Physics Questions on "sliding" as it relate to pool balls.

[ENGLISH!]

Dave,

Thanks for the info & vids & again for your devotion. Billiards is very much a game of minutes. I noticed the words 'fairly straight' & 'perfectly straight' used in the same video. I certainly do not want to be a 'contrarian' as PJ says that I am, but I have hard time 'believeing' that a ball rolling perfectly around its horizontal axis & one rolling around a diagonal axis will have the exact same outcome. I would uderstand that if it were out in space with nothing for the spin to grab. But on a cloth with gravity? What am I missing?

Thanks again,

 

[dr_dave]

Dave,

Thanks for the info & vids & again for your devotion. Billiards is very much a game of minutes. I noticed the words 'fairly straight' & 'perfectly straight' used in the same video. I certainly do not want to be a 'contrarian' as PJ says that I am, but I have hard time 'believeing' that a ball rolling perfectly around its horizontal axis & one rolling around a diagonal axis will have the exact same outcome. I would uderstand that if it were out in space with nothing for the spin to grab. But on a cloth with gravity? What am I missing?

Thanks again,

You certainly are a "contrarian" (and even a "pain in the ass" at times :wink, but I like your relentless drive to find answers that make sense.

Actually, a ball rolling forward with sidespin is predicted by physics to have an extremely small drift, but it is much too small to be noticeable or important. More info, a complete explanation, and the detailed physics analysis, can be found here:

ball "turn" resource page​

Regards,
Dave

 

[JoeyA]

I think the definitions and interpretations depend on who you are talking to in the "pool world." I personally believe the following definitions (from my online glossary) are consistent with both a physics understanding and how most of the "pool world" describes things:

natural roll: rolling motion of a ball where there is no sliding between the ball and the table cloth.

sliding: relative motion between the bottom of a moving ball and the cloth resulting in friction. Sliding occurs any time the ball is not rolling naturally.

skid: term used to describe the sliding motion of an object ball due to throw or cling.

stun shot: a shot where the cue ball has no top or bottom spin (i.e., it is purely sliding) when hits the object ball. A stun shot is also called a “stop shot at an angle.”​

I probably won't be changing these, but thank you for the suggestion. :wink:

Regards,
Dave

PS: You apparently didn't get the answer you wanted in this thread. You should do a little more research the next time you make a bet.

That's all right. You science guys will eventually get it right.

 

[ENGLISH!]

You certainly are a "contrarian" (and even a "pain in the ass" at times :wink, but I like your relentless drive to find answers that make sense.

Actually, a ball rolling forward with sidespin is predicted by physics to have an extremely small drift, but it is much too small to be noticeable or important. More info, a complete explanation, and the detailed physics analysis, can be found here:

ball "turn" resource page​

Regards,
Dave

Ahhh, 'extremely small drift' but 'too small to be noticeable or important'. Maybe to you, but not to me.

Thanks again, & I'm sorry for being a royal pain in the ass, but inquiring 'minds' want to know the absolutes.

Best Regards,

 

[LWW]

That's all right. You science guys will eventually get it right.

The only thing DrDave was off was that all the scenarios he described involve friction ... which is simply converting energy to heat.

 

[dr_dave]

Ahhh, 'extremely small drift' but 'too small to be noticeable or important'. Maybe to you, but not to me.

I think you are missing a very important point. The effect is so small that even a tiny piece of dirt or a slight irregularity in the cloth can have a much larger effect. That should give you a better feel for how insignificant "ball turn" truly is. Even a "contrarian" should be able to recognize this (especially if you watch the videos and/or do some careful experiments on your own).

Regards,
Dave

 

[dr_dave]

I think you are missing a very important point. The effect is so small that even a tiny piece of dirt or a slight irregularity in the cloth can have a much larger effect. That should give you a better feel for how insignificant "ball turn" truly is. Even a "contrarian" should be able to recognize this (especially if you watch the videos and/or do some careful experiments on your own).

Now, to be clear, ball "turn" is very different from swerve (e.g., due to a non-level-cue, off-center hit on the CB). Swerve (not "turn") is significant and very important. If you don't adjust your aim appropriately for squirt, swerve, and throw, you will miss many shots. There is absolutely no need to adjust one's aim for the insignificant effect of ball "turn."

I hope that clears things up,
Dave

 

[ENGLISH!]

I think you are missing a very important point. The effect is so small that even a tiny piece of dirt or a slight irregularity in the cloth can have a much larger effect. That should give you a better feel for how insignificant "ball turn" truly is. Even a "contrarian" should be able to recognize this (especially if you watch the videos and/or do some careful experiments on your own).

Regards,
Dave

Dave,

I hear you. However, I can not influence the effect of hitting a piece of chalk has, unless... I see it & plan to roll the ball off of one side of it. I can plan & try to influence the cue ball with where & how softly I hit it.

I have been doing 'experiments' through the 46 years I've been playing with english & observing its effects.

It just seems that some aspects seem to be dismissed simply as insignificant or too complicated so why attempt it. (in whose judgment)

I am not of that opinion. I think everything can be significant... & complicated is a relative term.

There is no need to reply Dave. I do not want to de-rail the thread any farther or get into a back & forth that will serve no real purpose. I've had my rant & I should be done.

Thanks again & I appreciate all of your efforts both past & present.

Best Regards,

 

[dr_dave]

There is no need to reply Dave. I do not want to de-rail the thread any farther or get into a back & forth that will serve no real purpose. I've had my rant & I should be done.

I agree completely!

Thanks again & I appreciate all of your efforts both past & present.

You're welcome ... and thank you.

Best regards and Happy Holidays,
Dave