Mark Wilson's "additional friction" comment

EL'nino · Oct 29, 2015

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

) 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 · Oct 29, 2015

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 · Oct 29, 2015

EL'nino said:
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) 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 · Oct 29, 2015

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 · Oct 29, 2015

Wybrook said:
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.

alphadog said:
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 · Oct 29, 2015

alphadog said:
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".

frigopie said:
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 · Oct 29, 2015

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 · Oct 29, 2015

alphadog said:
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

cling/skid/kick

frozen-ball throw

Enjoy,
Dave

genomachino · Oct 29, 2015

100% correct on this.....

EL'nino said:
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) 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 · Oct 29, 2015

dr_dave said:
...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 · Oct 29, 2015

Patrick Johnson said:
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," (BD, August, 2014)

NV D.17 - Does a pool and billiards frozen combination throw more than a small-gap stun shot?

frozen throw resource page

Regards,
Dave

Patrick Johnson · Oct 29, 2015

genomachino said:
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 · Oct 29, 2015

dr_dave said:
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," (BD, August, 2014)

NV D.17 - Does a pool and billiards frozen combination throw more than a small-gap stun shot?

frozen throw resource page

Regards,
Dave

Thanks - I hadn't seen that.

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

SilverCue · Oct 29, 2015

Patrick Johnson said:
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 · Oct 29, 2015

SilverCue said:
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 · Oct 29, 2015

TOI-CTE-low deflection shaft-layered tip-Kamui chalk will overcome this problem.

Colonel · Oct 29, 2015

measureman said:
TOI-CTE-low deflection shaft-layered tip-Kamui chalk will overcome this problem.

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

measureman · Oct 29, 2015

Colonel said:
Don't forget the cool $1 bottle of water at Hanks.

I forgot that :banghead:

Skippy27 · Oct 29, 2015

As always Dr. Dave has not only the answer, but the evidence to show you why it is.

Cornerman · Oct 29, 2015

Patrick Johnson said:
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

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

Freddie

Mark Wilson's "additional friction" comment

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