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EL'nino
10-29-2015, 06:52 AM
Mark made the statement that when the cueball is close to an object ball it will impart "additional friction" onto that oblect ball so it will need to be "overcut". Does anyone know anything about this? How can an oblect ball (know:rolleyes:) how close the cue ball was when it was struck? Mark's knowledge of the game is well respected by many including myself but I would really like to hear more input about this before I consider it a fact.

alphadog
10-29-2015, 07:01 AM
I think it occrs because the cb is sliding not rolling when it strikes the object ball. Is a real phenomena.
Kind of like "skid,or snookers-kick".

Thomas McKane
10-29-2015, 07:06 AM
Mark made the statement that when the cueball is close to an object ball it will impart "additional friction" onto that oblect ball so it will need to be "overcut". Does anyone know anything about this? How can an oblect ball (know:rolleyes:) how close the cue ball was when it was struck? Mark's knowledge of the game is well respected by many including myself but I would really like to hear more input about this before I consider it a fact.

Closer hit on object ball means the cue ball is spinning less if using any english, which means less throw, which means more friction between cue ball and object ball.

Wybrook
10-29-2015, 07:30 AM
When you are real close to an OB and you put spin on the CB, more will grab because the CB is spinning more..

The spin on a CB becomes less and less as the CB travels further.. so in addition to any cut induced throw, you also have spin induced throw..

Try this, set up a ball close to CB and hit slow with a ton of inside.. You have to over cut the ball a ton.. As you move further away, you cut it less because there will be less spin on the CB at the time of contact.

frigopie
10-29-2015, 07:34 AM
When you are real close to an OB and you put spin on the CB, more will grab because the CB is spinning more..

The spin on a CB becomes less and less as the CB travels further.. so in addition to any cut induced throw, you also have spin induced throw..

Try this, set up a ball close to CB and hit slow with a ton of inside.. You have to over cut the ball a ton.. As you move further away, you cut it less because there will be less spin on the CB at the time of contact.

No, friction depends of velocity between surfaces, it's less with more velocity. Rolling velocity counts, if balls contact when one is rolling at high speed, friction is lower than if it were sliding. Touching balls are the ideal situation to maximize friction because they are not rolling at the moment of impact.

I think it occrs because the cb is sliding not rolling when it strikes the object ball. Is a real phenomena.
Kind of like "skid,or snookers-kick".

I agree.

BasementDweller
10-29-2015, 07:47 AM
I think it occrs because the cb is sliding not rolling when it strikes the object ball. Is a real phenomena.
Kind of like "skid,or snookers-kick".

No, friction depends of velocity between surfaces, it's less with more velocity. Rolling velocity counts, if balls contact when one is rolling at high speed, friction is lower than if it were sliding. Touching balls are the ideal situation to maximize friction because they are not rolling at the moment of impact.



I agree.


I think he's referring to the sliding cue ball like frigopie noted. The only thing different about the balls being close together is that you can assume that the cue ball will ALWAYS be sliding, whereas when the balls are further apart you can't be as certain.

I could be wrong and the experts will be along shortly.

jsp
10-29-2015, 08:39 AM
The distance between CB and OB, by itself, has nothing to do with the amount of throw. The relative surface speeds at impact, given a fixed set of ball conditions (dirty, clean, polished, etc.), is what dictates throw. Generally the higher the surface speeds at impact, the less throw you'll have.

It's just that the closer the CB is to the OB, the more likely the OB will not achieve natural forward roll when it hits the OB. For a given CB transnational velocity (the horizontal speed the OB travels across the table), the more forward roll the CB has the higher the relative surface speeds at impact, and thus the less throw you'll experience.

But that doesn't mean you can't achieve natural forward roll at very close CB and OB distances, because you can depending on how high above the equator the CB is hit. Above a certain point (2/5 * R), the CB will achieve natural forward roll instantly.

dr_dave
10-29-2015, 08:49 AM
I think it occrs because the cb is sliding not rolling when it strikes the object ball. Is a real phenomena.
Kind of like "skid,or snookers-kick".That is correct. When the CB is close to an OB (and top or bottom spin is not used), or when an OB is close to or frozen to an OB in a combination shot, there will be more throw than normal because the first ball is hitting the second ball with stun, where throw is maximum (especially at slow speed). Some people mistakenly call this cling, skid, or kick, which is a exceesive amount of throw well above the expected amount for a given shot.

If there happens to be a chalk mark at the ball-ball contact point, then there will be cling/skid/kick, and the amount of throw will be "through the roof" with this type of shot.

For more information and demonstrations, see:

maximum throw (http://billiards.colostate.edu/threads/throw.html#maximum)

cling/skid/kick (http://billiards.colostate.edu/threads/throw.html#cling)

frozen-ball throw (http://billiards.colostate.edu/threads/throw.html#frozen)

Enjoy,
Dave

genomachino
10-29-2015, 08:57 AM
Mark made the statement that when the cueball is close to an object ball it will impart "additional friction" onto that oblect ball so it will need to be "overcut". Does anyone know anything about this? How can an oblect ball (know:rolleyes:) how close the cue ball was when it was struck? Mark's knowledge of the game is well respected by many including myself but I would really like to hear more input about this before I consider it a fact.

Most of the better players understand this for sure. If you don't your going to miss too many shots to get to any type of higher level.

Patrick Johnson
10-29-2015, 09:01 AM
...when an OB is close to or frozen to an OB in a combination shot, there will be more throw than normal because the first ball is hitting the second ball with stun, where throw is maximum (especially at slow speed).
There's also a difference between a sliding CB that's moving at contact and one that's frozen to the OB (kinetic vs. static friction), right? I believe static friction (frozen balls) is greater. Do we know the amount of difference?

pj
chgo

dr_dave
10-29-2015, 09:09 AM
There's also a difference between a sliding CB that's moving at contact and one that's frozen to the OB (kinetic vs. static friction), right? I believe static friction (frozen balls) is greater. Do we know the amount of difference?Actually, in careful tests I have done, a purely sliding CB throws very nearly the same amount (the same amount, for all practical purposes) as a frozen combo struck at the same speed. For more info and demonstrations, see:

"Throw Follow-up: Part II: More Results (http://billiards.colostate.edu/bd_articles/2014/july14.pdf)," (BD, August, 2014)

NV D.17 - Does a pool and billiards frozen combination throw more than a small-gap stun shot? (http://billiards.colostate.edu/normal_videos/new/NVD-17.htm)

frozen throw resource page (http://billiards.colostate.edu/threads/throw.html#frozen)

Regards,
Dave

Patrick Johnson
10-29-2015, 09:28 AM
Most of the better players understand this for sure. If you don't your going to miss too many shots to get to any type of higher level.
A sidebar:

I'd think that any better player knows this, but probably not the reason for it (sliding vs. rolling CB). So they may not realize that a sliding CB from a greater distance creates the same amount of throw.

This is a good example of why it's good to know "the science" - what's actually happening - vs. what appears to be happening based on one instance.

pj
chgo

Patrick Johnson
10-29-2015, 09:31 AM
Actually, in careful tests I have done, a purely sliding CB throws very nearly the same amount (the same amount, for all practical purposes) as a frozen combo struck at the same speed. For more info and demonstrations, see:

"Throw Follow-up: Part II: More Results (http://billiards.colostate.edu/bd_articles/2014/july14.pdf)," (BD, August, 2014)

NV D.17 - Does a pool and billiards frozen combination throw more than a small-gap stun shot? (http://billiards.colostate.edu/normal_videos/new/NVD-17.htm)

frozen throw resource page (http://billiards.colostate.edu/threads/throw.html#frozen)

Regards,
Dave
Thanks - I hadn't seen that.

pj <- learned something - it's a good day
chgo

SilverCue
10-29-2015, 09:40 AM
A sidebar:

I'd think that any better player knows this, but probably not the reason for it (sliding vs. rolling CB). So they may not realize that a sliding CB from a greater distance creates the same amount of throw.

This is a good example of why it's good to know "the science" - what's actually happening - vs. what appears to be happening based on one instance.

pj
chgo

Not really, because at greater distances, the cue ball is usually traveling faster for stun.
And as Dr Dave pointed out, the slower stun causes more throw.

Al

Patrick Johnson
10-29-2015, 09:50 AM
Not really, because at greater distances, the cue ball is usually traveling faster for stun [faster = less throw].
Depends on how far away and how far you want the CB to travel after contact - it could even be slower from a greater distance.

The important thing is the "scientific" principle - so you'll know what to expect across the range of possibilities.

pj <- but speed is a factor
chgo

measureman
10-29-2015, 12:57 PM
TOI-CTE-low deflection shaft-layered tip-Kamui chalk will overcome this problem.

Colonel
10-29-2015, 01:03 PM
TOI-CTE-low deflection shaft-layered tip-Kamui chalk will overcome this problem.


Don't forget the cool $1 bottle of water at Hanks. [emoji6]

measureman
10-29-2015, 01:10 PM
Don't forget the cool $1 bottle of water at Hanks. [emoji6]

I forgot that :banghead:

Skippy27
10-29-2015, 01:11 PM
As always Dr. Dave has not only the answer, but the evidence to show you why it is.

Cornerman
10-29-2015, 01:12 PM
There's also a difference between a sliding CB that's moving at contact and one that's frozen to the OB (kinetic vs. static friction), right? I believe static friction (frozen balls) is greater. Do we know the amount of difference?

pj
chgoOnly at very high speeds. For most shots seen on a pool table, kinetic and static friction are nearly the same.

Freddie

measureman
10-29-2015, 01:13 PM
As always Dr. Dave has not only the answer, but the evidence to show you why it is.

that's true.
He is here in Colorado and I wonder if he's ever had a bottle of "Hanks" $1 water?

Patrick Johnson
10-29-2015, 01:29 PM
Only at very high speeds. For most shots seen on a pool table, kinetic and static friction are nearly the same.

Freddie
Thanks, Freddie.

pj
chgo

JayKidd
10-29-2015, 05:35 PM
I think what you said may be very accurate for most common ball-ball collisions on pool tables, but in general they can be quite different, e.g. kinetic vs. static frictions between ball and cloth, between cuetip and ball.

Only at very high speeds. For most shots seen on a pool table, kinetic and static friction are nearly the same.

Freddie

dr_dave
10-30-2015, 07:10 AM
Only at very high speeds. For most shots seen on a pool table, kinetic and static friction are nearly the same.The physics of throw is not a simple matter of kinetic vs. static friction. With a frozen CB or a frozen-OB combination, one might think "static" friction applies. However, there is still sliding between the balls during contact. If the cut angle between the balls is on the small side (less than about 20 degrees), sliding stops during contact and the balls "gear" together. In this case, the amount of throw doesn't vary at all with shot speed. For larger cut angles (greater than about 20 degrees), where sliding occurs during the entire contact period, the amount of throw is less at faster speeds because the effective "kinetic" friction is less at faster relative surface speeds.

FYI, items 16-27 in the numbered list on the squirt/swerve/throw effects resource page (http://billiards.colostate.edu/threads/aiming.html#English_effects) summarize all throw effects (with supporting articles and demonstrations). If you look at this list, it is clear that throw is not a simple matter of "static" vs. "kinetic" friction.

For those interested in the math and physics details, they are presented in TP A.14 - The effects of cut angle, speed, and spin on object ball throw (http://billiards.colostate.edu/technical_proofs/new/TP_A-14.pdf). The articles linked from the squirt/swerve/throw effects resource page (http://billiards.colostate.edu/threads/aiming.html#English_effects) attempt to present and illustrate the results of the analysis and supporting experiments in simple terms with examples.

Check it out,
Dave