The magic of science

[mandrin]

Centripetal acceleration of the 1ball or centrifugal force of the 1ball depending on the frame of reference.

Centripetal acceleration (centrifugal force) increases as 1ball velocity increases and radius of rotation decreases. The interesting part of it to me is how this combination works rapidly accelerating as it is able to draw kinetic energy from 3ball.

I must admit that centrifugal force may be more understandable to most people (making more common sense) than thinking in terms of centripetal acceleration.

What comes to googling, I also admit that have to resort to it sometimes, since I do not yet know everything. And I might even sometimes change my opinion when I learn something new.

Anyway I'm still on the opinion that use of centrifugal force is not necessary in physics, but I will not object to the use of it anymore.

Let's put aside the convenient mumbo jumbo about reference frames and simply decide to use a simple Newtonian inertial reference frame, i.e., mother earth.

Having cleared up the matter of reference frames let me ask you again what is the nature of the force acting through the cord on the 3ball mass?

Let me just help you a bit - centripetal stands for ‘center seeking’ and centrifugal means ‘center fleeing‘.

I also like to remind you that you have previously allowed graciously Newton’s third law to be valid but seemingly seem to deny it again.

In addition, we are not discussing all of physics but a very simple and precisely defined elegant experiment, so again what is your answer re to my question.

 

[jake2]

Let's put aside the convenient mumbo jumbo about reference frames and simply decide to use a simple Newtonian inertial reference frame, i.e., mother earth.

Having cleared up the matter of reference frames let me ask you again what is the nature of the force acting through the cord on the 3ball mass?

Let me just help you a bit - centripetal stands for ‘center seeking’ and centrifugal means ‘center fleeing‘.

I also like to remind you that you have previously allowed graciously Newton’s third law to be valid but seemingly seem to deny it again.

In addition, we are not discussing all of physics but a very simple and precisely defined elegant experiment, so again what is your answer re to my question.

Sorry Mandrin, but the way I understand an inertial reference frame is that you do not need/use centrifugal force in the equations. Mother earth's surface especially is non-inertial. Because we are rotating with earth, it is possible to observe forces caused by the rotation, so those forces are real to us.

I might have to do more googling to understand the difference between what you mean specifically by Newtonian inertial reference frame and how I understand inertial reference frames.

From golf swing point of view, I just like to think that I'm the one pulling the club, causing tangential and centripetal acceleration, instead of thinking that I'm doing something to make the club pull me. But that's my personal preference.

 

[mandrin]

Sorry Mandrin, but the way I understand an inertial reference frame is that you do not need/use centrifugal force in the equations. Mother earth's surface especially is non-inertial. Because we are rotating with earth, it is possible to observe forces caused by the rotation, so those forces are real to us.

I might have to do more googling to understand the difference between what you mean specifically by Newtonian inertial reference frame and how I understand inertial reference frames.

From golf swing point of view, I just like to think that I'm the one pulling the club, causing tangential and centripetal acceleration, instead of thinking that I'm doing something to make the club pull me. But that's my personal preference.

jake2, you keep dancing around, dodging the issue, without addressing my simple basic question. Your diversion about inertial frames is in that respect rather comical and clearly demonstrating that you are dancing superficially on the surface, knowing very little about it - gleaning little bits of science and knowledge here and there as needed, Googling around. However, you are very representative of many doing exactly the same. Any scientist will immediately tell you for a golf swing mother earth to be a perfect inertial reference frame. We are not discussing GPS, Einstein, black holes or interstellar phenomena, simply just a few golf balls falling under the effect of gravity. I will try it once more since I am willing to spend plenty of time but only when I feel there is some open mind at the other side. I dislike wasting my time when no hope for any rational exchange.

So let’s try it just once more. Carefully look at Fig1.
Just forget about any itchy temptation to Google.
Just sit down quietly, relax, take a deep breath, look at Fig1, and assess the situation for yourself.

What do you see?
Two masses connected by a cord restraint by a pivot.
Fine, we made some progress. Tell me next what do you see acting as forces at the end of the cord attached to the 1ball mass.
Well, acting on the 1ball mass there is gravity and the centripetal force F2 exerted by the cord on the 1ball mass.
Splendid, continue, you are doing fine.
On the end of the cord there is the centrifugal force F1 exerted by the 1ball mass on the cord.
Finally, you got it. Congratulations.

Jake2, you see it is not so difficult after all. You probably realize by now that you have applied simply Newton‘s third law - Forces always occur in equal and opposite pairs. If object A exerts a force on object B, an equal but opposite force is exerted by object B on object A.

This lasting confusion about centrifugal force is primarily due to science and the scientists themselves. Expressions such as inertial force and centrifugal force have been defined and used in ambiguous ways. However it remains always rather funny to see scientists and laymen alike, almost in one phrase, both admitting the existence of centrifugal force and yet also immediately denying it to be real. Well you can’t have it both ways. It is or it is not.

 

[jake2]

jake2, you keep dancing around, dodging the issue, without addressing my simple basic question. Your diversion about inertial frames is in that respect rather comical and clearly demonstrating that you are dancing superficially on the surface, knowing very little about it - gleaning little bits of science and knowledge here and there as needed, Googling around. However, you are very representative of many doing exactly the same. Any scientist will immediately tell you for a golf swing mother earth to be a perfect inertial reference frame. We are not discussing GPS, Einstein, black holes or interstellar phenomena, simply just a few golf balls falling under the effect of gravity. I will try it once more since I am willing to spend plenty of time but only when I feel there is some open mind at the other side. I dislike wasting my time when no hope for any rational exchange.

So let’s try it just once more. Carefully look at Fig1.
Just forget about any itchy temptation to Google.
Just sit down quietly, relax, take a deep breath, look at Fig1, and assess the situation for yourself.

What do you see?
Two masses connected by a cord restraint by a pivot.
Fine, we made some progress. Tell me next what do you see acting as forces at the end of the cord attached to the 1ball mass.
Well, acting on the 1ball mass there is gravity and the centripetal force F2 exerted by the cord on the 1ball mass.
Splendid, continue, you are doing fine.
On the end of the cord there is the centrifugal force F1 exerted by the 1ball mass on the cord.
Finally, you got it. Congratulations.

Jake2, you see it is not so difficult after all. You probably realize by now that you have applied simply Newton‘s third law - Forces always occur in equal and opposite pairs. If object A exerts a force on object B, an equal but opposite force is exerted by object B on object A.

This lasting confusion about centrifugal force is primarily due to science and the scientists themselves. Expressions such as inertial force and centrifugal force have been defined and used in ambiguous ways. However it remains always rather funny to see scientists and laymen alike, almost in one phrase, both admitting the existence of centrifugal force and yet also immediately denying it to be real. Well you can’t have it both ways. It is or it is not.

You do not need two forces to solve simple straight line acceleration (F=ma), even if the opposing force is present when you observe from the moving frame. Why do you have to use centrifugal force when you can use centripetal acceleration to solve the problem?

Pulling a mass on a string:
In a straight line motion I see pulling force as the action causing acceleration and the opposing force as a reaction. Same applies in my mind to to circular motion where I see centripetal pull as the action causing the curved path and centrifugal force as the reaction. You use one or the other in the equations describing the motion, not both at the same time.
Am I wrong in your opinion here?

Or is this more of a philosophical question?
I must admit that calling the forces caused by acceleration or rotation fictitious or pseudo forces makes it confusing, like they did not exist, even when you can observe them.

Anyway, you are right that I'm not an expert in the subject. If you think that most of the scientists are wrong on this, then you should take it up with them and not me.

 

[Brian Manzella]

Another really good Mandrin thread, ruined by science Kool_aiders....

 

[mandrin]

You do not need two forces to solve simple straight line acceleration (F=ma), even if the opposing force is present when you observe from the moving frame. Why do you have to use centrifugal force when you can use centripetal acceleration to solve the problem?

Pulling a mass on a string:
In a straight line motion I see pulling force as the action causing acceleration and the opposing force as a reaction. Same applies in my mind to to circular motion where I see centripetal pull as the action causing the curved path and centrifugal force as the reaction. You use one or the other in the equations describing the motion, not both at the same time.
Am I wrong in your opinion here?

Or is this more of a philosophical question?
I must admit that calling the forces caused by acceleration or rotation fictitious or pseudo forces makes it confusing, like they did not exist, even when you can observe them.

Anyway, you are right that I'm not an expert in the subject. If you think that most of the scientists are wrong on this, then you should take it up with them and not me.

jake2,

Our magician’s trick probably forces you to think a bit outside the box so that is likely why you are lost and hence continuously don’t respond to my simple basic question. You are every time taking another tangent but I will continuously and patiently bring you back to our issue at hand.

You seem to know about Newton’s famous second law but equally not be familiar, like so many people, with the implications of his third law about action and reaction. It would be helpful if you are a bit familiar with free body diagrams but we will do without.

You hang your arguments this time onto one body. However, in our simple experiment there are two bodies, interacting. Very different situation. Hope you agree. Action on one body generates a reaction, which in turn becomes action for the second body and vice versa.

So again look at Fig1, forget all the many web sites ‘badmouthing’ centrifugal force and just think a bit for your self.

- The centrifugal reaction F1, associated with the 1ball mass, becomes action for the 3ball mass, in addition to gravity.

- A force with you can measure does exist. Hopefully you agree. If not, I give up.

- The centrifugal force F1 is readily measured noting the deflection in the spring of a tension scale, subtracting deflection due to gravity.

- Inevitable conclusion - centrifugal force, in our experiment, exists as a real action force, and is not some strange hocus pocus fictitious entity as so many are insisting it to be.

 

[jake2]

jake2,
You seem to know about Newton’s famous second law but equally not be familiar, like so many people, with the implications of his third law about action and reaction. It would be helpful if you are a bit familiar with free body diagrams but we will do without.

You hang your arguments this time onto one body. However, in our simple experiment there are two bodies, interacting. Very different situation. Hope you agree. Action on one body generates a reaction, which in turn becomes action for the second body and vice versa.

So again look at Fig1, forget all the many web sites ‘badmouthing’ centrifugal force and just think a bit for your self.

- The centrifugal reaction F1, associated with the 1ball mass, becomes action for the 3ball mass, in addition to gravity.

This is getting more interesting.

How do you define which is action and which is reaction in a two-body system, because they both appear to be acting and reacting at the same time? [EDIT] I think I got it. Action-Reaction Pair.

And what I would find REALLY interesting, if you could please enlighten us a bit more, how this applies to a golf swing? You mentioned that decreasing radius of rotation is one way of looking at it besides kinetic chain. Is a combination possible?

- A force with you can measure does exist. Hopefully you agree. If not, I give up.

I totally agree that in can be measured (I said observed). That's why I said the term fictitious force, that you see being used to classify it, is confusing.

 

[jake2]

Another really good Mandrin thread, ruined by science Kool_aiders....

Sorry Brian, things got carried away.

 

[mandrin]

You mentioned that decreasing radius of rotation is one way of looking at it besides kinetic chain. Is a combination possible?

Every golfer is by definition a kinetic chain, being a linked ensemble of various masses.
Hence there is no choice of being one or not.
The choice however is in optimizing its action.
Shortening the swing radius is hence always part of the kinetic chain.

Shortening the swing radius is a subject by itself and will post about it when ready to do so.
All my posts take lots of time there being no easy and convenient copy/paste operations.

However in the mean time have a look at an old post of mine - Golf swing and playground swing.

 

[mandrin]

Magician’s intuition - true or false?

 

[JonWil]

I believe the 100 ball mass will be stopped. Explain it to the rest of the folks for me would you Mandrin.

 

[mandrin]

I believe the 100 ball mass will be stopped. Explain it to the rest of the folks for me would you Mandrin.

JonWil,

Personally, I would not have put a penny on the 1ball mass being able to stop the 100ball mass in time, so I am curious to hear your reasons why you came to such a surprising conclusion.

 

[mandrin]

Magician’s intuition - true or false?

It seems from the ‘avalanche’ of reactions that I am close to reaching dangerously the limit of intellectual curiosity of this forum. Yet magic normally attracts young and old everywhere, universally. This forum is increasingly sound asleep.

 

[starretj]

It seems from the ‘avalanche’ of reactions that I am close to reaching dangerously the limit of intellectual curiosity of this forum. Yet magic normally attracts young and old everywhere, universally. This forum is increasingly sound asleep.

mandrin, funny you posted this. I worked for a couple of hours on this problem this morning until my head hurt.

The best I could do was get to the point where if the single ball could overcome the force of the 100 balls, it's velocity would have to be equal or greater than 10 times the square root of the radius of curvature. Of coarse this applies at the bottom of it's swing arc so I don't even know if it would get there. My guess is that the 100 ball mass would be too much, but the question wouldn't be interesting if the logical were true.

I was hoping to get to the point of analyzing a relationship between the two masses and if there is a point when the large mass overcomes the change in the radius of curvature. I couldn't get there.

Am I on the right track? Any help would be appreciated.

 

[mandrin]

Only one light is needed to chase the darkness.

mandrin, funny you posted this. I worked for a couple of hours on this problem this morning until my head hurt.

The best I could do was get to the point where if the single ball could overcome the force of the 100 balls, it's velocity would have to be equal or greater than 10 times the square root of the radius of curvature. Of coarse this applies at the bottom of it's swing arc so I don't even know if it would get there. My guess is that the 100 ball mass would be too much, but the question wouldn't be interesting if the logical were true.

I was hoping to get to the point of analyzing a relationship between the two masses and if there is a point when the large mass overcomes the change in the radius of curvature. I couldn't get there.

Am I on the right track? Any help would be appreciated.

starretj,

Thanks for your comments. Hope you did not get a headache.

Could you tell me what you mean by ‘the velocity would have to be equal or greater than 10 times the square root of the radius of curvature’?

I feel that most would agree that it is not reasonable at all to expect the 1ball mass to be able to stop the big 100 ball mass once it is falling down vigorously. But that is precisely why it is eminently suitable as a magician’s trick.

To be able to stop the big mass one could speculate perhaps on various possible avenues.

For instance, the 1ball mass quickly somehow attains such a velocity that its associated centrifugal force is capable of decelerating and subsequently stopping the falling 100 ball mass in a short time interval. This implies that the dynamic force required to do so has to be substantial larger than the gravity force of 100 mg acting on the big mass. If completely arbitrarily we guess it to be 10 times, than this implies that the small mass has to develop a centrifugal force over 1000 times its own weight. It could be even substantially more.

Another avenue would be that the 1ball mass somehow attains quickly a very large angular velocity and quickly wraps around the pivot and smothering the motion of the big 100ball mass primarily by the ensuing friction force. Perhaps a combo of both avenues.

starretj, before long I will put up an exact solution but it is always interesting, in the mean time, to get some feedback from the more curious people like yourself, interested in the how and why of things, not particularly from those sound asleep on this forum, just hanging around for that one magic tip which will hopefully improve drastically their failing golf swing.

 

[starretj]

starretj,

Thanks for your comments. Hope you did not get a headache.

Could you tell me what you mean by ‘the velocity would have to be equal or greater than 10 times the square root of the radius of curvature’?

mandrin, the only place I could get to where I felt like I had an idea of working on this problem was to draw a free body diagram and analyze when both ball masses are hanging straight down. For the centrifugal force to be enough to overcome the 100 ball mass, then the force would have to be equal to the 100 ball mass(plus a little). If I can remember correctly, the 1 ball mass would create a force equal to: mass X ((velocity ^2/ radius of curvature)). Solving for velocity, it would have to be equal to 10 times the sq. rt of the radius of curvature.

Probably not right and maybe not even close. If my thinking is right up to this point, then the diminishing radius helps keep the velocity needed rather low especially considering that you take the square root of it.

p.s. After my headache this morning, this had better lead to a quick fix for my swing!

 

[JonWil]

JonWil,

Personally, I would not have put a penny on the 1ball mass being able to stop the 100ball mass in time, so I am curious to hear your reasons why you came to such a surprising conclusion.

Mandrin,
Genius in the 'right brain' - with full deference to yours in 'the left.'

 

[mandrin]

mandrin, the only place I could get to where I felt like I had an idea of working on this problem was to draw a free body diagram and analyze when both ball masses are hanging straight down. For the centrifugal force to be enough to overcome the 100 ball mass, then the force would have to be equal to the 100 ball mass(plus a little). If I can remember correctly, the 1 ball mass would create a force equal to: mass X ((velocity ^2/ radius of curvature)). Solving for velocity, it would have to be equal to 10 times the sq. rt of the radius of curvature.

Probably not right and maybe not even close. If my thinking is right up to this point, then the diminishing radius helps keep the velocity needed rather low especially considering that you take the square root of it.

p.s. After my headache this morning, this had better lead to a quick fix for my swing!

starretj,

Good start but consider the following. It needs time to develop velocity for the 1ball mass which indeed reaches a maximum at the bottom. Therefore there is very little time left to decelerate and stop the 100ball mass. Just intuitively you can imagine that the required dynamic force has to be therefore substantial greater than the static weight of the 100 ball mass. You probably start getting a bit suspicious that there is perhaps some secret interaction between those two masses to befuddle the curious mind wanting to know.

 

[mandrin]

Mandrin,
Genius in the 'right brain' - with full deference to yours in 'the left.'

JonWil,

Nice to let me know. Next time I am really stuck with an analytical problem I will submit it to your intuitive prowess.

 

[Jon Hardesty]

Could it be something to do with the shortening of the cord attached to the one ball mass as the 100 ball mass pulls on it? Thus, creating a shortening of the radius on the one ball cord and increasing it's angular velocity, as well as wrapping around the pivot point?