A HELPING HAND

[mandrin]

In two succeeding posts by ThinkingPlus

Physics 101 answer
-------
Basically, since this is an elastic collision, momentum is not strictly conserved, but it is close enough for our purposes. You can also approximate Mclub with the mass of the clubhead alone since the impact interaction occurs over such a short time.

Newton's 1st Law
-----
Lag pressure maintained through impact will result in a collision that is more inelastic (less lossy) than if one had a clubhead moving with a constant velocity (my assertion, et al.).


In the first post it is clear that the clubhead is considered a free mass. (this is against TGM philosophy.) In the second post it is however just the opposite. An obvious and very clear contradiction in two adjacent posts.

Also in the first post it is stated that in an elastic collision momentum is not conserved. This is a gross error. Momentum is ALWAYS conserved, both in elastic and inelastic collisions.

Moreover in the second post it is stated that there is less loss in a more inelastic collision. This is a gross error. It is just the opposite. Kinetic energy is conserved in an elastic collision and is not in an inelastic collision.

 

[mandrin]

A helping hand

[SIZE=-2]Conservation of Energy is what happens at the ball.
Part1. Angular momentum is about what happens on the way to the ball. [/SIZE]

Very peculiar statements. The simple scientific truth is that effort expended by the golfer from the top creates motion and associated with it there is generated simultaneously kinetic energy and angular momentum. The angular velocities increase as the downswing proceeds and with it also the kinetic energy and the angular momentum.

[SIZE=-2]The longer you sustain the lag, the smaller the wheel, and like the ice skater pulling in her arms, the faster the clubhead mass must travel to conserve angular momentum.[/SIZE]

Angular momentum is not conserved in a golfer’s downswing since there is not any to be conserved to start with. It is being generated throughout the downswing by the effort expended by the golfer. Whilst being continuously generated it is redistributed due to unfolding of the club.

In Part2 impact interval is discussed and golf2much states that much of the kinetic energy of the clubhead is transferred to the ball and formulates this as:

[SIZE=-2](½ m1*v1^2 - losses) (clubhead) = ½ m2*v2^2 (ball)[/SIZE]

where the losses are referring to the small losses due to deformation of the ball and the clubface during impact. This formulation is erroneous. The clubhead still has an appreciable velocity after impact and the formulation should have been:

[SIZE=-2]½ m1*v1^2 (clubhead) = ½ m1*u1^2 (clubhead) + ½ m2*u2^2 (ball) + losses [/SIZE]

 

[rundmc]

[SIZE=-2]Conservation of Energy is what happens at the ball.
Part1. Angular momentum is about what happens on the way to the ball. [/SIZE]

Very peculiar statements. The simple scientific truth is that effort expended by the golfer from the top creates motion and associated with it there is generated simultaneously kinetic energy and angular momentum. The angular velocities increase as the downswing proceeds and with it also the kinetic energy and the angular momentum.

[SIZE=-2]The longer you sustain the lag, the smaller the wheel, and like the ice skater pulling in her arms, the faster the clubhead mass must travel to conserve angular momentum.[/SIZE]

Angular momentum is not conserved in a golfer’s downswing since there is not any to be conserved to start with. It is being generated throughout the downswing by the effort expended by the golfer. Whilst being continuously generated it is redistributed due to unfolding of the club.

In Part2 impact interval is discussed and golf2much states that much of the kinetic energy of the clubhead is transferred to the ball and formulates this as:

[SIZE=-2](½ m1*v1^2 - losses) (clubhead) = ½ m2*v2^2 (ball)[/SIZE]

where the losses are referring to the small losses due to deformation of the ball and the clubface during impact. This formulation is erroneous. The clubhead still has an appreciable velocity after impact and the formulation should have been:

[SIZE=-2]½ m1*v1^2 (clubhead) = ½ m1*u1^2 (clubhead) + ½ m2*u2^2 (ball) + losses [/SIZE][/quote]


anyway . . . I respect your scientific knowledge and stuff so could you help me understand something.

In your estimation . . . what is Lag? Is it anything? If there is truly such a thing when does it begin?

My thoughts were this if the club is moving back and you start moving forward then the "lag" is loaded in your hands. I may have this wrong but I remember something that you said and I may be misquoting you . . . basically the clubhead is free-wheeling through impact as if it were not attached to the shaft. If I haven't misquoted you, would that be the same for the left arm too?

Above you said "Angular momentum is not conserved in a golfer’s downswing since there is not any to be conserved to start with. It is being generated throughout the downswing by the effort expended by the golfer. Whilst being continuously generated it is redistributed due to unfolding of the club." Once the initial effort to make the club change directions in the transition is made how much effort is needed if one is relying on CF (and you can certainly shoot that down if you like . . . is that not the "ficticious" force)? So once the club is moving down how much effort is required to sustain its velocity?

Thanks!

RunRichieBucketTrickdawgCrewsdaddyPunchingBag

 

[golfbulldog]

anyway . . . I respect your scientific knowledge and stuff so could you help me understand something.

In your estimation . . . what is Lag? Is it anything? If there is truly such a thing when does it begin?

My thoughts were this if the club is moving back and you start moving forward then the "lag" is loaded in your hands. I may have this wrong but I remember something that you said and I may be misquoting you . . . basically the clubhead is free-wheeling through impact as if it were not attached to the shaft. If I haven't misquoted you, would that be the same for the left arm too?

RunRichieBucketTrickdawgCrewsdaddyPunchingBag[/quote]


Bold by me

I think ( again not physics guy) that lag ties in with the inertial forces topic that Mandrin started. It seems that lag pressure is felt at loading when the inertial forces ( recative forces) are created by a longitudinal pull. Is this the way that these mysterious Inertal forces manifest themselves?

 

[mandrin]

lag

anyway . . . I respect your scientific knowledge and stuff so could you help me understand something.

In your estimation . . . what is Lag? Is it anything? If there is truly such a thing when does it begin?

My thoughts were this if the club is moving back and you start moving forward then the "lag" is loaded in your hands. I may have this wrong but I remember something that you said and I may be misquoting you . . . basically the clubhead is free-wheeling through impact as if it were not attached to the shaft. If I haven't misquoted you, would that be the same for the left arm too?

Above you said "Angular momentum is not conserved in a golfer’s downswing since there is not any to be conserved to start with. It is being generated throughout the downswing by the effort expended by the golfer. Whilst being continuously generated it is redistributed due to unfolding of the club." Once the initial effort to make the club change directions in the transition is made how much effort is needed if one is relying on CF (and you can certainly shoot that down if you like . . . is that not the "ficticious" force)? So once the club is moving down how much effort is required to sustain its velocity?

Thanks!

RunRichieBucketTrickdawgCrewsdaddyPunchingBag[/quote]rundmc,

Matter and mind have in common that they are basically inert, lazy, don’t want to be disturbed. If you change people’s habit they are going to resist. If done too quickly the resistance can become quite violent.

The same with matter. It wants to be left alone, its basic nature is to be inert. If you are trying to move it around it is going to resist, more you try more it is going to resist. Matter is really very lazy.

Why matter behaves this way nobody really knows, just another of the mysteries of nature. Science is not really all that smart. It can very readily catalog things but not really explain too many things.

If you pull on a cord attached to some weight it will resist being disturbed, its basic nature being to be inert, lazy and it wants to be left alone. It is really dragging on its end of the cord and lagging behind.

The same is true if you force an object to move around some center of rotation as in a golf swing. We are continuously forcing the object not only to accelerate but also to continuously change direction.

Putting above differently we are experiencing - sensing the lag in our hands - the so called inertial reaction forces/torques.

Don’t feel embarrassed not quite understanding. The scientists who invented these concepts 3, 4 centuries ago had a very tough time themselves with the concepts of mass, force, inertia, etc..

Once the initial effort to make the club change directions in the transition is made how much effort is needed if one is relying on CF?

So once the club is moving down how much effort is required to sustain its velocity?

These two questions don’t have a clear cut answer. One can have a large startup effort and let it coast through impact. Conversely one can start very gently and step on the throttle through impact.

Centrifugal force is not a primary driving force. It is a inertial reaction force. It is acting primarily on the clubhead trying to move it as far possible away from the swing center.

Centrifugal force is equally present in both hitting and swinging. However a swinger, with relaxed hands/wrist/arms allows centrifugal force to run the show.

Lag is mainly felt at the transition since there is the maximum inertia the overcome due to a reversal of direction. Close to impact it is much more difficult to sense lag due to speed.

 

[mrodock]

The same with matter. It wants to be left alone, its basic nature is to be inert. If you are trying to move it around it is going to resist, more you try more it is going to resist. Matter is really very lazy.

Why matter behaves this way nobody really knows, just another of the mysteries of nature. Science is not really all that smart. It can very readily catalog things but not really explain too many things.

If you pull on a cord attached to some weight it will resist being disturbed, its basic nature being to be inert, lazy and it wants to be left alone. It is really dragging on its end of the cord and lagging behind.

Isn't the fact that the matter is resistant simply because of gravity. If you put a rope around a rock tightly and then pull on it (rope parallel to the ground) then the rock will resist action because it's force is being pushed downward (gravity). However, if the rock were on the edge of a ledge and you pulled it off that ledge that rock would not be resisting for long, it would be freefalling in short order. So this perceived laziness of matter is simply a matter of conditions. No?

Matt

 

[Biffer]

Sounds good to me Matt.

 

[mrodock]

Sounds good to me Matt.

I'm a "social scientist" whatever the heck that means, so I'm slow to get into such discussions and not so certain of myself.

 

[rundmc]

rundmc,


These two questions don’t have a clear cut answer. One can have a large startup effort and let it coast through impact. Conversely one can start very gently and step on the throttle through impact.

Centrifugal force is not a primary driving force. It is a inertial reaction force. It is acting primarily on the clubhead trying to move it as far possible away from the swing center.

Centrifugal force is equally present in both hitting and swinging. However a swinger, with relaxed hands/wrist/arms allows centrifugal force to run the show.

Lag is mainly felt at the transition since there is the maximum inertia the overcome due to a reversal of direction. Close to impact it is much more difficult to sense lag due to speed.

It is Swinging that is of particular interest to me so I took the liberty of bolding the statement in your post. The lazy stuff was good . . . I'm familair with lazy. Homer Kelley said that the Swinger used pivot thrust to over come the initial inertia of the club going back during the change of direction . . . he said then all the player should do was to "stay ahead of it." Any attempt to continue to accelerate was in vain because the maximum hand speed was reached early on.

Do you think that is a valid way to "swing" the club?

 

[mandrin]

Inertial and gravitational mass

Isn't the fact that the matter is resistant simply because of gravity. If you put a rope around a rock tightly and then pull on it (rope parallel to the ground) then the rock will resist action because it's force is being pushed downward (gravity). However, if the rock were on the edge of a ledge and you pulled it off that ledge that rock would not be resisting for long, it would be freefalling in short order. So this perceived laziness of matter is simply a matter of conditions. No?

Matt

mrodock,

Take an object in free space. It will have an inertial mass. Gravity does not play any role. The same situation when pushing on an object along a frictionless surface.

The effort to hold up the same object on earth is equal to the gravitational attraction. Here we have the gravitational mass. Inertia plays no role.

In short, your idea is not scientifically correct.

It is Newton who worked on this and came up with what is known as the ‘proportionality of gravitational and inertial mass’, they are equivalent.

 

[mrodock]

mrodock,

Take an object in free space. It will have an inertial mass. Gravity does not play any role. The same situation when pushing on an object along a frictionless surface.

The effort to hold up the same object on earth is equal to the gravitational attraction. Here we have the gravitational mass. Inertia plays no role.

In short, your idea is not scientifically correct.

It is Newton who worked on this and came up with what is known as the ‘proportionality of gravitational and inertial mass’, they are equivalent.

Cool Mandrin, appreciate the explanation.

 

[mandrin]

contradiction

Homer Kelley said that the Swinger used pivot thrust to over come the initial inertia of the club going back during the change of direction . . . he said then all the player should do was to "stay ahead of it." Any attempt to continue to accelerate was in vain because the maximum hand speed was reached early on.

rundmc.

There is seemingly a serious contradiction implicit in HK’s idea above.

If you don’t continue to accelerate than it is impossible to sense lag with the pressure points.

Lag is only possible by a continuous acceleration, as soon as there is constant velocity, lag disappears.

Lag is caused by a thrust, applying a force to change either the rest position or the velocity of an object.

This necessarily implies acceleration.

 

[Martee]

rundmc.

There is seemingly a serious contradiction implicit in HK’s idea above.

If you don’t continue to accelerate than it is impossible to sense lag with the pressure points.

Lag is only possible by a continuous acceleration, as soon as there is constant velocity, lag disappears.

Lag is caused by a thrust, applying a force to change either the rest position or the velocity of an object.

This necessarily implies acceleration.

Are we focused on 'hand speed' to assume constant speed? If in a pivot where the further from the center we move with components, would not the hands that are moving a given rate, not be increased by the component closer to the center as they move? Probably not clear but say the hands by themselves can only move X speed. But the effective speed when taking into account the arms, shoulders, hips, etc, will be greater.

I read Kelley's words to say don't try and accelerate with the hands, a theme he keep repeating about where to focus efforts.

I may be out to lunch on this one..

 

[Jim Kobylinski]

rundmc.

There is seemingly a serious contradiction implicit in HK’s idea above.

If you don’t continue to accelerate than it is impossible to sense lag with the pressure points.

Lag is only possible by a continuous acceleration, as soon as there is constant velocity, lag disappears.

Lag is caused by a thrust, applying a force to change either the rest position or the velocity of an object.

This necessarily implies acceleration.

Is this in relation to the force on your body in a car that is accelerating? Go 50mph on the highway and hold it constant and you are free to move around, however hammer it and downshift the car all of sudden you're stuck in your seat ACCERLATING?

thanks

 

[mandrin]

Is this in relation to the force on your body in a car that is accelerating? Go 50mph on the highway and hold it constant and you are free to move around, however hammer it and downshift the car all of sudden you're stuck in your seat ACCERLATING?

thanks

Jim,

Yes, that is correct.

Inertial forces arise with acceleration. However, no thrust, no acceleration.

Sensing lag equals sensing inertial force/torque, hence acceleration.

 

[Mick Stup]

rundmc.

There is seemingly a serious contradiction implicit in HK’s idea above.

If you don’t continue to accelerate than it is impossible to sense lag with the pressure points.

Lag is only possible by a continuous acceleration, as soon as there is constant velocity, lag disappears.

Lag is caused by a thrust, applying a force to change either the rest position or the velocity of an object.

This necessarily implies acceleration.

Mandrin

Just a thought, but could it be possible that, in the absence of continuous acceleration, we might have constant velocity but since it is angular velocity we can still have (and feel) inertia / lag due to the constantly changing direction?

Great thread BTW

 

[rundmc]

rundmc.

There is seemingly a serious contradiction implicit in HK’s idea above.

If you don’t continue to accelerate than it is impossible to sense lag with the pressure points.

Lag is only possible by a continuous acceleration, as soon as there is constant velocity, lag disappears.

Lag is caused by a thrust, applying a force to change either the rest position or the velocity of an object.

This necessarily implies acceleration.

This makes sense . . . and I am certainly not qualified to postulate on this stuff. What about this . . . The hands lose their speed before the club I think? So would the clubhead be still accelerating even though the hands aren't? According to Homer Kelley the Pressure Points in the hands are Clubhead Feel (sweet spot) . . . so if we are to accept that premise (which maybe we shouldn't) would lag not still be present?

Actually I think the post by Martee is more along the lines of what I was trying to ask . . .

Anyway thanks for fielding these questions. Holla!

 

[mandrin]

Mandrin

Just a thought, but could it be possible that, in the absence of continuous acceleration, we might have constant velocity but since it is angular velocity we can still have (and feel) inertia / lag due to the constantly changing direction?

Great thread BTW

Mick,

Let’s consider your suggestion that with constant angular velocity we possibly can still have (and feel) inertia / lag due to the constantly changing direction?

First the clubhead wants to move inwards towards the center of rotation. Then, subsequently, when picking up some speed, centrifugal force starts throwing the clubhead outwards.

Consequently, since considering constant speed for the arms, the pressure points on the hands change then form positive to negative during the downswing.

 

[mandrin]

Are we focused on 'hand speed' to assume constant speed? If in a pivot where the further from the center we move with components, would not the hands that are moving a given rate, not be increased by the component closer to the center as they move? Probably not clear but say the hands by themselves can only move X speed. But the effective speed when taking into account the arms, shoulders, hips, etc, will be greater.

I read Kelley's words to say don't try and accelerate with the hands, a theme he keep repeating about where to focus efforts.

I may be out to lunch on this one..

Martee, I am not focused on anything in particular just reacting to post # 44 and pointing out that if there is no effort to accelerate that there is a problem with the concept of pressure points in the downswing.

I like to remind that HK is likely mentioning things form a perspective of feel, not having done any measurements or calculations. We all know that feel and real are, for a golfer, not always in agreement.

One can not accelerate the hands by themselves. Only by a torque form the inner core, a shoulder torque or a by thrust re to the trail shoulder due to torque at trail elbow. However it is indeed perfectly normal to feel as if the hands act by themselves.

Hence we have to be careful not to mix feel and real. Even simply dealing only with the real of a swing it is already very complex.

 

[Martee]

...

I like to remind that HK is likely mentioning things form a perspective of feel, not having done any measurements or calculations. We all know that feel and real are, for a golfer, not always in agreement.

.....

Hence we have to be careful not to mix feel and real. Even simply dealing only with the real of a swing it is already very complex.

That IMO the bolded is an understatement...