The Myth of Top Spin???

[mikepage]

The entity is moving east. The same concept could be related to above and below the axle line as well as above and below the track base.

But I think, (not sure though) if a part of the train was actually moving west, on a long trip you might lose it.

OK fair enough.

How's this

A point on the regular part of the wheel moves forward like a hopping frog.

A point on the flange moves forward like a hopping frog who takes a step backwards after each hop --like a retrograde motion

 

[DoubleA]

Part of the flange is actually moving west.

Check your physics texts, you will see that the flange actually has an easterly velocity. When the train completes it's journey, all parts of the train will have moved to the east.

 

[DoubleA]

8-baller is right.

The tip is storing energy like a spring does as it's compressed.

Halfway through the tip-ball contact , when the tip is fully compressed, the ball and stick are moving at the same speed. During the whole second half the ball is speeding up and the stick is slowing down. The tip is releasing it's stored energy during this part.

By the time the collision is over, the ball is going about 50% faster than the stick ever was.

I would be interested in knowing what physics books you get your information from. You can never store more energy than you input. This is laughable, check your laws of motion. Since these laws and logic seem to have been replaced with a need to be "right", I respectfully submit this as my last post.

 

[mikepage]

I would be interested in knowing what physics books you get your information from. You can never store more energy than you input. This is laughable, check your laws of motion.

I'm content with my physics.

I don't understand your objection.

 

[spoons]

I'm not a physics guru, but wouldn't the flex of the shaft transfer more energy to the cue ball than the compression of the tip?

 

[branpureza]

I'm content with my physics.

I don't understand your objection.

It's the same principle as dropping a bouncy ball on the ground... it'll never reach the height you dropped it from... even though it compresses, just like the tip of your cue.

 

[mikepage]

Check your physics texts, you will see that the flange actually has an easterly velocity. When the train completes it's journey, all parts of the train will have moved to the east.

I think you're missing the point of the problem.

OF COURSE the average velocity of anything attached to the train is 60 mph east.

But a point on the outer edge of the wheel oscillates between 0 mph and 120 mph east and is never moving west.

A point on the flange oscillates between, say, 10 mph west and 130 mph east. So it is moving west some of the time.

 

[Southpaw]

Doesnt the density of the object ball it contacts make a difference? If the object ball is heavier, wouldnt it absorb more than a lighter ball?

Southpaw

 

[mikepage]

It's the same principle as dropping a bouncy ball on the ground... it'll never reach the height you dropped it from... even though it compresses, just like the tip of your cue.

Yes, the collision is inelastic. I agree with this.

 

[mikepage]

I'm not a physics guru, but wouldn't the flex of the shaft transfer more energy to the cue ball than the compression of the tip?

No, most of the action is in the tip. Though if you cut the tip and ferrule off and hit the ball with wood, the wood would do the same thing.

And normally when people talk about "flex" of a cue they mean bending--and that bending energy is mostly lost. It's the compression along the stick that would be doing the action.

 

[av84fun]

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.

Understood. The disconnect is with respect to the matter viewed as a chain of events.

Without the initial movement of the cb...call it what you will....the cb would have remained in place...it never would have impacted the ob...iand it would never have "resumed" motion that it had never begun.

So, in spite of certain protestations to the contrary, it is impossible and illogical to state that "forward momentum" has nothing to do with the issue, just as it would be equally illogical for a lawyer to plead that his client pulled the trigger but that did not "cause" the victim to die.

True understaning, AFAIC...results from a complete understanding of the entire chain of events...not mere focus on any individiual component.

If the POOL PLAYER, wants to create more forward RPMs so that the CB will travel farther after OB contact, then he must impose greater linear momentum to the shot (assuming constant tip contact height) and therefore, that linear momentum is absolutely a factor in learning that pool shot just as linear momentum (or velocity...don't know and don't care) is a factor in the equation for angular momentum.

The opposite of the LEARNING sequence would be to say..."Oh, don't worry about how hard you hit the CB or at what height above center because it's going to come to a dead stop anyway and angular momentum will get you where you need to go.

Again...once more for feeling...I am talking about the process of learning to shoot pool not the process of passing a physics exam. In fact, with no offense intended to anyone, I think that this and many other threads like it demonstrate quite clearly that delving too deeply into physics creates more confusion than understanding.

Here's the deal about post-impact CB travel. The harder you stroke the sucker with high english the further it will roll and if you shoot hard enough the sum***** will scamper forward like a damn rabbit bein' chased by a dog.

Talk to most students about angular momentum and they will ignore you...if not punch you in the nose!

(-:

Regards,
Jim

Parallels between straight-line motion and rotational motion
Let's take a minute to summarize what we've learned about the parallels between straight-line motion and rotational motion. Essentially, any straight-line motion equation has a rotational equivalent that can be found by making the appropriate substitutions (I for m, torque for force, etc.).

http://physics.bu.edu/~duffy/py105/AngularMo.html

 

[av84fun]

Your mileage may vary, but I usually find that when I don't understand what Mr. Jewett is saying, it's because he's a step or two ahead of me.

He will agree there's no part of a moving car going backwards, and therefore as you said, a car can't kick a stone backwards (so long as it's not peeling out, that is).

But a train differs from a car in a significant way. There's the flat bottom of the train wheel that sits on the rail, and then there's a part of the wheel called the flange that sticks down lower on the inside of the rail (to keep the wheel from sliding out) In other words if the business part of the wheel is a circle of 40 inch diameter, then the wheel with the flange is a circle of, say, 46 inch diameter. The portion of the flange below the rail is moving west.

Interesting!! In suggesting the wheel I was....ummmmm....on the right track! (-:

But paint a dot on that portion of the flange and take stop-motion pictures of that wheel with the train moving east at 60 mph and the spot will be shown to have moved east after X time/distance.

For how long/far does it move west???

(-:
Jim

 

[av84fun]

The shot started with Topspin so its a topsin shot-sorry.If you were a great draw shot maker but couldnt follow, you couldnt make the shot. and what do you get from normal roll into a rail a normal rebound.

Not much and not for long and AFAIK, natural roll has resumed before CB contact excpet on very close shots.

On the contrary, we all can draw the CB back when striking it at the head spot with an OB jawed in an opposite corner, which is prima fascia evidence that the CB is spinning backward even at that long distance.

I would like to see slo mo video proving that the CB can sustain forward roll greater than that explained by "normal roll" i.e. roll with no slippage between CB and cloth such as exists with a draw shot.

Of course we can SEE the forward rotation of the CB on a follow shot but I do not believe the human eye can tell whether that is purely natural roll or "top spin" which is commonly defined as forward spin in excess of non-slipping forward roll.

Possibly the misunderstanding relates to the definition of "topspin." Many definitions simply say it is forward motion about the horizontal axis which certainly includes and ball rolling forward on the table.

But then even center ball or shots like a drag draw become "topspin" shoots.

So, before the discussion proceeds any further I think we have to define our terms. I suggest that "topspin" is spin at a greater rate than that which would be explained by normal, non-slipping roll and that being the case, I would have to see slo mo video before I believe such spin can exist for anything other than very short distances.



Regards,
Jim

 

[Jal]

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?

Jim, I think we see your point. But it's a wee bit misleading, imo. It suggests that the CB sort of plows through and simply continues with a fair amount of its pre-impact velocity (which I know you're not saying).

An off-center hit produces both linear speed and spin. The linear speed accompanies the spin, and the spin accompanies the speed. The spin is not caused by the speed anymore than the speed is caused by the spin (we're not talking about any additional topspin picked up along the way here). The force applied by the stick causes the speed, and the torque applied by the stick causes the spin. Though intimately related, these are really two different animals. No?

And we all agree, it's the spin that causes the CB to move forward.

Sorry to nitpick, but I think your way of stating it will get you into many arguments. (Patrick may even object.)

Jim

 

[av84fun]

And that's why water spins the other way in toilets below the equator when ya flush em too! Right?

As I am sure you know...that is a myth. It is often attributed to Corliolis Force which does rotate LARGE bodies in opposite directions its effect is orders of magnitude too weak to have anything to do with toilet bowl drainage.

(-:

Jim

 

[av84fun]

deleted............

 

[av84fun]

I'm content with my physics.

I don't understand your objection.

I don't either. The "spring effect" on drivers in golf is both well known and highly regulated under the rules.

Regards.
Jim

 

[ShootingArts]

this is the heart of the matter

Here's the deal about post-impact CB travel. The harder you stroke the sucker with high english the further it will roll and if you shoot hard enough the sum***** will scamper forward like a damn rabbit bein' chased by a dog.

Jim

Jim,

I whacked out far more of your post than I kept but this is the heart of the matter. We can simply "blackbox" the "why" of how things work on the pool table and just understand when and how they work. Some of the best instructors have a very in-depth understanding of the "why". It seems that most of the great pool players are clueless and totally uninterested in the "why." Can you see Efren, Francisco, and Alex sitting around arguing why the balls behave like they do? Dollars to donuts if they talk about past happenings on the pool table at all the hands are flying and they are explaining great shots that went in or great shots that should have went in but didn't like bench racers everywhere.

The threads discussing theory are interesting and there were some things I will have to mull over and decide if they stand close scrutiny that I read in this thread. However, at the end of the day I know how to make the cue ball take off after the hit like a scared jackrabbit. That is what will get this country boy out of a bind sometimes unless I choke while considering if what I have done dozens of times before is physically possible in light of what I have read. Ignorance can be bliss . . . . and profitable!

Hu

 

[av84fun]

Jim, I think we see your point. But it's a wee bit misleading, imo. It suggests that the CB sort of plows through and simply continues with a fair amount of its pre-impact velocity (which I know you're not saying).
An off-center hit produces both linear speed and spin. The linear speed accompanies the spin, and the spin accompanies the speed. The spin is not caused by the speed anymore than the speed is caused by the spin (we're not talking about any additional topspin picked up along the way here). The force applied by the stick causes the speed, and the torque applied by the stick causes the spin. Though intimately related, these are really two different animals. No?

And we all agree, it's the spin that causes the CB to move forward.

Sorry to nitpick, but I think your way of stating it will get you into many arguments. (Patrick may even object.)

Jim

With GREAT respect...no...There is nothing in my explanation that remotely suggests that. In fact, I STIPULATED that the CB stops and is made to roll forward by a VERSION of momentum.

IMHO, as I think this thread proves the greater confusion arises from the discussion about what VERSION of momentum is the driver...angular or linear/straight line.

I think that people of all intellectual capacities will understand that the guy who pulled the trigger killed the victim and would reject the notion that that isn't true because the bullet did.


Besides, the whole matter is a hijack since the OP's question was whether we believe the author of the article which stated that OVERspin does not exits which is an entirely different topic.

And LOL on Patrick objecting but hey...he thinks that "reasoned thought" must be "rational" so what can ya do!

(-:
Jim

 

[av84fun]

There Ya Go!

Jim,

I whacked out far more of your post than I kept but this is the heart of the matter. We can simply "blackbox" the "why" of how things work on the pool table and just understand when and how they work. Some of the best instructors have a very in-depth understanding of the "why". It seems that most of the great pool players are clueless and totally uninterested in the "why." Can you see Efren, Francisco, and Alex sitting around arguing why the balls behave like they do? Dollars to donuts if they talk about past happenings on the pool table at all the hands are flying and they are explaining great shots that went in or great shots that should have went in but didn't like bench racers everywhere.

The threads discussing theory are interesting and there were some things I will have to mull over and decide if they stand close scrutiny that I read in this thread. However, at the end of the day I know how to make the cue ball take off after the hit like a scared jackrabbit. That is what will get this country boy out of a bind sometimes unless I choke while considering if what I have done dozens of times before is physically possible in light of what I have read. Ignorance can be bliss . . . . and profitable!Hu

yeah I WISH I had been able to go to Charlie's instruction session with Efren, Busta etc.

If I had asked Efren to explain conservation of energy to me I'm sure he would have said that it comes from getting plenty of sleep!

(-:

Jim