Slide or Roll?

[gwvavases]

I just returned to the game a few years ago after a 26-yr absence from playing. I've never really thought about it before, but I began wondering a while ago (after spending a few hours playing pool with AZB-fav Purdman, and meeting a few other local AZBers) whether cue balls slide or roll when they're hit with sidespin.

A ball can only TURN one direction, can't it?

The earth couldn't spin pole-to-pole while spinning on it's axis, can it?

So...seems to me that if any hit OTHER than high-center is made (and even a little then, too), the cue ball will be sliding while spinning as it makes it's way to the object ball...like a ballerina pirouetting as she drifts across a stage!


Am I right? (Or did Purdman whack my brain a little?)

George in Alex., VA

 

[RiverCity]

The ball is sliding while spinning, no matter what spin you put on it. The only time it isnt sliding..... is when its rolling naturally as in a soft follow shot, or a shot where the spin has already been rubbed off the ball by the friction of the cloth.
To illustrate the point a little more, think of an extreme follow, draw or masse shot. You have put so much spin on the ball in those examples, that the sliding action while spinning is a little more obvious. But the same thing is happening on a softer shot where you have put more spin on the ball than would be there normally with a naturally rolling ball.
Chuck

 

[desert1pocket]

The ball is sliding while spinning, no matter what spin you put on it. The only time it isnt sliding..... is when its rolling naturally as in a soft follow shot, or a shot where the spin has already been rubbed off the ball by the friction of the cloth.
To illustrate the point a little more, think of an extreme follow, draw or masse shot. You have put so much spin on the ball in those examples, that the sliding action while spinning is a little more obvious. But the same thing is happening on a softer shot where you have put more spin on the ball than would be there normally with a naturally rolling ball.
Chuck

Well said. I saw some slow motion videos somewhere and was surprised at how often the balls aren't even touching the table. On even med hard shots, the balls are actually skipping across the table for quite a while.

 

[zhouray]

So...seems to me that if any hit OTHER than high-center is made (and even a little then, too), the cue ball will be sliding while spinning as it makes it's way to the object ball...like a ballerina pirouetting as she drifts across a stage!

From what I know, friction between the cloth and the ball would cause the ball to accumulate forward spin. i.e. Even if you hit the cue ball at the center or bottom, it will eventually be rolling forward due to the friction.

 

[gwvavases]

Exactly! Except...

The ball is sliding while spinning, no matter what spin you put on it. The only time it isnt sliding..... is when its rolling naturally as in a soft follow shot, or a shot where the spin has already been rubbed off the ball by the friction of the cloth.
To illustrate the point a little more, think of an extreme follow, draw or masse shot. You have put so much spin on the ball in those examples, that the sliding action while spinning is a little more obvious. But the same thing is happening on a softer shot where you have put more spin on the ball than would be there normally with a naturally rolling ball.
Chuck

I agree...almost entirely. There don't seem to be too many shots in which a forward moving cue ball is actually rolling (only soft follow shots as you mentioned). I'm not so sure I agree with you that a shot with extreme (centerball) follow is actually sliding, though. Anybody know for sure? Seems to me that extreme follow doesn't actually cause a cue ball to spin faster than it is actually moving forward across a table (i.e. like popping the clutch and laying rubber with a car), but that it is the kinetic energy imparted on the ball by the hard, high centerball hit that causes it to follow so strongly.

Agree?

George in Alex., VA

 

[RiverCity]

I agree...almost entirely. There don't seem to be too many shots in which a forward moving cue ball is actually rolling (only soft follow shots as you mentioned). I'm not so sure I agree with you that a shot with extreme (centerball) follow is actually sliding, though. Anybody know for sure? Seems to me that extreme follow doesn't actually cause a cue ball to spin faster than it is actually moving forward across a table (i.e. like popping the clutch and laying rubber with a car), but that it is the kinetic energy imparted on the ball by the hard, high centerball hit that causes it to follow so strongly.

Agree?

George in Alex., VA

In the situation you mention, sliding may not be the correct action..... skipping may more proper. You can put more forward spin on the cueball than the converse of the ball rolling at the same speed as the topspin.
When I was learning position play, I used a stripe ball as the cueball so that I could see the ball spinning. Take a stripe, put it on the spot and turn it so that the strip is horizontal. Now shoot it straight down the table at the middle diamond on the end rail. Hit it at the top of the stripe so that the edge of your tip just hits the top of the stripe (pretty much as far off center as you can go while still getting usable spin). And again, you can see the excess spin involved. Another view of the "skipping" action on a centerball extreme follow is after full hit collision with another ball, sometimes you'll see a pause with the cueball spinning before it grabs and goes forward. The cueball is skimming the surface of the cloth, while it has faster spin than the speed of the forward movement.
Chuck

 

[mbvl]

The ball is sliding while spinning, no matter what spin you put on it. The only time it isnt sliding..... is when its rolling naturally as in a soft follow shot, or a shot where the spin has already been rubbed off the ball by the friction of the cloth.
To illustrate the point a little more, think of an extreme follow, draw or masse shot. You have put so much spin on the ball in those examples, that the sliding action while spinning is a little more obvious. But the same thing is happening on a softer shot where you have put more spin on the ball than would be there normally with a naturally rolling ball.
Chuck

It's a bit more complicated than that. The ball is rolling without sliding most of the time even when it's spinning.

Suppose you wanted to move a heavy barrel. You would tip it up so only one point was touching the floor with the center of gravity above the point of contact. Then you would "roll" the barrel so that it moved in a straight line keeping the center of gravity above the contact point. Thus the barrel would move in a straight line while "rolling" along the floor, but it would also be "spinning". Now imagine the barrel embedded in a sphere. The sphere is spinning while rolling without slipping. This is how a billiard ball moves most of the time.

Mark

 

[Fatboy]

the cloth also is a consideration, on super fast cloth simonis 300(?) the billiard cloth, the ball is almost awalys sliding, on slow cloth in a humid enviroment where there is more friction the ball will roll more because there is alot more friction and the cue ball bites faster, also after a ball hits a rail it rolls more than right when you hit it, with the cue on a kick shot for example, after about 3 rails if the cue ball hasnt hit any other balls its pretty much rolling thus changing the angle after it comes off the rail.