If the tip and cue ball only touch so briefly, why the difference in power?

[arsenius]

I think many people on this board are familiar with those high speed films of the cue hitting the cue ball. I think it was Bill Porter who said that no matter what they did during those tests they could not increase the contact time between the tip and the ball.

If that is the case, where does the extra power in a stroke come from? I think most people would agree that it doesn't come from hitting the ball harder. For myself, I know that I get the most stroke on a ball when I'm hitting quite softly. It feels like I'm just moving my hand to my shoulder, no more effort than that.

So, if you can't increase contact time, and hitting harder doesn't seem to help, where the HECK does stroke come from, with regards to physics?

 

[Solartje]

I think many people on this board are familiar with those high speed films of the cue hitting the cue ball. I think it was Bill Porter who said that no matter what they did during those tests they could not increase the contact time between the tip and the ball.

If that is the case, where does the extra power in a stroke come from? I think most people would agree that it doesn't come from hitting the ball harder. For myself, I know that I get the most stroke on a ball when I'm hitting quite softly. It feels like I'm just moving my hand to my shoulder, no more effort than that.

So, if you can't increase contact time, and hitting harder doesn't seem to help, where the HECK does stroke come from, with regards to physics?

contact friction between the tip and the cb i guess. The more friction the better the stroke
the friction is dependant of:
- amount of englisch used
- type of shaft used
- type of tip used
- how clean the cb is
- amount of chalk used
- type of chalk used
- but mainly i think: the speed and aceleration ratio from the cuetip vs the cb. cb starts at 0mph and goes to X mph, with acceleration Y, where as the cue starts at 0mph and goes to X mph , with acceleration Z dependant of the lenght between where the tip is at the pause of the backswing and the place where the tip hits the cb.

i think the stroke power is a factor of Y/Z.

the higher the acceleration difference is, the more powerfull stroke you will get i think.


ow wait.... in fact, i have NO idea at all

 

[mikepage]

I think many people on this board are familiar with those high speed films of the cue hitting the cue ball. I think it was Bill Porter who said that no matter what they did during those tests they could not increase the contact time between the tip and the ball.

To further put you in a tizzy, the contact time is actually a bit shorter on a hard shot.

If that is the case, where does the extra power in a stroke come from? I think most people would agree that it doesn't come from hitting the ball harder.

I'n not sure what you mean. The stick goes faster into the ball. The force is bigger with a faster stick.

For myself, I know that I get the most stroke on a ball when I'm hitting quite softly. It feels like I'm just moving my hand to my shoulder, no more effort than that.

I'm afraid I don't know what you mean.

So, if you can't increase contact time, and hitting harder doesn't seem to help, where the HECK does stroke come from, with regards to physics?

Again, I'm not sure I really understand the question.

 

[Patrick Johnson]

where does the extra power in a stroke come from?

What "extra" power?

I think most people would agree that it doesn't come from hitting the ball harder.

I don't think most people would know what you mean. If you mean why does hitting the cue ball at the same speed sometimes give the CB more speed, I don't think that's true. If you want the CB to go faster, you have to hit it with more speed (harder).

There's no voodoo in pool.

pj
chgo

 

[sygfrid]

where the HECK does stroke come from, with regards to physics?

sorry, i'm quite confused with the question... are you asking what's the importance of the stroke in the entire process of hitting the cb?

From physics point of view, based on my stock knowledge (i hope other physics majors can confirm this):
FORCE= MASS X VELOCITY
or kilograms x meter/sqsecond

STROKE provides the VELOCITY
CUE is the MASS
The FORCE of impact between the cue & cb will now dictate how fast the ball will travel to the ob, with the cb as the new mass (velocity= force/mass) in the determining the force of impact between the cb & the ob

The cue tip's role is to be able to TRANSFER the kinetic energy of the cue to the cb as pure as possible. If the tip is soft there's more energy loss upon impact as a soft tip shrinks more, dampening the energy transfer, thus making the cb travel slower, unlike if it were a harder tip. Just like the effect of stock & racing springs on a car: stock springs are more quite/comfortable than racing springs but are not as "responsive" like the latter.

By the way, the cue on pendulum swing travels fastest at the bottom of the swing or when your hand is at 90deg angle with respect to the ground

If you're asking what's the use of a GOOD STROKE in the entire process, I believe that a good stroke (pendulum w/ follow through) allows the cue to travel & hit the cb at the desired path & point respectively. It's even a NATURAL motion to end the swing with a relaxed follow through, and you'll also be conserving your own energy unlike if you're to poke the shot. Moreover, a relaxed, pendulum swing travels faster than a muscled stroke (like in golf, bowling, etc)

Did I answer your question?

from http://galileo.phys.virginia.edu/outreach/8thGradeSOL/EnergyPendulumFrm.htm

A simple pendulum is an example of simple harmonic motion. It contiunes swinging back and forth. During this swinging, there is constant exchange between potential and kinetic energy. When a pendulum is the farthest up in its swing, it is at its maximum height which gives it maximum potential energy. At this same point in the swing, the pendulum is motionless for a fraction of a second because it is changing direction. Since the speed is zero, the kinetic energy is also zero. After the pendulum changes direction and begins swinging again, it is losing height, but gaining speed. This also means that the pendulum is losing potential energy, but gaining kinetic energy. When the pendulum reaches the very bottom of the swing, it is at its lowest point and greatest speed. This means that the pendulum has zero potential energy (with respect to its rest position) and maximum kinetic energy.

 

[Bob Jewett]

I think many people on this board are familiar with those high speed films of the cue hitting the cue ball. I think it was Bill Porter who said that no matter what they did during those tests they could not increase the contact time between the tip and the ball....

I think you are referring to the Jacksonville Project, in which video frame rates went up to 12,000 frames per second (compared to normal TV which is about 30 frames per second). I can respond about that project since I recorded the tests we did and edited the video down to 2 hours for distribution. A couple of things were found to increase contact time in general, including using a softer tip and hitting the ball farther off center.

Many assume that you need to increase contact time to increase "stroke". That's actually backwards, in that greatly increased contact time would probably reduce the amount of spin you could put on the ball on the ball according to one reasonable analysis.

If the stick is going faster when it hits the cue ball, the cue ball will go faster, all other things being equal.

If the tip hits the cue ball farther off-center, the cue ball will have less forward speed at the start, but there will be more spin in relation to the speed it does have.

How firm your grip is (for a normal human hand, anyway) at the instant of tip-to-ball contact, seems to have no effect on the shot. Whether the stick is accelerating or not at the instant of contact also seems to have no effect.

Great players have great "stroke" because they can consistently hit the cue ball well off-center and some of them can do that with great speed. See Mike Massey, Larry Nevel and Semih Sayginer for examples.

If you are looking for the secret of a great stroke, I'll be happy to tell it to you: there is no secret. If you manage to hit the ball as hard and as far off-center as any of those three players, you will get the same results. (Assuming your tip is properly prepared, etc., of course.)

If you are interested in the technical aspects of the Jacksonville Project and how to improve the "quality" of your stroke, those are covered in various articles at http://www.sfbilliards.com/articles/BD_articles.html and http://www.sfbilliards.com/misc.htm

 

[Kyros]

sorry, i'm quite confused with the question... are you asking what's the importance of the stroke in the entire process of hitting the cb?

From physics point of view, based on my stock knowledge (i hope other physics majors can confirm this):
FORCE= MASS X VELOCITY
or kilograms x meter/sqsecond

STROKE provides the VELOCITY
CUE is the MASS
The FORCE of impact between the cue & cb will now dictate how fast the ball will travel to the ob, with the cb as the new mass (velocity= force/mass) in the determining the force of impact between the cb & the ob

The cue tip's role is to be able to TRANSFER the kinetic energy of the cue to the cb as pure as possible. If the tip is soft there's more energy loss upon impact as a soft tip shrinks more, dampening the energy transfer, thus making the cb travel slower, unlike if it were a harder tip. Just like the effect of stock & racing springs on a car: stock springs are more quite/comfortable than racing springs but are not as "responsive" like the latter.

By the way, the cue on pendulum swing travels fastest at the bottom of the swing or when your hand is at 90deg angle with respect to the ground

If you're asking what's the use of a GOOD STROKE in the entire process, I believe that a good stroke (pendulum w/ follow through) allows the cue to travel & hit the cb at the desired path & point respectively. It's even a NATURAL motion to end the swing with a relaxed follow through, and you'll also be conserving your own energy unlike if you're to poke the shot. Moreover, a relaxed, pendulum swing travels faster than a muscled stroke (like in golf, bowling, etc)

Did I answer your question?

from http://galileo.phys.virginia.edu/outreach/8thGradeSOL/EnergyPendulumFrm.htm

Actually it is FORCE = MASS X ACCELERATION from Newton's second law. And just so you know... MOMENTUM = MASS X VELOCITY.

 

[Bob Jewett]

Actually it is FORCE = MASS X ACCELERATION from Newton's second law. And just so you know... MOMENTUM = MASS X VELOCITY.

More importantly for this purpose, momentum (and velocity, and quantity of spin) are proportional to the time integral of force that the tip applies to the cue ball. A hard tip will have a higher force for a shorter time and a soft tip will have a smaller force for a longer time, but they can both produce the same velocity and spin on the cue ball.

 

[Scaramouche]

Actually it is FORCE = MASS X ACCELERATION from Newton's second law. And just so you know... MOMENTUM = MASS X VELOCITY.

and since the mass of the cue is a constant, the only thing that changes is the speed of the cue at the time of contact.

And I guess that the speed depends on the rate of acceleration - fast for a hard hit, slow for a soft hit

 

[sicbinature]

I think many people on this board are familiar with those high speed films of the cue hitting the cue ball. I think it was Bill Porter who said that no matter what they did during those tests they could not increase the contact time between the tip and the ball.

If that is the case, where does the extra power in a stroke come from? I think most people would agree that it doesn't come from hitting the ball harder. For myself, I know that I get the most stroke on a ball when I'm hitting quite softly. It feels like I'm just moving my hand to my shoulder, no more effort than that.

So, if you can't increase contact time, and hitting harder doesn't seem to help, where the HECK does stroke come from, with regards to physics?

I know exactly what you are talking about. It feels like you didnt even hit the ball. You can seemingly barely hit it, and draw it the length of the table.

 

[elvicash]

And I guess that the speed depends on the rate of acceleration - fast for a hard hit, slow for a soft hit

In my opinion this is the answer.

I think the great power stroke is applied by the rate of change of the acceleration during the moment of the hit.

Many players come through the ball in a dead manner not accelerating the stick. This does not do anything positive or reproducible in a consistent manner.

Other affects are applied by coming through at a constant velocity. This can be used when you want to roll the ball such as high english.

The extreme stroke which has a lot of snap is applied in my opinion by raising the rate of acceleration at the moment of impact. This is accomplished in many sports by working the wrists at the moment of impact.

I believe in Statics and Dynamics class this was called a jerk.

Velocity - ft /s
Acceleration - ft / s^2
Jerk - ft / s^3

I do not know how you would measure it in any quantitive manner but I believe if you could measure this change in acceleration. What results is power being applied to the cue ball.

Remember a ball has two type of energies when it is struck both translational and rotational energy.

The people with the greatest stroke appear to be able to minimize the velocity of the cue ball in a translational speed while maximizing the rotational velocity.

Bob Jewett is correct as well as saying the best player can hit the most off axis the most consistently. Requires strong fundamentals and a good stroke.

Charlie Bryant is correct in saying come straight through the ball.

I propose only to add accelerate your acceleration if you want to add action.

Of course this depends on extremely sound fundamentals to be able to consistently focus the power into the cue ball.

 

[arsenius]

Thanks Bob and everyone who replied,

I was thinking of you not Bill Porter in my OP. I had tried a search but nothing came up, hence my mistake. I had a look at those Jacksonville articles and they were really interesting. But the results are also hard to accept based on my own experiences.

For example, the point about how firm your grip hand is. I've played with how firmly I hold the cue lately, because someone told me you could get more action on the cue ball that way. It seems like I can put a lot more spin on the ball with a firmer grip than a softer one. Does that mean I'm just moving my arm faster when I grip harder, and not realizing it? And so is the guy who told me, and the guy who told him? It's possible, but seems unintuitive.

Also, when I think of a draw shot. So many of us have tried to hit the ball hard and low, and usually it means that you get almost no draw. If I setup 20 long straight draw shots in a row, and hit 10 "hard and low" and 10 "firm, smooth and low" I would definitely expect better results from the second group. Even if I didn't pocket the object ball, causing the cue ball to go way off from straight back, I don't think I would see any massive draw on any of those shots. My point being that--without caring about consistency or ball pocketing--why can't I just execute a massive draw shot by hitting hard?

It's not that I don't believe the tests, because they make sense in the logical, scientific part of my brain. But it's very strange to find out that everyone's experience (including mine) seems to be wrong!

After writing this, it has gotten me to wondering. Did you guys do any experiments with the "smoothness" of a stroke? Did you try to replicate anything like a beginning player's stroke, a little herky-jerky? Did you try to replicate any common stroke flaws to see what happens when they occur? Does a smoother stroke naturally generate more power before hitting the cue ball, based on your findings? I'd be interested to hear about anything along those lines.

Also, I wanted to mention that I'm not looking for any easy answers. I'm actually pretty pleased with the power my stroke has (at least for the time being, I don't think that's the limiting factor in my game at the moment). I'm just curious about the science and the misconceptions so many players (like me) have.

 

[Bob Jewett]

... without caring about consistency or ball pocketing--why can't I just execute a massive draw shot by hitting hard? ...

The two main likely reasons are that your tip is not chalked properly and you do not hit far enough from center on the cue ball.

 

[Alex Kanapilly]

Thanks Bob and everyone who replied,

I was thinking of you not Bill Porter in my OP. I had tried a search but nothing came up, hence my mistake. I had a look at those Jacksonville articles and they were really interesting. But the results are also hard to accept based on my own experiences.

For example, the point about how firm your grip hand is. I've played with how firmly I hold the cue lately, because someone told me you could get more action on the cue ball that way. It seems like I can put a lot more spin on the ball with a firmer grip than a softer one. Does that mean I'm just moving my arm faster when I grip harder, and not realizing it? And so is the guy who told me, and the guy who told him? It's possible, but seems unintuitive.

Also, when I think of a draw shot. So many of us have tried to hit the ball hard and low, and usually it means that you get almost no draw. If I setup 20 long straight draw shots in a row, and hit 10 "hard and low" and 10 "firm, smooth and low" I would definitely expect better results from the second group. Even if I didn't pocket the object ball, causing the cue ball to go way off from straight back, I don't think I would see any massive draw on any of those shots. My point being that--without caring about consistency or ball pocketing--why can't I just execute a massive draw shot by hitting hard?

It's not that I don't believe the tests, because they make sense in the logical, scientific part of my brain. But it's very strange to find out that everyone's experience (including mine) seems to be wrong!

After writing this, it has gotten me to wondering. Did you guys do any experiments with the "smoothness" of a stroke? Did you try to replicate anything like a beginning player's stroke, a little herky-jerky? Did you try to replicate any common stroke flaws to see what happens when they occur? Does a smoother stroke naturally generate more power before hitting the cue ball, based on your findings? I'd be interested to hear about anything along those lines.

Also, I wanted to mention that I'm not looking for any easy answers. I'm actually pretty pleased with the power my stroke has (at least for the time being, I don't think that's the limiting factor in my game at the moment). I'm just curious about the science and the misconceptions so many players (like me) have.

There is no magic to it. The tip is on the cue ball for such a small amount of time, all that matters is where it hits the cue ball and how hard. It doesn't matter if you get the tip to the cue ball all herky jerky or smoothly, only that you make good contact (don't miscue) where you need to in order to execute the shot.

I would submit that you are losing control when you try to hit the cue ball hard... you are not hitting the cue ball where you want to. With the slower stroke you're hitting your target, or getting closer to it anyway. It's not easy to hit the cue ball where you want when you shoot hard, that's the trick.

You probably won't believe this but follow through doesn't matter either, assuming you do all the rest of it right.

 

[td873]

If that is the case, where does the extra power in a stroke come from? I think most people would agree that it doesn't come from hitting the ball harder.

Who are these "most people"? Oh, and what does "the extra power in a stroke" mean? I don't get it.

So, if you can't increase contact time, and hitting harder doesn't seem to help, where the HECK does stroke come from, with regards to physics?

What do you mean when you say "where does stroke come from, with regards to physics"? This is not a clear question to me. Anyone out there understand this?

Is this a DCP post in disguise?

-td

 

[Patrick Johnson]

... if you can't increase contact time, and hitting harder doesn't seem to help, where the HECK does stroke come from, with regards to physics?

From accuracy.

...I know exactly what you are talking about. It feels like you didnt even hit the ball. You can seemingly barely hit it, and draw it the length of the table.

That's not some mystical "stroke" ability that nobody can describe or understand. If you have trouble getting draw, it's because you don't hit the ball low enough, and that's often because your subconscious won't let you.

Watch carefully somebody who has trouble getting draw and you'll probably see that they point their tip low during aiming and practice strokes, but hit significantly higher on the shot stroke. Of course the harder they try to hit the worse their accuracy gets and the worse they do.

"Yeah," you say, "but if I'm just inaccurate, how come I don't hit too low half the time?"

Because your subconscious gets the dirty jobs, and in this case the job is to remember the humiliating times you scooped the cue ball off the table in front of everybody you were trying to impress, and never, ever let you do that again. So, especially when you're trying hardest to hit low and hard, your subconscious is working hardest to steer your stroke upwards to avoid yet another spectacular doofus moment.

The cure is to force yourself to learn to hit low on the cue ball without fear. I suggest watching the tip/ball contact on these shots, at least in practice, until you get more consistency. Try using a striped ball as the cue ball with the stripe turned horizontally so you can aim at the bottom edge of it (which is just about the maximum spin hit) and see from the chalk mark how close you came.

pj
chgo

 

[sicbinature]

That's not some mystical "stroke" ability that nobody can describe or understand. If you have trouble getting draw, it's because you don't hit the ball low enough, and that's often because your subconscious won't let you.


Not at all what I was talking about. I have no problem drawing a ball the length of the table. Sometimes though I stroke the ball and it is completly different. Like someone said, I believe it has to do with acceleration at contact.

 

[Deadon]

1. The energy from the cue is vectored. One in forward energy and one is rotational.
2. The farther you hit from the center, the more rotational energy(spin) you get and less forward energy(cb speed). The total energy doesn't change, just purportions.
3. Cue speed and mass determine the total energy, unless you have a tight grip.

 

[Patrick Johnson]

I have no problem drawing a ball the length of the table. Sometimes though I stroke the ball and it is completly different. Like someone said, I believe it has to do with acceleration at contact.

We'll have to agree to disagree. I believe it has nothing to do with acceleration and everything to do with tip/cue ball accuracy. However, the way you stroke does affect your stroke accuracy, and accelerating evenly ("smoothly") throughout the stroke sounds like it might help achieve greater accuracy and consistency.

The problem I have with the idea is that it redirects your attention toward one means of accomplishing your goal and away from the goal itself.

pj
chgo

 

[Andrew Manning]

I think many people on this board are familiar with those high speed films of the cue hitting the cue ball. I think it was Bill Porter who said that no matter what they did during those tests they could not increase the contact time between the tip and the ball.

If that is the case, where does the extra power in a stroke come from? I think most people would agree that it doesn't come from hitting the ball harder. For myself, I know that I get the most stroke on a ball when I'm hitting quite softly. It feels like I'm just moving my hand to my shoulder, no more effort than that.

So, if you can't increase contact time, and hitting harder doesn't seem to help, where the HECK does stroke come from, with regards to physics?

Reading your post, I think what you mean when you say "extra power" and "most stroke" is a lot of draw.

Others have answered your question correctly, but it sounds like you're confused and may need a short answer:

It's about how fast the stick is moving, and how low you hit. That's it.

Why you may be confused:

If you think you're hitting harder but not getting more draw, then either a)you're tensing your muscles and actually slowing down the cue AND/OR b)you're not hitting as low when you hit hard.

Power is about cue velocity. Action (draw) is about cue velocity + tip placement. All the crap about acceleration, smoothness, looseness/tightness of grip, etc., is all just about how to move the cue really fast at the moment of contact. The faster the cue moves, the harder the hit, and the more you move the cue ball.

Go ahead and take the advice you get about loose grips, acceleration, follow-through, and all the stuff people talk about here, and try it out and find what works for you, but keep in mind it's all just trying to achieve the goal of moving the stick very quickly through contact while retaining accuracy and precision.

-Andrew