, pushing a chair and hitting a chair.

But, physics speaking, for a push, both the objects in question have to leave the initial collision in contact and at the same velocity for a time longer than simple compression dynamics. That is, there is an additional pushing force that affects the contact during contact, whereas in a non-push, no additional force affects the contact.

In a collision that is not a push, the cue tip has a non-zero velocity before the contact. At contact, the cue tip is rapidly decelerating, and the object ball is rapidly accelerating. That collison can be express in a straight-forward conservation of energy and momentum. I don't think a push can be expressed in those terms, but instead a force*distance term.

I'd like to defer to better physics authorities to provide a more concise definition.

The volleyball analogy is a good one.

Fred

Yes, you're right. I agree there is a fundamental difference in the physics between a legal hit and a push shot. My point was that it's very difficult to tell one from the other when stroking through two frozen balls. But I guess it's not extremely difficult to distinguish the two considering what poolboy17 said...

Most of the time when someone illegally pushes the cueball on frozen balls...you get what refs sometimes refer to as "the slide". IMHO, it's not the most difficult call to get right.

I'll take your word for it, considering I'm not an IPT referee.

As for the physics...

I think that for a legal hit, the CB leaves the cue during the cue's deceleration phase after impact. Just prior, the CB is rapidly accelerating from zero velocity while the cue is rapidly decelerating. At some point, the tip velocity becomes less than the CB velocity, and at that moment the impact time is over.

For a push, there is another phase of acceleration and deceleration of the cue. On initial impact, the cue rapidly decelerates, but not great enough for the CB's velocity to overtake the cue tip (but maybe the CB's velocity overtakes the cue velocity, such that a double hit occurs). After this quick deceleration phase, the cue then accelerates again, such that the cue "pushes" the CB and both would have the same velocity for a certain amount of time. Eventually, the cue decelerates a second time and the CB maintains its velocity, such that the extended impact time is over.

...at least I think that's what happens.

EDIT: Sorry Fred, but I think I just regurgitated exactly what you said regarding the physics. I wasn't paying too much attention the first time I read it.

 

[Cornerman]

I don't think there's a practical problem here. I just wish the "push shot" would be renamed to some obscure hard-to-pronounce French word. I think most of the confusion would go away.

I nominate "poussé." Nobody would dare say it to a woman.

I think if you analyzed all shots (players and bangers) over an entire year in a poolroom, here is a plausible distribution of shots:

[12 tables going on average five hours a day at 100 shots per hour per table]

TOTAL # SHOTS: 2,200,000
TOTAL # MISCUES 40,000
TOTAL # NON-MISCUE DOUBLE HIT FOULS: 10,000
TOTAL # SHOTS THAT BREAK A LIGHTBULB: 3
TOTAL # PUSH SHOT FOULS: 2

mike page
fargo

Great stuff, but if you count hitting the light bulb when you raise your stick after a shot, then that number is horrendously low.

Fred

 

[The Kiss]

What ever keep up your own pretzel logic so you look good in your mind...

Your original statement was no one understand the rules...Which is untrue...Then you say a Pro does'nt know the rules..So thats his problem...But I could'nt possibly know more than a pro???? Is it possible my ability to read could far supercede a Pros???

You play in a tournament you get the director any seasoned player knows that....

Yeah I'll agree with you a lot of people don't know the rules for a lot of games....But don't make it sound like your the only one who can read and interpret the rules....You condescending _______...

 

[Williebetmore]

Exactly Opposite. The high speed video showed that a shot directly at a frozen pair is a single hit.

Fred

Fred,
I guess I'm remembering this discussion wrong (from some magazine). I thought for sure they said that some part of the ferrule or shaft (not the tip though) also touched the cue ball on a high percentage of these shots. Would the video's themselves be available at Dr. Dave's site (perhaps second hand info is not the best)???

 

[Cornerman]

Fred,
I guess I'm remembering this discussion wrong (from some magazine). I thought for sure they said that some part of the ferrule or shaft (not the tip though) also touched the cue ball on a high percentage of these shots. Would the video's themselves be available at Dr. Dave's site (perhaps second hand info is not the best)???

First hand information from Bob Jewett should suffice:

Bob Jewett's Answer to: How many hits on a frozen pair?

Fred

 

[Bob Jewett]

This comes up once a year, so I'll try it again. ...

The RSB FAQ does its best to differentiate between double hits and push shots. http://www.sfbilliards.com/faq.html

My January 2006 article in Billiards Digest proposes the "one stroke" rule and shows several problematic shots.

I think Colin has seen no problem yet because the English-eight-ball players have not figured out what the rules permit them to do. The rule seems to be if the referee thinks he can see a second hit or hear a second hit, the double hit is a foul.

I refereed once under the rule, "If the referee cannot actually see the tip hit the cue ball a second time, there is no foul." I think that's a lousy rule. Unfortunately the alternative requires the players and referees to understand double hits, and that may never happen.

 

[RBC]

I tend to agree that this topic needs some discussion. That is the only way the many folks out there that confuse these two will learn the difference without having to learn it the hard way in a real game. And there are a large number of them.

Double hits:
Unfortunately, some of the "experienced" players will see the double hit foul coming and either not say anything and call a foul after the less experienced has shot, or get a ref to watch the shot and not explain anything to the lesser player. I like to mention to the lesser player the possibility of a double hit and explain it to him or her. That way they learn about the rules and still have an opportunity to make a good decision. After all, if they are the lesser player and I am the more experienced player, I still have the advantage. Most sets are not won or lost on one shot.

Push fouls:
I think we are talking around things when we talk about how long the tip stays in contact with the cueball. I mean yes that is the result of the push, but the best way to tell is to watch the speed at which the cue comes in contact with the cueball. If a player is accelerating his cue as normal, there is no possible way to "push" the cueball. The only way to "push" the cueball is to basically touch the tip to the cueball and then accelerate both of them together. Anytime a collision takes place between the tip and the cueball, there can be no push because the cueball rebounds from the collision away from the the tip.

Just my thoughts

Royce
www.obcues.com

 

[ironman]

A good analogy would be that a push shot is similar to a lift in volleyball. Basically the tip stays in contact with the cueball for an extended period of time as opposed to hitting it two or more times.

Good analogy. I like that.

 

[ironman]

Thats like saying when a cue ball jumps off the table...Do you really need to go into specifics to know its a foul??? Any seasoned player knows its a foul...Some rookie or just a moron might need it explained....Thats why if we are playing for cash we tell the guy to jack up..then he knows a foul is coming if he does'nt...A double hit is generally given away by the sound, or if the guy does'nt jack up in tight quarters...A push is generally obvious by the follow thru in a the same tight quarters

If at the DCC and Buddy happens to come aound, set em upu and watch him hit'em. He either gets away with it better, or just hits those shots better than anyone who ever lived.

 

[ironman]

I don't think there's a practical problem here. I just wish the "push shot" would be renamed to some obscure hard-to-pronounce French word. I think most of the confusion would go away.

I think if you analyzed all shots (players and bangers) over an entire year in a poolroom, here is a plausible distribution of shots:

[12 tables going on average five hours a day at 100 shots per hour per table]

TOTAL # SHOTS: 2,200,000
TOTAL # MISCUES 40,000
TOTAL # NON-MISCUE DOUBLE HIT FOULS: 10,000
TOTAL # SHOTS THAT BREAK A LIGHTBULB: 3
TOTAL # PUSH SHOT FOULS: 2

mike page
fargo

Mike, you and Colin should hang out a while. you guys have entirely too much time on your hands.