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DoomCue
03-30-2004, 12:26 PM
I guess this question is more for the physics-minded players out there. I was taught that maximum spin on the CB is achieved by accelerating through the CB. Is this true? Does acceleration, lack of it, or deceleration have an effect on spin? Isn't velocity far more important than acceleration as far as spin is concerned?

I would assume that the ideal contact would be done at zero acceleration, but is this physically possible to consistently reproduce? For instance, in a thread on RSB, it was postulated that when the forearm is perpendicular to the floor during the pendulum stroke, acceleration is zero. I'm not too sure that's true. If it is true, then I guess it's relatively easy to reproduce; just make sure contact is made when the arm is perpendicular to the floor. If it isn't true, then how does a human determine when acceleration is zero, increasing, or decreasing?

I'm not sure if knowing these things will help my game, but I'm curious....

-djb

Fred Agnir
03-30-2004, 12:45 PM
<blockquote><font class="small">Quote DoomCue:</font><hr> I guess this question is more for the physics-minded players out there. I was taught that maximum spin on the CB is achieved by accelerating through the CB. Is this true? <hr /></blockquote>
I say it isn't true.

[ QUOTE ]
Does acceleration, lack of it, or deceleration have an effect on spin?<hr /></blockquote>

I say , "no."

[ QUOTE ]
Isn't velocity far more important than acceleration as far as spin is concerned?<hr /></blockquote> I say this is absolutely true.

[ QUOTE ]
I would assume that the ideal contact would be done at zero acceleration, but is this physically possible to consistently reproduce? <hr /></blockquote>

Zero or near zero would be more repeatable, IMO.

[ QUOTE ]
For instance, in a thread on RSB, it was postulated that when the forearm is perpendicular to the floor during the pendulum stroke, acceleration is zero. I'm not too sure that's true.<hr /></blockquote>

I would say this is true. When the arm is approaching perpendicular, the cue's acceleration in the forward direction is decreasing to the point of zero acceleration (constant velocity). I think for the most part, most non-physics people just have the terminology wrong.

[ QUOTE ]
If it is true, then I guess it's relatively easy to reproduce; just make sure contact is made when the arm is perpendicular to the floor. <hr /></blockquote> I think empirically, that's what most instructors have learned to teach. Slight differences in arm position at contact is most forgiving around perpendicular from a speed control perspective.

Fred

BeanDiesel
03-30-2004, 03:13 PM
<blockquote><font class="small">Quote DoomCue:</font><hr> Does acceleration, lack of it, or deceleration have an effect on spin? <hr /></blockquote>

I agree with Fred. However you accelerate the cue, the quantity that affects the angular velocity (spin) is the velocity of the cue at the moment of impact.

<blockquote><font class="small">Quote DoomCue:</font><hr>
Isn't velocity far more important than acceleration as far as spin is concerned?
<hr /></blockquote>

Honestly, i dont really understand this question, and Fred, can u please explain your response to this question.

Fred Agnir
03-30-2004, 03:49 PM
<blockquote><font class="small">Quote BeanDiesel:</font><hr> <blockquote><font class="small">Quote DoomCue:</font><hr> Does acceleration, lack of it, or deceleration have an effect on spin? <hr /></blockquote>

I agree with Fred. However you accelerate the cue, the quantity that affects the angular velocity (spin) is the velocity of the cue at the moment of impact.

<blockquote><font class="small">Quote DoomCue:</font><hr>
Isn't velocity far more important than acceleration as far as spin is concerned?
<hr /></blockquote>

Honestly, i dont really understand this question, and Fred, can u please explain your response to this question.
<hr /></blockquote>I think you answered it yourself when you said:

"the quantity that affects the angular velocity (spin) is the velocity of the cue at the moment of impact. "

Fred

tateuts
03-30-2004, 06:36 PM
This would be my response. I don't think it matters if the cue actually is accelerating or not. I think it helps us to "feel" like it is (smoothly) accelerating.

Second, I want to do things to keep the cue moving and not to unintentionally slow it down. I think the real danger is in decelerating the cue with a jerky stroke, By thinking "smooth acceleration" I will increase my chance of making a better stroke.

Chris

1Time
04-02-2004, 08:35 AM
The rate at which accelerating through the cue should increase depends on the shot being taken and what you are attempting to do with the shot. The speed of the stroke at contact of course also varies.

If the rate of acceleration was charted on a graph where time was the horizontal axis and speed was the vertical axis, for some shots the line should be shorter and slope only slightly upward. For others the line should be longer and the slope of the curve should be more dramatic. Generally, faster strokes would graph as shorter lines and slower strokes would have the potential for being graphed as longer lines. The longest line that could be graphed would be a stroke that begins at a relatively slow speed up to the point of contact with the cue ball and then gradually but then later dramatically increases in acceleration through the cue ball. Just imagine how this could result in keeping your cue tip in contact with the cue ball for as long as possible through the stroke. Of course this should not and need not be the objective. However, having some understanding of what I've described can aid in learning to appropriately vary the acceleration of one's stroke through the ball.

On a few occasions I've had lesser competitors complain as I ran the rack on them that some of my shots appeared to be illegal since it looked like I was literally "pushing" the ball with my cue tip. In order to obviate further contention I would explain that as long as the cue tip remains in contact with the cue ball during the stroke that it was legal, and then I would offer to demonstrate and explain if they wanted. For the few who asked, I began by explaining that the cue tip remains in contact with the cue during a brief part of everyone's stroke and for every shot, but that it remains in contact for different lengths of time for different strokes. It's just that when the cue tip remains in contact a little longer than other shots, it can have the illusion of literally pushing the cue ball.

I first learned the difference between "stroking" and "poking" the shot over 20 years ago. However, it wasn't until years later that I saw for myself the definition of "stroking" personified, when I first saw Keith McCready play in person. It was like nothing I had seen before. I just had to learn to stroke the ball like he did and I practiced until, to a lesser degree of course, I could. The beauty of watching him stroke the ball reminded me of when I first saw Tony Gwynn in person handle the bat at the plate... absolutely amazing.

Steve - Detroit
04-02-2004, 12:53 PM
<blockquote><font class="small">Quote 1Time:</font><hr>

If the rate of acceleration was charted on a graph where time was the horizontal axis and speed was the vertical axis, for some shots the line should be shorter and slope only slightly upward. For others the line should be longer and the slope of the curve should be more dramatic. Generally, faster strokes would graph as shorter lines and slower strokes would have the potential for being graphed as longer lines. The longest line that could be graphed would be a stroke that begins at a relatively slow speed up to the point of contact with the cue ball and then gradually but then later dramatically increases in acceleration through the cue ball. <hr /></blockquote>

Why do you assume the graph would be a line? It would seem to me that it would be an arc with contact at a point where the graph was leveling out at the desired velocity for the shot at hand.

1Time
04-02-2004, 01:31 PM
Good point and thank you Steve - Detroit. I probably used the wrong term when I said "line". Yes, it would be more of an "arc". I just imagined a bending line while I was writing. It would only be a straight line if the velocity was constant. And then, as the speed of the cue tip increased through the cue ball, the "arc" in the graph would bend even more on that end.

One other thing I may not have made clear is the graph I described is of the time the cue tip touches the cue ball to when it is no longer in contact with it.

Bob_Jewett
04-09-2004, 01:08 PM
<blockquote><font class="small">Quote DoomCue:</font><hr>Isn't velocity far more important than acceleration as far as spin is concerned?

I would assume that the ideal contact would be done at zero acceleration, but is this physically possible to consistently reproduce?
<hr /></blockquote>

If you can get a copy of the November 1998 Billiards Digest, an article explains exactly why you want to hit the cue ball at zero acceleration. It is the most efficient and most consistent way to hit the ball. People who advocate something else often have no real understanding of the terms.

For some students, it may help them to be told to accelerate through the ball just to keep them from stopping too early in their stroke.

I think that good players naturally hit the ball at peak stick speed just through trial and error.