Sidespin on a stopshot

[Williebetmore]

where did "we" come from. is there a group of azers behind you and you asked them "can I speak for you guys," and they said yes? doubt it. unbeknownst to you this thread has more to do with cueball movement than you may ever be able to comprehend. you really need to be able to read and understand the threads before you come in with an arrogant post. i mean really, who do you think you are to decide what is interesting enough to warrant discussion by others, that is for them to decide? notice, there are 2 pages of replies.

in any case, if you really aren't interested, just don't open the thread anymore. if you do anything other than that it proves you just want to argue.

thanks.

Zo-man,
Just asking a question about why we forum members should be interested - not speaking for anyone. In case you are unaware, you have been somewhat mysterious about your intentions in opening the thread.

No arrogance here, I just want to know ( and just want to have as much fun doing it as possible; sorry if you took it the wrong way ). If you'd rather not say that's your prerogative.

 

[enzo]

Zo-man,
Just asking a question about why we forum members should be interested - not speaking for anyone. In case you are unaware, you have been somewhat mysterious about your intentions in opening the thread.

No arrogance here, I just want to know ( and just want to have as much fun doing it as possible; sorry if you took it the wrong way ). If you'd rather not say that's your prerogative.

you're right, that's a good question (about my intention i mean).

i just think regarding this sort of thing there are a lot of misconceptions, and i was really just curious to see how common those misconceptions are.

as to why azers should be interested. i believe that one of the keys to understanding and thus controling very subtle, short (one or two inches) cueballs movements lies in english and its impacts on these movements.

 

[Williebetmore]

as to why azers should be interested. i believe that one of the keys to understanding and thus controling very subtle, short (one or two inches) cueballs movements lies in english and its impacts on these movements.

Zo,
Thanks for the explanation; I think it's a very good topic, and that "we" SHOULD be interested. Sorry if my post was poorly worded (I KNEW I should have gotten more sleep last night - too busy practicing pool).

 

[Scott Lee]

i just think regarding this sort of thing there are a lot of misconceptions, and i was really just curious to see how common those misconceptions are.

You're certainly right about how common misconceptions about many strokes and shots are. Just look at the poll...more than half believe that the CB will move sideways...when in fact, it will NOT.

Scott Lee
www.poolknowledge.com

 

[mikepage]

You're certainly right about how common misconceptions about many strokes and shots are. Just look at the poll...more than half believe that the CB will move sideways...when in fact, it will NOT.
[...]

OK everybody now.

Reach down and grab the chair you're sitting on from underneath. Now pull up hard.... Lift the chair off the ground. Harder... Harder... Surely somebody is strong enough to lift himself up this way...

When someone shows me the person who can lift himself up like this, THAT's when I will stop believing Newton's third law and believe the above instead.

mike page
fargo

 

[jsp]

You're certainly right about how common misconceptions about many strokes and shots are. Just look at the poll...more than half believe that the CB will move sideways...when in fact, it will NOT.

Scott Lee
www.poolknowledge.com

Scott, are you assuming completely frictionless balls?

 

[Peer]

Williebetmore wrote:
> I think the real question is why on earth we would care??
> I can see why we would be concerned about the direction/throw
> of the object ball or about the path of the cue ball after
> contact; but who really cares about whitey's spin if its stopped

Enzo replied:
> where did "we" come from. is there a group of azers
> behind you and you asked them "can I speak for you guys,"


Yes, he has a group behind him -- in fact, our club "We Don't Care about the Whitey" meet once a month to discuss this issue and how little we care. It's for members only.

-- peer

 

[mnShooter]

You're certainly right about how common misconceptions about many strokes and shots are. Just look at the poll...more than half believe that the CB will move sideways...when in fact, it will NOT.

Scott Lee
www.poolknowledge.com

So your saying there will be absolutely no curve/swerve to the cueball on the way to the object ball?

 

[Colin Colenso]

It's actually possible to use left english to pot a straight in shot and make the CB move slightly right after hitting the OB. But on this shot you are actually hitting the OB right of the point along the line through the balls to the pocket. The left spin throws the OB to the right.

But as the question was stated. If the CB and OB contact at the points along the straight line, the CB will move slightly left. It's a proven and well known effect.

Colin

 

[Bob Jewett]

... If the CB and OB contact at the points along the straight line, the CB will move slightly left. It's a proven and well known effect. ...

Evidently Mike Sigel and the unknownpro are unaware of this. And I wonder of Randy and Scott were pulling our collective leg. Spitting on the object ball is not allowed.

 

[unknownpro]

Evidently Mike Sigel and the unknownpro are unaware of this. And I wonder of Randy and Scott were pulling our collective leg. Spitting on the object ball is not allowed.

I'm aware that if I hit that shot I do not allow for throw. Can it throw? Sure. Does it always throw enough to be measured, or see the effect? I don't think so. In fact I think the shot is just as easy with the sidespin, as opposed to hitting center ball, because any slight offset from center ball can throw the object ball more than the spinning cueball.

On the frozen rail shot do you think you have to aim for more rail when using inside as opposed to center ball?

Do you think like I do that inside english produces generally much less throw than outside or center ball? If so, what is your explanation, and why couldn't this effect contribute to minimizing the throw to near zero on a straight shot?

unknownpro

 

[Skeezicks]

Of course some people might have an operational definition of "full hit" as a contact that leads to no sideways cueball motion. If so, then a full hit with side spin leads to no cueball sideways motion by definition...

I read this question as: When two balls collide such that the line of centers at the moment of contact is parallel to the direction of the cue ball's travel (full ball hit) and the cue ball has stun side spin, does the cue ball stop dead (and spin) or move ever so slightly to the side (and spin)?

 

[mikepage]

I read this question as: When two balls collide such that the line of centers at the moment of contact is parallel to the direction of the cue ball's travel (full ball hit) and the cue ball has stun side spin, does the cue ball stop dead (and spin) or move ever so slightly to the side (and spin)?

Yes, I think this is the intended question.

Here are the physical principles involved.

When the above collision happens, say with left spin, the object ball will be thrown to the right. If the object ball gets pushed to the right , then whatever pushed it (the cue ball here) gets pushed to the left with the same force. This is Newton's Third Law. (Every action has an equal and opposite reaction).

A consequence of Newton's Third Law is the Conservation of Momentum. The way you apply that here is to compare the total sideways momentum just before the collision to the total sideways momentum just after the collision. They MUST be the same.

With the full hit described above, the total sideways momentum just before the collision is zero (nothing moving to the left and nothing moving to the right). Just after the collision, we see the object ball angling off to the right a bit. So there is some small component of the object ball's velocity that is "to the right" and thus a small amount of momentum (ball mass times this velocity component). Conservation of momentum demands there be a canceling momentum to the left. We know this because the total sideways momentum must be zero, as it was before the collision. So the cueball will be moving to the left with the same speed as the sideways component of the object ball's speed.

BUT BUT BUT ....

We have all seen a cueball stop dead with spin *and* an object ball throw to the right! Anyone who plays straight pool knows he can stop a cueball dead and throw an object ball. What's the deal? Is the physics described above only kinda right? Or only right in an idealized world? Or does it require elastic collisions or some such thing?

---NO, the physics described above is completely right and always right.

The deal is that on those shots we've done and seen, the cueball is always close to the object ball. And if you look carefully, to throw the object ball to the right stopping the cueball with spin, we are actually cutting the object ball to the left a bit--just enough to counteract the cueball's tendency to move left because of the throw. And the object ball still throws to the right.

So after the collision there is net sideways momentum to the right (cueball is still and object ball is movng to the right). There must have been net sideways momentum to the right before the collision! There was. Recall the cueball was struck slightly to the right to create a small cut angle.

This shot cannot be done with the cueball too far away from the object ball.

mike page
fargo

 

[Tennesseejoe]

Evidently Mike Sigel and the unknownpro are unaware of this. And I wonder of Randy and Scott were pulling our collective leg. Spitting on the object ball is not allowed.

Spitting on the cue ball may miminize friction and its effect but not eliminate it.

 

[Bob Jewett]

... Do you think like I do that inside english produces generally much less throw than outside or center ball? If so, what is your explanation, and why couldn't this effect contribute to minimizing the throw to near zero on a straight shot?...

I think that for inside english, you are already used to compensating for collision-induced throw so the added (if any) throw from the inside english is smaller. In fact, if Marlow and Alciatore are right, and friction decreases with increasing slip speed, inside english could conceivably reduce throw below the amount due to collision-induced throw.

As for whether throw is significant on most shots, I think it is. And I think most people adjust for it subconsciously and just do what feels right to put the ball in the pocket.

 

[supergreenman]

Spitting on the cue ball may miminize friction and its effect but not eliminate it.

Dear Mr. Opponent please do not call a foul on me for spitting on the ball. You see I want to minimize the friction.

 

[Bob Jewett]

Dear Mr. Opponent please do not call a foul on me for spitting on the ball. You see I want to minimize the friction.

No, no, no! You simply ask if it's OK to clean the cue ball as there is mung on it. Make sure that a finger is previously wetted, and keep that wet finger in reserve until it is time to place the cue ball back on the table. Look nonchalant.

 

[zeeder]

You're certainly right about how common misconceptions about many strokes and shots are. Just look at the poll...more than half believe that the CB will move sideways...when in fact, it will NOT.

Scott Lee
www.poolknowledge.com

I guess it depends on your definition of "slightly". Friction will cause the ball to move left, as well as the object ball to move right. The degree to which this happens depends on how clean, or dirty, the balls are at the contact point.

 

[Purdman]

No, no, no! You simply ask if it's OK to clean the cue ball as there is mung on it. Make sure that a finger is previously wetted, and keep that wet finger in reserve until it is time to place the cue ball back on the table. Look nonchalant.

Hey Bob, tell em where to stick that finger to keep it wet!
Purdman

Anybody want to play switch?

 

[ShaneT58]

Yes, I think this is the intended question.

Here are the physical principles involved.

When the above collision happens, say with left spin, the object ball will be thrown to the right. If the object ball gets pushed to the right , then whatever pushed it (the cue ball here) gets pushed to the left with the same force. This is Newton's Third Law. (Every action has an equal and opposite reaction).

A consequence of Newton's Third Law is the Conservation of Momentum. The way you apply that here is to compare the total sideways momentum just before the collision to the total sideways momentum just after the collision. They MUST be the same.

With the full hit described above, the total sideways momentum just before the collision is zero (nothing moving to the left and nothing moving to the right). Just after the collision, we see the object ball angling off to the right a bit. So there is some small component of the object ball's velocity that is "to the right" and thus a small amount of momentum (ball mass times this velocity component). Conservation of momentum demands there be a canceling momentum to the left. We know this because the total sideways momentum must be zero, as it was before the collision. So the cueball will be moving to the left with the same speed as the sideways component of the object ball's speed.

BUT BUT BUT ....

We have all seen a cueball stop dead with spin *and* an object ball throw to the right! Anyone who plays straight pool knows he can stop a cueball dead and throw an object ball. What's the deal? Is the physics described above only kinda right? Or only right in an idealized world? Or does it require elastic collisions or some such thing?

---NO, the physics described above is completely right and always right.

The deal is that on those shots we've done and seen, the cueball is always close to the object ball. And if you look carefully, to throw the object ball to the right stopping the cueball with spin, we are actually cutting the object ball to the left a bit--just enough to counteract the cueball's tendency to move left because of the throw. And the object ball still throws to the right.

So after the collision there is net sideways momentum to the right (cueball is still and object ball is movng to the right). There must have been net sideways momentum to the right before the collision! There was. Recall the cueball was struck slightly to the right to create a small cut angle.

This shot cannot be done with the cueball too far away from the object ball.

mike page
fargo

I'm thinking along these lines also but I believe its more complicated than that because you have angular momentum from the spinning balls to account for as well.