Squirt. End Mass and Cue Flexibility.

wrong...

john coloccia said:

Premise 1 is wrong. The cue ball can't accelerate away from the shaft unless something is pushing on it, i.e. the shaft. In fact, it starts to decelerate due to friction immediately after the shafts stops pushing on it. It's the shaft that decelerates, mostly due to hitting the cue ball. Said another way, there's a transfer of momentum, one of those convenient quantities that is always conserved.

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It accelerates away BECAUSE the tip/shaft is decelerating from imparting the force on the ball.

The tip can't decompress unless the ball is moving away from it...acceleration is all relative....the ball is accelerating relative to the tip/shaft which is what matters in this discussion.

so try again...

Jaden

Jaden said:

so try again...

Jaden

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No thanks.

Jaden said:

premise 1) the ball is accelerating away from the tip/shaft before the tip/shaft moves laterally away

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This premise has two problems. First, acceleration (an increase in speed) can occur only with force; therefore, the CB can accelerate only while force is acting from the tip. Secondly, if the tip/shaft moves away laterally after the tip leaves the CB, it is because the tip/shaft was given lateral speed during contact (while lateral forces were acting). It is the momentum (mass * speed) of the endmass that makes the tip and shaft move away from the CB after impact. Now, any flex energy still stored in the end of the shaft after tip release will also cause some post-release vibration (as is evident in the slow motion videos), but this is independent of (and much smaller in amplitude than) the larger-scale tip/shaft motion away from the ball (due to the endmass lateral momentum). Again, all of this is explained, illustrated, and demonstrated on the following resource page:

what causes squirt

squirt endmass and stiffness effects

cue flex and vibration

This premise being wrong makes anything else based on this premise also wrong.

I hope that makes sense and helps,
Dave

no problem...

john coloccia said:

No thanks.

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No one has to try again...

concession is fine...

I'm almost done here anyways...There's no point in a one way argument..

and I've already shown to anyone willing to look what the case really is.

Jaden

please stop obfuscating...

dr_dave said:

This premise has two problems. First, acceleration (an increase in speed) can occur only with force; therefore, the CB can accelerate only while force is acting from the tip. Secondly, if the tip/shaft moves away laterally after the tip leaves the CB, it is because the tip/shaft was given lateral speed during contact (while lateral forces were acting). It is the momentum (mass * speed) of the endmass that makes the tip and shaft move away from the CB after impact. Now, any flex energy still stored in the end of the shaft after tip release will also cause some post-release vibration (as is evident in the slow motion videos), but this is independent of (and much smaller in amplitude than) the larger-scale tip/shaft motion away from the ball (due to the endmass lateral momentum). Again, all of this is explained, illustrated, and demonstrated on the following resource page:

what causes squirt

squirt endmass and stiffness effects

cue flex and vibration

This premise being wrong makes anything else based on this premise also wrong.

I hope that makes sense and helps,
Dave

Click to expand...

You're obfuscating the reality...

Answer this. DOES the tip decompressing mean that the ball is traveling away from the tip/shaft?

Because if it does, then that means that the ball is accelerating away relative to the tip/shaft. relative to the table (which is what you are describing here) doesn't make one iota of difference here.

This means that once the tip starts decompressing, the ball CANNOT be directly acting on the tip/shaft.

and THAT means there has to be another force causing the tip/shaft to move laterally because the video clearly shows that the tip begins to decompress before the tip/shaft moves laterally.

So if it isn't stored kintetic energy in the shaft (which you've ALREADY acknowledged is there) then what is it?

Jaden

Jal said:

Between yourself and Dr. Dave, I believe your earlier question has been answered

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Yes, thanks to you both, I now have a coherent picture of the interaction in my brain.

Thank you kindly.

Jaden said:

premise 1) the ball is accelerating away from the tip/shaft before the tip/shaft moves laterally away from the initial line of travel which is evident from high speed video because the tip is decompressing prior to lateral tip/shaft movement.

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If you believe premise 1, where does the cueball acquire spin? If the cue stick does not move laterally until after contact is terminated, then during contact the ball has not begun to spin. If it hasn't begun to spin, no torque could have been applied during contact. No torque, no spin.

Thank you kindly.

Jaden said:

Answer this. DOES the tip decompressing mean that the ball is traveling away from the tip/shaft?

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Depends on what you mean by that. The tip will start decompressing somewhere in the middle of the tip-ball interaction (contact time). High speed photos (see LaMas's post) seem to show that the compression is almost over by the time the contact is over. They also show the tip moving laterally.

Because if it does, then that means that the ball is accelerating away relative to the tip/shaft. relative to the table (which is what you are describing here) doesn't make one iota of difference here.

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In any reference frame, acceleration only occurs in the presence of a force. Thus the cue ball is only accelerating when in contact with the cue stick. Or if you prefer another reference frame, the cue stick is only decelerating (other than friction forces from the grip) when in contact with the cue ball.

Certainly the cue ball is MOVING away, but it isn't accelerating. Cue balls only slow down after they leave the cue tip. Surely, this can't be the bone of contention here.

This means that once the tip starts decompressing, the ball CANNOT be directly acting on the tip/shaft.

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Sure it can. The ball is moving away from the cue (butt), but so is the front of the tip, that is what decompression means here. That means that contact can still be occurring, and forces can still be acting.

and THAT means there has to be another force causing the tip/shaft...

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What other object is available to produce a force in that direction?

...to move laterally because the video clearly shows that the tip begins to decompress before the tip/shaft moves laterally.

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Not to my eyes. The still photos (from video) with the yellow ball, CLEARLY (to my eye) have the shaft moving laterally (down in the photo) Not only before decompression, but actually in the compression phase, and seems to be roughly constant throughout the contact time.

So if it isn't stored kintetic energy in the shaft (which you've ALREADY acknowledged is there) then what is it?

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What do you mean by 'stored kinetic energy'? Kinetic energy is just a way of describing the ability of moving objects to create a force. 'stored' energy would be some kind of potential energy, which is defined as being due to position in a field (i.e. not speed).

This conversation will be a lot easier if we are all using the same words to mean the same things.

Thank you kindly.

I'll address these when I get home

I'm playing in a tourney today and addressing these from my phone becomes cumbersome so I'll address them tonight when I get home.

Just remember that contact can occur after the force has been imparted and that the force cannot be imparted once the ball starts to move away from the tip which happens as soon as the tip starts to decompress.

Jaden

Jaden said:

I'm playing in a tourney today and addressing these from my phone becomes cumbersome so I'll address them tonight when I get home.

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Seriously, no rush.

Just remember that contact can occur after the force has been imparted and that the force cannot be imparted once the ball starts to move away from the tip which happens as soon as the tip starts to decompress.

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Why would I want to 'remember' something that I don't think is even true? And is one of the points of contention.

Take as an easy example, a rubber ball bouncing on the floor. If no force can be imparted to the ball once decompression starts, what exactly is pushing the ball back into the air? Prior to that, the ball was moving toward the floor.

Thank you kindly.

Jaden said:

dr_dave said:

This premise has two problems. First, acceleration (an increase in speed) can occur only with force; therefore, the CB can accelerate only while force is acting from the tip. Secondly, if the tip/shaft moves away laterally after the tip leaves the CB, it is because the tip/shaft was given lateral speed during contact (while lateral forces were acting). It is the momentum (mass * speed) of the endmass that makes the tip and shaft move away from the CB after impact. Now, any flex energy still stored in the end of the shaft after tip release will also cause some post-release vibration (as is evident in the slow motion videos), but this is independent of (and much smaller in amplitude than) the larger-scale tip/shaft motion away from the ball (due to the endmass lateral momentum). Again, all of this is explained, illustrated, and demonstrated on the following resource page:

what causes squirt

squirt endmass and stiffness effects

cue flex and vibration

This premise being wrong makes anything else based on this premise also wrong.

I hope that makes sense and helps,
Dave

Click to expand...

DOES the tip decompressing mean that the ball is traveling away from the tip/shaft?

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Yes. The CB should be moving faster than the tip and shaft by the time the force between the tip and CB start to diminish, at which time the tip starts springing back.

Jaden said:

This means that once the tip starts decompressing, the ball CANNOT be directly acting on the tip/shaft.

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Incorrect. If the tip is still compressed (even during the decompression stage), there is still a force acting between the tip and ball. Only when the tip is no longer compressed is there no longer any force acting on it.

Jaden, the following set of images from the best video we currently have available should help you visualize the motion of the tip, shaft and CB during and slightly after impact. The red line marks the initial position of the top of the shaft and initial tip contact point, and the red dot marks the initial position of a distinct point on the ball. They are in the same positions in each successive image.


These images are totally consistent with all of the physics I have been describing and illustrating. It is clear that the tip and shaft move down (laterally) away from the CB as the CB moves forward with increasing speed and spin during the entire period of tip contact.

Regards,
Dave

Semantics.

When a force that is used to constrain (restrict) another force is removed, then it no longer can apply force.

The force was applied during the TIME of constraint or restriction.

Once that retraining/constraining force is released, the stored energy, or force 'built up' from the constraint can then apply 'itself'.

Relativity & Time.

Jaden said:

It accelerates away BECAUSE the tip/shaft is decelerating from imparting the force on the ball.

The tip can't decompress unless the ball is moving away from it...acceleration is all relative....the ball is accelerating relative to the tip/shaft which is what matters in this discussion.

so try again...

Jaden

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john coloccia said:

No thanks.

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Wise man!

(....wish I was that smart)

Jim

When the shaft is bowing out & the tip is bending inward, the tip & the bowed shaft are not restricted from ALSO moving out as a unit in that flexed state.

Over isolation can be & seemingly is an issue.

Corwyn_8 said:

Take as an easy example, a rubber ball bouncing on the floor. If no force can be imparted to the ball once decompression starts, what exactly is pushing the ball back into the air? Prior to that, the ball was moving toward the floor.

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Great example. If this doesn't convince Jaden that this part of his scenario is wrong, hard to imagine what will.

Jim

ENGLISH! said:

When the shaft is bowing out & the tip is bending inward, the the tip & the bowed shaft are not restricted from ALSO moving out as a unit in that flexed state.

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So true!

Jim

Jal said:

Great example. If this doesn't convince Jaden that this part of his scenario is wrong, hard to imagine what will.

Jim

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Jim,

If a ball is squeezed in from every point of its perimeter...

& then if all of those directional forces are simultaneously released all at once...

does the ball get propelled in any direction from the stored up energy force of its compression...

Or does it just restore itself to 'equilibrium' with no movement in any direction... other than gravity pulling on it.

If the ball is moving, as in Corwyn's example, the force is in the movement(velocity) of the mass of the ball... & in a direction.

When an 'immovable' fixed floor or wall stops the ball's movement & the ball compresses, that compression force is 'released' or redirected in another direction.

If it were a steel canon ball instead of a pliable rubber one it would do damage to the wall or floor. If a steel ball could be compressed as much as a rubber ball it would rebound at a much higher velocity than a rubber ball. Think of a sponge rubber ball & a regular golf ball being hit by a driver.

The cue ball has no force other than its static mass & that ability to resist & accept a force & its potential compression & rebound ability.

The force comes from the moving speed of the mass of the cue stick.

AND

The resistance of the moving mass, the cue stick, BY the ball, it's that 'force' that causes the more pliable material of the tip & the shaft to compress. The CB, not being fixed, can not hold that compression & is moved away by BOTH the momentum force of the moving mass of the cue stick AND the compression 'release' of both the tip & the shaft...

That 'force' of the ball's static mass causes the tip & the shaft to compress.

That compression force is then applied back to the mass of the ball that restricted the force of the moving mass of the cue stick.

There is much going on during contact. It is not just a simple collision like that of two(2) very much less pliable, 'statically' hard phenolic balls.

Like Renfro/Chris said, treating it as such is a mistake.

Just a few short years ago all of the scientific testing said that a very hard rigid material driver head would result in more compression of the newer more firm golf balls & yield more distance. It basically did that compared to the softer wood heads even with hard plastic inserts & the more hard but still relatively 'soft' steel heads compared to the more hard materials.

Then the theory changed. A hard 'center' material mounted with a more pliable perimeter would yield more distance by BOTH compressing the ball AND trampolining the ball too.

That method yielded so much more distance that the USGA had to place limits on the COR of golf clubs heads. The same had to be done for synthetic material baseball bats.

That theory & technology made the contact of hitting a golf ball more complex than it ever was before when the heads were only of a more solid rigid material.

Again, this is just food for thought for anyone interested.

ENGLISH! said:

When the shaft is bowing out & the tip is bending inward, the tip & the bowed shaft are not restricted from ALSO moving out as a unit in that flexed state.

Over isolation can be & seemingly is an issue.

Click to expand...

Thanks for the Green Rep, Dr. Dave.

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