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Post by golfbaka on Mar 4, 2010 7:32:04 GMT -5
Thanks for that foo.
The fact that we think that rocks and crystals are solid when in fact they were made up mostly of spaces in between atoms doesn't help me much when I run into a wall.
As humans, playing golf on planet earth, we are feel & can use these 'forces' to hit a small white ball with a bit of metal on the end of a stick better...
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Post by imperfectgolfer on Mar 4, 2010 10:04:38 GMT -5
Teddy,
You wrote-: "Well Jeff I also agree with the statement that the CP force causes the continuous change in direction, hence the orbiting ball. That does not mean there is a CF force, however."
I am delighted to learn that you now agree that a CP force is causing the continuous change in direction of an orbiting ball.
One final question regarding my original model, what is the "force" that causes the metal slugs in channels B, C and D to move to the peripheral end of the channel, and apply a constant pressure against the metal band at point Y - when the disc system spins clockwise at a finite speed? Also, what is the "force" that is causing the metal slug to stretch the metal spring in channel A in a direction that is radial (moving away from the center towards the circumference along the shortest path)?
Jeff.
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Post by jonnygrouville on Mar 4, 2010 19:25:55 GMT -5
The slugs has constant mass, so the force is caused by acceleration. The disc is spinning at a constant speed, but, from the point of view of the slugs, they are being accelerating in new directions all the time. The slug will then feel like it is constantly being pushed against the metal band.
The slug on the spring is subject to the same force, resisted by the same friction the others have overcome to make it to the outside and the resitance from the spring. It has moved outwards along the channel it is sitting in.
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Post by imperfectgolfer on Mar 4, 2010 19:49:18 GMT -5
Jonny,
Acceleration is not a force.
The fact remains that the slug is moving in a direction that is center-fleeing - and that's what is understood by the term CF force. It's a force that moves an object from the center of a circle to the periphery of the circle along the shortest path.
When it gets to point Y, and remains at that spot, the reason must be that the metal band (at the periphery) applies a stabilising counterforce to counteract the CF force so that the metal slug remains in the same condition - continuously orbiting in a circle of constant radius. The counterforce could be perceived to be the CP force - the same force that would keep a backseat passenger (constantly pressed against the right side door) riding in a constant circle when the car rides in a constant circle of fixed radius.
Consider another example.
There is a fairground ride where people stand inside a cylinder that spins. They are obliged to stand against the inside wall of the cylinder. When the spinning cylinder reaches a certain finite speed, they lower the floor, and that leaves the riders stuck against the inside wall of the cylinder without any floor support. What force is keeping the riders pinned against the inside of the spinning cylinder?
Jeff.
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Post by starretj on Mar 4, 2010 22:09:46 GMT -5
I really hate to get involved with this thread, but there are some misconceptions that I think need cleared up. A pure discussion of whether or not Centrifugal forces exists are boring, but there is some relevance to the golf swing.
First, Jonny didn't say that acceleration was a force, he stated that a force was caused by acceleration. This is entirely true as long as there is a mass involved, which obviously there is. Jeff, I don't understand why you called him out on this and then didn't even get what he said correct. Am I missing something?
As to what keeps a person pushed up against the wall in a spinning carnival ride when the floor drops, it is inertia. The person is trying to go straight and the wall of the ride is always turning into the person. If you have ever ridden one of theses rides, the force you feel is not in the middle of your back, it is on the lead side where the ride is turning into you.
The common phrasing as stated by Jeff, is that Centrifugal force is center fleeing. This usually is taken to mean that something is fleeing from the center. What is really true is that the center is trying to flee away from the mass. The mass has an amount of inertia that keeps it trying to either stay at rest or keep moving in a straight line with a constant velocity. If you stood in front of a wagon and attached a long spring to it and you grabbed the other end of the spring and started walking what do you think would happen? The spring would elongate by some amount while the wagon lagged behind the acceleration until equilibrium was met. Do you think that the wagon was fleeing from you? No. the reality is that you were fleeing from the wagon.
Now , why is this important to golf? Because the club head is never trying to flee from the center from pure rotation. If the club head is moving away from the center it is because of inertia or some force is acting upon it to move it away from the center or because the center is trying to flee from the club head.
Jimmy S.
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Post by jonnygrouville on Mar 4, 2010 23:25:14 GMT -5
I don't think this is boring! It is kind of fun.
I could probably have been clearer. It is the acceleration that causes the force on the mass. The disc is spinning at a constant rate, but the slug passengers are subject to constantly changing forces. These are due to the changes in their movement because of their confined condition in the wheel with the metal rim.
At the 'top' of your wheel as viewed from above, the slug will be moving left to right. A fraction of a second later, they will be moving a little bit down and a little bit less left to right. A quarter turn later, they will be moving only down. They have moved along the arc at a constant speed, but their speed relative to a fixed point has changed. Any change in speed is acceleration or deceleration and every acceleration or deceleration of a mass involves a force.
If you instantly removed the metal rim containing the slugs, they would fly out, but they would not fly out in straight lines away from the centre. The fairground ride passengers are subject to a force because of their confinement in the 'system'. Someone standing next to it is under no impetus to flee from the spinning centre.
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Post by imperfectgolfer on Mar 4, 2010 23:47:27 GMT -5
Jimmy,
You wrote--: "As to what keeps a person pushed up against the wall in a spinning carnival ride when the floor drops, it is inertia. The person is trying to go straight and the wall of the ride is always turning into the person. If you have ever ridden one of theses rides, the force you feel is not in the middle of your back, it is on the lead side where the ride is turning into you."
Thought-provoking comments. Could you please expand on this issue? What is the lead side? What would cause the person to move in a straight direction if he was simply standing in a stationary position when the cylinder started to rotate? What "force" is the spinning cylinder providing, and in what vectoral direction, and how does that keep the person plastered against the inside wall of the cylinder?
Jeff.
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Post by imperfectgolfer on Mar 4, 2010 23:55:05 GMT -5
Jonny,
I can understand that the slugs are constantly moving in a different direction - presumably in response to the fact the force-pressure from the side wall of the channel is constantly changing direction (as it follows a circular path).
Will the resultant path of the metal slug in the channel, as result of these constantly changing vectoral forces, not be center-fleeing and if the metal band at the periphery was suddenly removed, do you know for sure in which direction the metal slug would be propelled out of the channel - radially or along a tangent to the orbit?
Jeff.
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Post by TeddyIrons on Mar 5, 2010 2:02:16 GMT -5
For me it's much simpler to recognize that the CF is an effect, not a force - it is the result of the torque force that is being applied to spin the wheel and the CP force that couters it. Torque is a force that is changing direction continuously.
When a hammer thrower lets go of the hammer, from the moment it leaves his hands, does it fly out straight in front of him due to CF force?
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Post by jonnygrouville on Mar 5, 2010 3:44:28 GMT -5
Interesting question. I would say they will be pushed out by the inside wall of the channel behind them, so more tangental (give or take friction, etc.). It isn't the same as the radial motion away from the centre of opposing magnetic or electrical force. Otherwise, wouldn't those old siege engines, catapults and stuff just have thrown their boulders directly upwards?
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Post by imperfectgolfer on Mar 5, 2010 10:21:13 GMT -5
Teddy
Regarding the hammer thrower.
He is spinning in a circle and the ball is moving in a circular orbit. If the ball is moving along the circumference of a circle it has acquired angular momentum and considerable surface speed. When the thrower lets go of the chain, then the ball's acquired surface speed will be the force remaining and it will cause the ball to move off at a tangent to the circle. That's not a CF force.
Jeff.
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Post by imperfectgolfer on Mar 5, 2010 10:29:08 GMT -5
Jonny,
I actually suspect that the slug may move out longitudinally/radially because it is jammed against the metal band that lies at the circumference of the circle. The slug is exerting a force against that metal band, and if that band suddenly disappears, why wouldn't the slug move in a radial direction, rather than at a tangent to the orbit.
A cannon ball leaves the channel of a cannon in a direction that is along the longitudinal direction of the cannon. Not the same situation as my model, and I therefore wonder if the analogy is appropriate.
Those siege catapults slung their load at an angle, and not radially from the center. Therefore, the analogy may not be useful.
Jeff.
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Post by jonnygrouville on Mar 5, 2010 19:50:25 GMT -5
Jeff,
You're right. That probably wasn't best. I was trying to think of some example with a huge levered catapult.
What about if you remove the rim from the wheel and put all the slugs back in the centre, then span the wheel so the slugs moved from the centre to the edge and then released. If it took a quarter turn for this to happen, the slug in the tube that starts pointing at 12 o'clock will leave the wheel when it is pointing at 3 o'clock.
I think we are back to the passenger in the car being pushed against the door. The force against the band is caused by the turning motion, the slug being pushed around and wanting to escape. Without the band, I think this would continue to push the slug more downwards towards 6 o'clock instead of flying out towards 3 o'clock.
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Post by starretj on Mar 6, 2010 8:55:33 GMT -5
Jonny, this has been a good thread and hasn't turned out like most of the CF debate threads over the years.
I was hoping that my last thoughts in my previous post would have sparked more discussion. Maybe I didn't make my thoughts clear or maybe they just don't make any sense. I will try and state my case again and see if it sparks any response. I don't believe that the club head is fleeing from the center of rotation. I believe that we insert some energy into the club so that it has velocity and direction towards the ground. To get the club head and face to the ball we then manipulate the handle of the golf club, mostly with torques.
Does anyone agree or disagree? Jeff, I would think that your thoughts about this and your ideas presented in the thread about hand paths and the straight line delivery and pulley size would probably lead to some interesting insight.
The only reason that I bring this up is that I think it is very important to our understanding of the swing and what a golfer actually does or should do to hit the ball effectively. If you believe that the club head is fleeing from your center and will therefore want to go to the ball from 'CF' because you are rotating, then your intentions will be a lot different from someone who is thinking about getting some speed into the club and then manipulating the handle to get the club face traveling the way you want it to. I do not believe that this is the difference between hitting and swinging.
Jimmy S.
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Post by imperfectgolfer on Mar 6, 2010 10:09:39 GMT -5
Jimmy, I think that we may probably agree about what causes the clubhead to release in a full golf swing, and it's not a CF (center-fleeing) force. I am not even impressed by my own model that reputedly attempts to demonstrate the presence of a CF force. It's too incomplete and potentially full-of-holes. I prefer to use the term "CF release" in a very vague sense to indicate the type of release that occurs in a double pendulum swing model and the endless belt system, and one can explain the passive release without invoking a center-fleeing force. My favorite explanation is this one - by nm golfer. perfectgolfswingreview.net/New%20Millennium%20Golf%20Science.htmBasically, he states that when the hand arc changes direction, it causes the club to develop angular momentum because the pull-force at the grip end of the club is at an angle to the COG of the club, which resides at the peripheral end of the club near the clubhead. With each change in hand direction, the club develops more angular momentum, which adds to the amount of angular momentum the club has already acquired. Jeff.
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