The Myth of Top Spin???

av84fun said:
on a freight train going east at 60MPH, there is always a part of the train that is moving west.

The wheels as they rotate counter-clockwise past 9 o'clock???????????

(-:
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I don't think there is any part of the train that is moving in the opposite direction it is travelling. The closest anypart of the wheel would be to moving backwards is when a point on the wheel is at 6 oclock. Then it stops moving down towards the ground and moves up and forward away from it.

My physics teacher explained this quite thouroughly, not convincing half the class. His example was as you are driving behind a car and it throws a rock toward your car, that rock is actully moving away from you and you drive into it. It cannot be thrown backwards because in relation to the ground there is NO part of the wheel that moves opposite of the direction of the wheel.

He had a wheel with a dot on it. We were asked to watch that dot and say when it moved backwards in realtion to the ground. It doesn't.

Alot to say about nothing.

I am curiouse what the original poster has to say about the train moving backwards?
 
av84fun said:
Thanks but you didn't answer my question...

Originally Posted by av84fun
And there is no applied force causing friction between the spinning cb and the cloth unless there was first forward (linear) momentum....RIGHT?

Do you agree that the cb could not be "rotating on its axis in a forward direction" had it not been caused to move and roll forward in the first place?

And would it be therefore correct to state that the force that INITIATED the whole process was a cue stick striking a CB such that forward and rolling momentum was imparted?

I think that would be true unless there is such a thing as "immaculate angular momentum."

(-:

Regards,
Jim
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I think maybe we are talking about two different things. I agree that the strike of the cue stick started the forward motion of the cb and the rotation of the cb at the same time,however the two motions are completly independant and separate of each other. I was replying to the statement made that the cb stops when it strikes the ob and then starts forward again because of it's original forward momentum. This is not possible.
 
Um....guys....this is BASIC physics here.

Theoretically, it is possible to get topspin (i.e. cueball spinning faster than natural roll), but there is only one condition that this could possibly happen. THE COEFFICIENT OF FRICTION OF THE CUE-TIP ON THE CUE BALL MUST BE GREATER THAN THE COEFFICIENT OF FRICTION OF THE CLOTH ON THE CUEBALL.

Given currently available technology on cue tips, we cannot yet achieve topspin per the above definition. The cue tips simply do not exert enough friction to do this.


The reason why backspin (or draw shots) work is because hitting below center-ball actually reduces the cloth/cueball friction because you are "lifting" some of the weight of the cueball off the cloth. Therefore, under such conditions, the coefficient of friction of the cue-tip/cueball outweighs that of the cloth/cueball and backspin is achieved.

Also note that the coefficient of friction is dependant on the angle of attack.... center ball hit = maximum coeffient....and you can send the cueball floating across the table with literally no spin if hit hard enough. Even a gentle centerball hit causes the cueball to float, but for just a very short distance.

Donald
 
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3andstop said:
I'd like a stab at adding to the confusion with my interpretation of what happens. :)

I don't know if there really is or not, but we can think of a CB hit with above center english as having "2" completely seperate forces applied to it.

1. the forward momentum.

2. the circular momentum, whether it equals the forward roll on a 1 to 1 ratio or not.

The second force is an additional force to that of a CB hit with center english. Even if hit very hard, a center ball hit on the CB sends it on its way with forward ("1") momentum but with no ("2") circular momentum. It is merely sliding down the table.

When a center ball hit CB hits an OB fully the equal masses cause a transfer of energy and the OB takes off while the CB stops.

Not so with a CB hit with follow english. This cue ball is not sliding. It is rolling, even if only on a 1 to 1 ratio with its forward movement. It is still a rolling mass, not a sliding mass. The harder you hit it, the faster the circular momentum, still even if only on a 1 to 1 ratio with its forward movement.

When it hits the OB result number 1 still happens and it transfers energy, and stops, but because the circular energy exists now in addition to the forward energy, the CB now resumes forward movement.

The visual of the OB overspinning as it resumes its forward movement is a result of the removal of most or all of the number ("1") momentum by the contact to the OB.

All that is left to be seen with the eye, is the practically full amount of the number ("2") momentum.

Look at it this way. When you force draw a CB, think of how hard you hit it and how hard it reverses direction. The speed of its reverse direction can be compared to the speed of a "rolling forward" CB that was hit with follow.

The forward circular spin doesn't have to be greater that a 1 to 1 ratio in order for the effect to occur, it just has to exist.
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Excellent post Sir, I believe this covers the topic very well.
 
Curt said:
Im refering to the article by Tom Simpson in the May/June Indide Pool Mag, page 26. Has anyone else who's read this article come away with disbelief as I did? Mr Simpson says top spin doesn't exist, that overspin means the cue ball would be spinning faster than it is rolling and THAT DOESN"T HAPPEN! Does anyone believe as I do that Mr simpson needs to make a distinction between natural follow and force follow, where "over spin" does indeed occur. I belive these written remarks coming from a "BCA Master Instuctor" are misleading and ambiguous. Comments anyone?
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I didn't read the article, but agree with him based on your explanation of his article.

Think of the CB's rotation in relation to the cue tip's velocity upon impact. For overspin to occur, the CB RPM will have to exceed the tip's velocity. To me, this violates Newton's laws of motion.
 
nativeMT said:
For overspin to occur, the CB RPM will have to exceed the tip's velocity. To me, this violates Newton's laws of motion.
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Not true. Imagine a cueball with a small metal plate protruding out. Position the cueball with the metal plate pointing upwards and with your cue, strike that metal plate as hard as you can. You will find that there is indeed "overspin", as the metal plate will slam into the cloth well before the cueball starts to move.

This metal plate simulates maximum coefficient of friction. See my earlier post for more details.

Donald
 
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Top Spin

If top spin is removed with in inches of travel then explain a break shot that is hit with max follow and hit the apex ball full in the face and back up 8 to 10 inches then over spin takes over and runs back into the rack.
 
Neil said:
I guess I will add my 2 cents to this also. I say you CAN get overspin on the cb. If you hit below center- draw, you obviously have overspin on the cb. If you didn't, it would never come back towards you. Granted, the cb will be airborne for a very short distance, and then have a few very small hops before it is rolling down the table with backspin still on it. It is not airborne for a table length draw shot.

Yet, some say that if you hit the same, but opposite place on the cb, you do not get overspin. Or if you do, it is only for a few inches, because the friction of the cloth will dissipate it almost immediately.

You can't have it both ways. Either you can get overspin, or you can't draw.
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Follow spin is in the same direction as if the CB is rolling. Draw spin is in the opposite direction.

Haven't you ever seen the cueball start foward, and actually pick up speed the farther it goes?
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It does for a few inches (with overspin), but you can't see it.

To all those that say you can't get force follow- you have one less shot in your arsenal.
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Force follow is just hard follow. It isn't necessarily overspin.

If the cb only ever has a 1:1 rolling ratio, it will go forward or backwards at the same speed every single time. It cannot do otherwise.
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1:1 rolling ratio just means the ball is rolling without "peeling out" or "skidding". For instance, a car's tires normally roll at a 1:1 ratio, but cars go at many different speeds.

pj
chgo
 
nativeMT said:
I didn't read the article, but agree with him based on your explanation of his article.

Think of the CB's rotation in relation to the cue tip's velocity upon impact. For overspin to occur, the CB RPM will have to exceed the tip's velocity. To me, this violates Newton's laws of motion.
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Correct, neither the forward speed of the cb nor the rotation can exceed or equal the speed of the cue stick. The direction of the rotation is the deciding factor for the application of "english". You cannot over spin the cb and increase it's forward speed.
 
MT Pockets said:
If top spin is removed with in inches of travel then explain a break shot that is hit with max follow and hit the apex ball full in the face and back up 8 to 10 inches then over spin takes over and runs back into the rack.
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Top spin is not removed within inches. Overspin ("peeling out") is.

pj
chgo
 
MT Pockets said:
If top spin is removed with in inches of travel then explain a break shot that is hit with max follow and hit the apex ball full in the face and back up 8 to 10 inches then over spin takes over and runs back into the rack.
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If the cue ball backs up 8 to 10 inches after striking the apex of the rack, then one of two things must be occuring:

1) the rack was not racked tight enough
2) the cue ball is lighter than the other balls.

Donald
 
nativeMT said:
For overspin to occur, the CB RPM will have to exceed the tip's velocity.
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Not true. If you hit high enough the CB's spin is (momentarily) faster than its speed. That's all that's necessary. The tip's velocity is irrelevant.

pj
chgo
 
Great post and discussion. Funny timing wise, this was the exact topic of my "philosophical discussion" I had at the recent pool school with another student, and I hadn't seen the topic or discussed it in years. We were doing an exercise that required hitting an object ball fairly thin down the rail and using follow to get to a specific spot on the rail, and he asked what type of follow stroke to use. I knew what he was getting at, but he made a statement that I had to disagree with, hence the "discussion". It was this same statement, that hitting the ball higher then that 70% mark or so does not increase the amount of follow, that you can't create more than a very minimal amount of overspin on the cue ball (ball spinning forward faster than it is rolling), and that force follow is a result of contacting another ball and is a result of speed, not how high the cue ball was originally struck. Actually Tony Robles was interested because he wasn't aware I don't think of some of the physics behind this, as I wasn't until reading articles by the experts.

Now that I've read these posts, I remember where I read some of this information, the excerpt from Byrne's book, the Science of Pocket Billiards, and probably other articles over the years as well. As another poster stated, I stopped trying to hit the ball as high (in the miscue area) to get extreme follow after reading these articles, and became a little more consistent with my follow shots. I used to play a lot of 3 cushion billiards where force and stroke shots are used more practically then they are for pool. Trust me, if I'm hitting a standard force follow off the rail shot to a ball that's across the table from me, for instance to get it to double the rail for a point, I don't need to hit as high as possible, the more pure hit I get on the cue ball and the more speed I use, the more force follow effect I get AFTER hitting the object ball. I was never great at physics, so I don't remember the technical explanations about momentum and such, but it all made sense when I read it. I believe Byrne or someone else said that you can hit the cue ball high to get the cue ball rolling more quickly than natural roll, but given enough distance you can hit the ball very slightly above center and firmly and when it hits the object ball the effect would be the same as from a short distance with maximum follow.

Of course masse-type strokes are exempted from this rule, and the original point I think Simpson was trying to make. And draw and sidespin are different because the spin is in a different direction than the roll of the ball, so some of the similarities that people have tried to make between that and topspin can not be used.

Again, great discussion!
Scott
 
Neil said:
EDIT: I just read the post right above mine. It sounds good at first. But, I believe it is partially flawed. If the cb only ever has a 1:1 rolling ratio, it will go forward or backwards at the same speed every single time. It cannot do otherwise.
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Yes it can only go the same speed every time. The same speed, that is "relative" to the speed it was hit initially.

And, it will go the same distance every time, as its only momentum is from the friction of a 1:1 spin starting from a dead forward momentum action. So, to go different distances, it has to have been spinning more than a 1:1 ratio.
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Not more than 1 to 1 necesarilly, but more times. Still perhaps 1 to 1 but much faster, as in hit harder with more speed and velocity.

A CB rolling at 1mph rolls with the same ratio as one rolling at 20mph, but they will go different distances after contacting an OB or rail given identical circumstances.

The relationship of the forward movement of the CB to its own circular rolling movement, in terms of ratios to each other as it moves down the table, are nowhere near as relevant or crucial to the results we are talking about as is the speed of the rolling and the energy it has.
 
8-Baller said:
If the cue ball backs up 8 to 10 inches after striking the apex of the rack, then one of two things must be occuring:

1) the rack was not racked tight enough
2) the cue ball is lighter than the other balls.

Donald
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An equal-weight cue ball bounces back from a rack because it's running into a greater mass than itself (more than one ball).

A lighter cue ball (#2) also does it, but a loose rack (#1) has the opposite effect.

pj
chgo
 
Patrick Johnson said:
Not true. If you hit high enough the CB's spin is (momentarily) faster than its speed. That's all that's necessary. The tip's velocity is irrelevant.

pj
chgo
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Don't mean to argue, but the speed of the surface of the cb can never be greater than the speed of the cue tip. Not sure what people are refering to as "over spin". Would that be any thing like being to throw a ball faster than your hand can move?
 
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