CB transfers no spin to OB - Steve Davis

[Jal]

.... if you hit a cue ball with slow to medium speed and "one tip" of english, the cue ball will lose all or almost all of its english as it rolls the length of the table. try it with a spotted cue ball or a striped ball. the slower the cloth, the quicker it will lose its english.

I'm not sure this is true. A lag shot will reach the first cushion in under two seconds, whereas you can make the cueball spin in place for considerably longer than this?

since the transferred spin to an object ball is much less than "one tip" it will lose its spin very quickly. combine this with the slow nappy cloth used on snooker tables, i can see why some top snooker players doubt it exists.

I agree with this (for what it's worth).

Jim

 

[hanisch]

I dont know why this is so hard to understand. When the balls are very clean, spin induced throw is almost non existent. You might get a half ball's rotation of side before it wears off on the OB. As the balls get dirtier, or when the weather gets more damp, spin induced throw is much more noticeable. It's caused by friction. Dampness and dirt/chalk/etc cause friction.

it depends on what it's dirty with. if it's dirty with grease, from fries say, it might reduce the friction. also, freshly cleaned and waxed balls do have considerable friction. think of the phrase "squeeky clean." and one more thing, even a half rotation of spin can considerably effect the direction a ball comes off a cushion.

william

 

[X Breaker]

I look at this matter in the same way I look at two identical spheres colliding in a linear motion.
1.Is there any linear energy being transferred?
2.If linear energy can be transferred, what is stopping rotational enegry from transferring?
Richard

 

[Colin Colenso]

I look at this matter in the same way I look at two identical spheres colliding in a linear motion.
1.Is there any linear energy being transferred?
2.If linear energy can be transferred, what is stopping rotational enegry from transferring?
Richard

Friction is not required for the tranference of linear momentum, in fact it reduces from such a trasfer, though it is the source of the tranference into angular momentum.

 

[hanisch]

I'm not sure this is true. A lag shot will reach the first cushion in under two seconds, whereas you can make the cueball spin in place for considerably longer than this?
I agree with this (for what it's worth).

Jim

jim,

if you hit the cue ball with one tip of english *at lag speed* into an object ball close by--so that it spins in place--it won't spin for that long. moreover, when a ball is *rolling* along the cloth with some english, it will lose the english more quickly than it would if it were spinning in place. this is due to the rolling ball grabbing the cloth more and thus causing more friction. try it.

william

 

[Jal]

Anyway, interested in how you came up with more spin transference for smaller balls, yet same throw?

It surprised me too. I did go over it a few times to try to make sure (but there's always the possibility I screwed up). A semi-intuitive way of seeing it is that the change in relative surface speed during impact due to the throw and induced spin are at fixed ratios. Namely, for every unit of change due to throw, five times this amount is due to spin (acquired or altered between the two balls). And since the snooker balls are smaller, they have to spin faster to produce the same five times ratio (by the ratio of their radii) If that's not convincing, I'll send you the math details.

That takes care of the spin/throw ratio, but as far as the amount of throw itself being the same, consider that since the object ball takes off at the same speed (our assumption of same initial cueball speed), the compression impulse between the two types of balls must be in the ratio of their different masses. Since the friction impulse is the compression impulse times the coefficient of friction, it is in the same ratio. Throw (the change in linear momentum along the tangent line) is equal to the friction impulse. Dividing both sides by their respective masses yields the same throw speed.

(I worked the math out first because I wouldn't exactly trust this type of reasoning.)

Jim

 

[Jal]

...if you hit the cue ball with one tip of english *at lag speed* into an object ball close by--so that it spins in place--it won't spin for that long.

Yes, of course you're right. Sorry about that - wasn't thinking about the lag shot spin.

moreover, when a ball is *rolling* along the cloth with some english, it will lose the english more quickly than it would if it were spinning in place. this is due to the rolling ball grabbing the cloth more and thus causing more friction. try it.

I'm not saying you're wrong (wouldn't dare at this point!) but this is not obvious to me. As you say, the proof is in the trying, but if you have an expanded argument, I'd be interested in hearing it.

Jim

 

[X Breaker]

Friction is not required for the tranference of linear momentum, in fact it reduces from such a trasfer, though it is the source of the tranference into angular momentum.

I agree friction leads to energy lost in linear motion.

My point, however, is not in stating the difference(s) between the two motions but rather their similiarity, which is the fact that momentum is conserved.

i.e.Initial momentum would equal the final momentum plus energy lost.

Therefore, it is against our basic sciencific principles to state that angular momentum can never be transferred.

Richard

 

[Ronoh]

I dont know why this is so hard to understand. When the balls are very clean, spin induced throw is almost non existent. You might get a half ball's rotation of side before it wears off on the OB. As the balls get dirtier, or when the weather gets more damp, spin induced throw is much more noticeable. It's caused by friction. Dampness and dirt/chalk/etc cause friction.

It takes time for folks to understand that "friction" is the key. I agree with you whole heartly Cuetechasaurus.

 

[pooltchr]

I agree that less spin is transferred using snooker instead of pool balls. The greater mass of pool balls means that the inertial force from spin is greater, and can be transferred easier. A good (and useful) example of the transfer of spin is if you have an ob hanging in a pocket and combo another ob into it, hitting the cb with draw so that the first ob follows the second one in.

If I understand you correctly, you are saying if you shoot the cue with bottom spin on a combo shot, the first ob will pick up top spin so it can follow the second ob into the pocket. If this is correct, then if you put top spin on the cue ball, would that put back spin on the middle ball so it would stop or draw when it hits the last ball?
Steve

 

[hanisch]

Yes, of course you're right. Sorry about that - wasn't thinking about the lag shot spin.

I'm not saying you're wrong (wouldn't dare at this point!) but this is not obvious to me. As you say, the proof is in the trying, but if you have an expanded argument, I'd be interested in hearing it.

Jim

jim,

thanks for replying.

i must, at the current state of my knowledge, ultimately admit ignorance as to what is actually going on with respect to physics. from reading your other posts on this thread, perhaps you can shed some light. (i would be interested in seeing the equations you came up with from your earlier post.) i am mainly going on observations on the table combined with some, albeit weak, heuristic arguments, and could very well be wrong.

first, let's agree that a rolling ball means that it travels one circumference when it rotates along the horizontal axis (i.e. forward spin) once. if it travels more than one circumference when it rotates once, then it's "under spinning." if it travels less, it's "over spinning." when it's rolling, as opposed to under or over spinning, it's grabing the cloth more, i think. this is admitedly vague; perhaps you can state it more precisely. it's this grabbing that, if true, is causing any side spin to dissipate more quickly. there are other effects of a rolling ball that go unnoticed by many players (i think), which may add some insights to this.

for instance when a cue ball is rolling when it hits an object ball with, say, a half ball hit, it will follow earlier than if it's over spinning. that is, an over spinning ball will travel along the tangent line (or close to it) longer than a rolling ball, before it follows forward. most people, i believe, think that it's speed alone that determines this, but i think whether it's rolling or over spinning has more to do with it. note that a ball can be either rolling or over spinning at many different speeds. it starts to move forward when the speed and forward spin match, so to speak. when it "fully grabs," it's matched.

i hope you can add some further insight and analysis to this, whether i'm right or wrong.

william

 

[mikepage]

If I understand you correctly, you are saying if you shoot the cue with bottom spin on a combo shot, the first ob will pick up top spin so it can follow the second ob into the pocket. If this is correct, then if you put top spin on the cue ball, would that put back spin on the middle ball so it would stop or draw when it hits the last ball?
Steve

I think the initial premise is wrong. The first object ball follows the second in when it has picked up top spin due to friction with the cloth, not from transferred spin from the cueball. So the first object ball will follow the second the most when it has achieved natural roll. You can do this with draw or stun or follow on the cueball. However, if you hit the first ball hard or it is close to the second object ball, then it will still be sliding when it hits the second object ball and it will not follow.

I have tried experiments with the two object balls close and with a nearly full hit with maximum follow to see whether I could see the transferred spin effect you talking about. I could never get the first object ball to come backwards of the tangent line.

mike page
fargo

 

[mikepage]

throw and imparted spin are two separate phenomena, both of which are effects of the same causes. one cause is cutting a ball. the friction of a cue ball cutting across the face of an object ball causes the object ball both to throw slightly in the direction of the cue ball's initial path (i.e. the cue ball grabs the object ball and takes the object ball with it for a little bit) and to spin with the english of the side that the object ball was hit (i.e. if the object ball was hit on its left side, it will get left english) from brushing across it.

the other cause is putting english on the cue ball, while hitting the object ball fairly full. the effect of the friction caused by the english both throws the object ball off line (to the opposite direction of the english) as well as transfers (opposite) spin to the object ball (like gears). (note that the object ball does not throw because it has english. rather it both throws and spins from the friction.) again, this throw and imparted spin are two separate phenomena, both having two distinct causes from friction, viz. a cutting cue ball or a spinning cue ball.

[...]

I view both causes you mention as really being the same. That is, there is friction from the two ball surfaces rubbing against one another. The object ball doesn't understand whether the cueball is rubbing against it because of an angle or because it is spinning or some combination.

I note also that words like "grab" and "gears" are misleading for this interaction and they lead people astray, imo. This is not static friction. The two surfaces are never locked together. If they were, you would expect more throw at higher speeds, and that's not what we see.

mike page
fargo

 

[Colin Colenso]

jim,

thanks for replying.

i must, at the current state of my knowledge, ultimately admit ignorance as to what is actually going on with respect to physics. from reading your other posts on this thread, perhaps you can shed some light. (i would be interested in seeing the equations you came up with from your earlier post.) i am mainly going on observations on the table combined with some, albeit weak, heuristic arguments, and could very well be wrong.

first, let's agree that a rolling ball means that it travels one circumference when it rotates along the horizontal axis (i.e. forward spin) once. if it travels more than one circumference when it rotates once, then it's "under spinning." if it travels less, it's "over spinning." when it's rolling, as opposed to under or over spinning, it's grabing the cloth more, i think. this is admitedly vague; perhaps you can state it more precisely. it's this grabbing that, if true, is causing any side spin to dissipate more quickly. there are other effects of a rolling ball that go unnoticed by many players (i think), which may add some insights to this.

for instance when a cue ball is rolling when it hits an object ball with, say, a half ball hit, it will follow earlier than if it's over spinning. that is, an over spinning ball will travel along the tangent line (or close to it) longer than a rolling ball, before it follows forward. most people, i believe, think that it's speed alone that determines this, but i think whether it's rolling or over spinning has more to do with it. note that a ball can be either rolling or over spinning at many different speeds. it starts to move forward when the speed and forward spin match, so to speak. when it "fully grabs," it's matched.

i hope you can add some further insight and analysis to this, whether i'm right or wrong.

william

William,
The CB after it leaves the cue rarely overspins for any noticeable length. In fact, it is hard to find any real play shot where it occurs, unless you are powering topspin from a few inches away from the OB.

Top spin shots are basically rolling for all practical purposes.

 

[mikepage]

William,
The CB after it leaves the cue rarely overspins for any noticeable length. In fact, it is hard to find any real play shot where it occurs, unless you are powering topspin from a few inches away from the OB.

Top spin shots are basically rolling for all practical purposes.

I agree with this. But as soon as that rolling cueball strikes an object ball, it suddenly has overspin.

mikepage
fargo

 

[Island Drive]

Transfer

If the spin rotation of the cue ball is the same then the following principles apply. When the cue ball collides with the object ball, more is transferred at lower speeds, more is transferred when the balls are not clean, more is transferred when conditions are wet and too on another note: more spin can be created/therefore transferred when you hit the cue ball along the horizontal plane (9 and 3 o'clock). A simple example of spin transfer is when you hit a cue ball extreme low 6 o'clock and lets say the cue ball is moving at .4 mph notice that the object ball moves faster lets say .5

 

[pete lafond]

I think the initial premise is wrong. The first object ball follows the second in when it has picked up top spin due to friction with the cloth, not from transferred spin from the cueball. So the first object ball will follow the second the most when it has achieved natural roll. You can do this with draw or stun or follow on the cueball. However, if you hit the first ball hard or it is close to the second object ball, then it will still be sliding when it hits the second object ball and it will not follow.

I have tried experiments with the two object balls close and with a nearly full hit with maximum follow to see whether I could see the transferred spin effect you talking about. I could never get the first object ball to come backwards of the tangent line.

mike page
fargo

Transfer of spin is negligible. There is a spin transfer that occurs except it is not noticeable because it is so instantaneous that the friction from the cloth very quickly negates it. Additionally the balls are so smooth that not enough friction between the ball exists and is minimized at impact.

The felt is the largest factor in preventing over spin and under spin from becoming a factor in transfer. (this should not be confused in the case of placing overspin on the CB that will cause it to rise above the felt surface and then drop on the OB causing slight reverse)

Side spin works on different principles. 1. Inside English for example works against the natural transfer of spin. (think of the same cut and notice contact induced spin on the CB - this is the same effect of putting a draw on the CB which causes the CB to spin backwards while it continues moving forward on its way to the OB). The energy of the CB spinning sideways is so great that friction is minimized. 2. Outside English works as a more natural flow and is noticed by throw.

Notes: The moment of contact is so short that any transfer is near impossible which is why two balls touching exhibit greater effects with English than those not touching.

 

[Colin Colenso]

I view both causes you mention as really being the same. That is, there is friction from the two ball surfaces rubbing against one another. The object ball doesn't understand whether the cueball is rubbing against it because of an angle or because it is spinning or some combination.

I note also that words like "grab" and "gears" are misleading for this interaction and they lead people astray, imo. This is not static friction. The two surfaces are never locked together. If they were, you would expect more throw at higher speeds, and that's not what we see.

mike page
fargo

Mike,
I have played the shot with draw which causes the first ball to follow through quite a lot. It requires near perfect accuracy but certainly the tranfered topspin is noticeable.

For the topspin shot. I haven't see an OB come back from the tangent line, but I will use topspin on a plant where I want the OB to travel as much as possible on the tangent line and I don't have the positional options to play it as a fine cut.

Colin

 

[mikepage]

Mike,
I have played the shot with draw which causes the first ball to follow through quite a lot. It requires near perfect accuracy but certainly the tranfered topspin is noticeable.

For the topspin shot. I haven't see an OB come back from the tangent line, [...]

Colin

I can think of two other causes (besides transferred spin) of the middle ball going forward. First is, as I said, topspin on the middle ball from friction with the cloth. Second is any inelasticity of collision between the two object balls would cause the middle ball to go forward.

I'm sceptical. I would think if it works to any practical degree for the backspin shot (to put follow on the middle ball), it should also work with the topspin shot (to put backspin on the middle ball). I haven't seen anthing that convinces me.

mike page
fargo

 

[mikepage]

[...]if you hit a cue ball with slow to medium speed and "one tip" of english, the cue ball will lose all or almost all of its english as it rolls the length of the table. try it with a spotted cue ball or a striped ball. the slower the cloth, the quicker it will lose its english. since the transferred spin to an object ball is much less than "one tip" it will lose its spin very quickly. combine this with the slow nappy cloth used on snooker tables, i can see why some top snooker players doubt it exists.

finally, the effect of transferred spin is most pronounced when the object ball is close, or frozen, to a cushion. this is because the object ball doesn't have time to lose its spin before it hits the cushion and rubs off it.

william

I think there are *three,* (not two) relevant numbers that characterize cloth. First is the table speed, which has to do the rolling resistance and can be thought of as a pseudo frictional force. (Is the cloth fast?)

The second is the ball-cloth friction, i.e. (Is the cloth slick?)

These are the two people talk about. The third has to do with how fast sidespin is wiped off. I think this one may be related to the other two, but I don't think it's a simple consequence of either one.

mike page
fargo