Math Questions For Pool Players:

Bob Jewett

AZB Osmium Member
Staff member
Gold Member
Silver Member
OK, you are just fucking with us now, right?
Why do you restrict the question with the word "now"? ;)

To clear up some errors or sources of misunderstanding above....

If a cue ball is on a bare slate slab, the area of the contact patch is significant. If the cue ball is spinning in place, like a top, the major source of friction is the boring friction of the contact patch. If that circular patch really has zero radius, there will be zero boring friction because no torque can be applied with a zero-length lever arm.

The area of the contact patch on a cloth-covered table can be estimated by how quickly a spinning ball stops spinning and knowing the coefficient of sliding friction. Both of those are fairly easy to measure. The problem is complicated because the weight of the ball is distributed over the patch in a non-uniform way, so you end up with a tricky integral to do and a couple of assumptions to make. Also, spinning in place probably changes the coefficient of sliding friction during the spin. I think the result from a simple analysis will probably give you the area within a factor of two or so.

The patch is larger with thicker cloth. That's easy to see in the difference in spin-down times for fuzzy snooker cloth and very thin carom cloth.
 

JC

Coos Cues
Gold Member
Why do you restrict the question with the word "now"? ;)

To clear up some errors or sources of misunderstanding above....

If a cue ball is on a bare slate slab, the area of the contact patch is significant. If the cue ball is spinning in place, like a top, the major source of friction is the boring friction of the contact patch. If that circular patch really has zero radius, there will be zero boring friction because no torque can be applied with a zero-length lever arm.

The area of the contact patch on a cloth-covered table can be estimated by how quickly a spinning ball stops spinning and knowing the coefficient of sliding friction. Both of those are fairly easy to measure. The problem is complicated because the weight of the ball is distributed over the patch in a non-uniform way, so you end up with a tricky integral to do and a couple of assumptions to make. Also, spinning in place probably changes the coefficient of sliding friction during the spin. I think the result from a simple analysis will probably give you the area within a factor of two or so.

The patch is larger with thicker cloth. That's easy to see in the difference in spin-down times for fuzzy snooker cloth and very thin carom cloth.
Zero radius only exists in theory, not in our physical realm

Like I said math alone can't solve this and ..........................
 

justnum

Principal Investigator of Magic Trick Shots
Silver Member
Zero radius only exists in theory, not in our physical realm

Like I said math alone can't solve this and ..........................

Measuring RPMs on a table requires high speed camera.

I could use dummy values just to interpolate something close. However this is a math question for pool players.

Bob's answer is detailed enough to get working on it. Very different presentation than DrDave.
 

JC

Coos Cues
Gold Member
Measuring RPMs on a table requires high speed camera.

I could use dummy values just to interpolate something close. However this is a math question for pool players.

Bob's answer is detailed enough to get working on it. Very different presentation than DrDave.
It's not a math question it's a pant load of nonsense.

Are you really a teacher?

God help our youth.
 

justnum

Principal Investigator of Magic Trick Shots
Silver Member
.
You're a natural! ;) 😊

Its naming time.
The post presents the physical limits of the pool table.

I did the first conjecture towards generalizing the situation. Bob was the first to articulate the area of interest.

Main conclusion: Tangential contact between balls. However contact between ball and cloth is not tangential. Also the contact between cue ball and cue is not tangential.

If this was a math text than Bobs answer about uniform distributed forces and non uniform distributed forces fits perfectly.

To respond to DrDaves trivial case of "swerve". It would be like studying a black hole, estimations near singularities provide data difficult to observe.

If only one could come up with a way to measure data that is difficult to observe.
 

Icon of Sin

I can't fold, I need gold. I re-up and reload...
Silver Member
.


Its naming time.
The post presents the physical limits of the pool table.

I did the first conjecture towards generalizing the situation. Bob was the first to articulate the area of interest.

Main conclusion: Tangential contact between balls. However contact between ball and cloth is not tangential. Also the contact between cue ball and cue is not tangential.

If this was a math text than Bobs answer about uniform distributed forces and non uniform distributed forces fits perfectly.

To respond to DrDaves trivial case of "swerve". It would be like studying a black hole, estimations near singularities provide data difficult to observe.

If only one could come up with a way to measure data that is difficult to observe.
No one gives a shit...
 

Black-Balled

AzB Silver Member
Silver Member
No one gives a shit...
I know, right!

Hey- please keep this private, bcoz it is going to be HUGE. I am sure it will be a bigger boon for pool than tcom.

I am currently working very hard on paint colors for pool rooms and as you know, visuals are very important to humans and they can't get around seeing them and the influence they have on life- mood, ambiance, comfort, spending, etc...they are all intertwined and nobody has ever thought about colors before, as they pertain to pool.

I am so excited about how new colors will make pool bigger than it ever has been before and not only can you paint the walls inside, the list of things you can paint is almost endless, so you can start with the walls and then paint other things after that. You could even paint outside and then you could paint the floors too. It's going to be really big and it will make people want to play pool.

Take care and I will let you know when we can make the plan public
 

Maxx

AzB Platinum Member
Gold Member
Silver Member
.


Its naming time.
The post presents the physical limits of the pool table.

I did the first conjecture towards generalizing the situation. Bob was the first to articulate the area of interest.

Main conclusion: Tangential contact between balls. However contact between ball and cloth is not tangential. Also the contact between cue ball and cue is not tangential.

If this was a math text than Bobs answer about uniform distributed forces and non uniform distributed forces fits perfectly.

To respond to DrDaves trivial case of "swerve". It would be like studying a black hole, estimations near singularities provide data difficult to observe.

If only one could come up with a way to measure data that is difficult to observe.
(9 / 4.5)-reality= justnum
 

Texas Carom Club

play 1cushion & balkline
Silver Member
.


Its naming time.
The post presents the physical limits of the pool table.

I did the first conjecture towards generalizing the situation. Bob was the first to articulate the area of interest.

Main conclusion: Tangential contact between balls. However contact between ball and cloth is not tangential. Also the contact between cue ball and cue is not tangential.

If this was a math text than Bobs answer about uniform distributed forces and non uniform distributed forces fits perfectly.

To respond to DrDaves trivial case of "swerve". It would be like studying a black hole, estimations near singularities provide data difficult to observe.

If only one could come up with a way to measure data that is difficult to observe.

thanks alot bob
 

justnum

Principal Investigator of Magic Trick Shots
Silver Member
.
You're a natural! ;) 😊

Its naming time.

I did the first conjecture towards generalizing the situation. Bob was the first to articulate the area of interest.

Main conclusion: Tangential contact between balls. However contact between ball and cloth is not tangential. Also the contact between cue ball and cue is not tangential.

If this was a math text than Bobs answer about uniform distributed forces and non uniform distributed forces fits perfectly.

To respond to DrDaves trivial case of "swerve". It would be like studying a black hole, estimations near singularities provide data difficult to observe.
Probably the pool ball isn't even rotating until you observe it. It probably isn't even a particle but a wave...

I agree the compression forces at contact are wave forces. However for "miscues" the angle of impact plays a greater role in the demonstration of applied force.
 

Texas Carom Club

play 1cushion & balkline
Silver Member
Yes yes but the conglomerations of the event horizon are being completely disregarded in your toxic smoke screen
 

justnum

Principal Investigator of Magic Trick Shots
Silver Member
promoting pool as a way to discuss math and physics. im sure dave presented how physics can be manipulated.

however my focus is on creating more pool talk of the academic/art variety.

Unlike other people I am capable of coherent and didactic feedback.

thanks for keeping this thread alive.

if anyone wants more advanced thinking, consider if you line up three balls perfectly in a row and apply english on the first ball, how much is lost from beginning to end.

its the classic sliding versus tipping point question common to civil engineering and intro physics.

Just think in terms of rolling and activation energy needed for rolling.

I have enough puzzles for phd students. unfortunately for the retired academics, topics outside of the text can be intimidating.

thats what i am here for. Making sure no one acts like they know it all.
 

justnum

Principal Investigator of Magic Trick Shots
Silver Member
only you reserve that right i guess

better stick to scraping scum from bottom of toilets i think
i ask questions and start math discussions.

Please reread the thread title.

Your welcome to contribute the price of entry is articulation of math and physics in written English.

Its ok to say silly things nonlinear spaces are like that.
 

Texas Carom Club

play 1cushion & balkline
Silver Member
i ask questions and start math discussions.

Please reread the thread title.

Your welcome to contribute the price of entry is articulation of math and physics in written English.

Its ok to say silly things nonlinear spaces are like that.

Your welcome
 
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