Was Homer Wrong?

[golf_sceptic]

now that we all understand the differences between CF & CP...which does not change the fact that there are forces acting...just definitions to clarify

Got it in one! But the next time somebody claims centrifugal
force powers anything you'll know what to say. It doesn't!

The endless belt...

I refer here only to a little video that seems to pop up regularly.
It shows a model held in somebody's hand with
the handle being turned and a series of little golf clubs
moving along a straight section (of belt) and then around
a curved section (of belt). The commentator points out how
the little clubs whiz around the curved part.

Now that's fine as far as it goes. Unfortunately that is also
as far as the model validly goes. The little clubs do whiz
around the end. Unfortunately the model does not show how the
clubhead accelerates, or that CF throws the club out or anything
else as is frequently claimed.

For reference, here is what happens in the model.
Firstly, for simplicity we assume that the handle is
being turned at a constant rate. This in turn means
that all parts of the belt are moving at a constant
speed and so are the grip ends of all the little clubs.

This has three results.
1. The clubheads are moving at a constant speed whilst
the belt is on the flat.
2. The clubheads are moving at a higher but constant
speed whilst the belt is on the curve.
3. The change in speed from lower to higher happens
instantaneously (not gradually) when the belt changes
shape from straight to curved.

When the little club moves from the straight part to
the curved part there will be quite a jolt to the little
club and you would not want to try this in real life.
It would be a bit like going over the pulleys when riding
on a chairlift in the snow. In the model this is disguised
by the general jerkiness involved in winding the handle
whilst the model is held in the hand.

As for my tone on arrival here, have a look at what you
were saying in this thread prior to my contribution especially
the "centrifugally powered golf swing" snideness and the
person who decided to visit ISG to "tell us off", followed
after my post by the mockery about the "force with no name".

I make a contribution and get a straw man argument
from one of the most knowledgeable teachers on the planet.

It cuts both ways fellas. Fair's fair!

[annikan skywalker]

What is the name of the Force with no name?..no mockery...label it please.. we would like to learn for we are just humble peasants ..no need to be defensive..just name the force that is opposite of Centrepetal Force....or isn't there a force...I would agree that the force that pulls the string in an angular motion IS Centrepetal Force..then what force pulls the string outward or lengthwise?..or is this just an accident?....What makes the radius of gyration move from smaller to larger?.... We just would like to know without the TGM spin on it!!!

[golf_sceptic]

The words centripetal and centrifugal in physics have their dictionary meanings. centripetal=toward the centre, centrifugal=away from the centre. They are equal and opposite, action and reaction.

Most people get it wrong because they do not understand that the centripetal force acts on the stone, and the centrifugal force acts on the string (or the boy). We then get incorrect statements about the centrifugal force throwing the rock out and keeping the string taut and that sort of thing.

What keeps the string taut? The boy pulling on it.
What balances the centripetal force on the stone? Nothing, that's why it moves in a circle.

As a general rule, the more words used to describe the phenomenon,
the more errors will be introduced.

[Daryl]

The words centripetal and centrifugal in physics have their dictionary meanings. centripetal=toward the centre, centrifugal=away from the centre. They are equal and opposite, action and reaction.

Most people get it wrong because they do not understand that the centripetal force acts on the stone, and the centrifugal force acts on the string (or the boy). We then get incorrect statements about the centrifugal force throwing the rock out and keeping the string taut and that sort of thing.

What keeps the string taut? The boy pulling on it.
What balances the centripetal force on the stone? Nothing, that's why it moves in a circle.

As a general rule, the more words used to describe the phenomenon,
the more errors will be introduced.

Regardless of terminology, I have seen Golfers swing a clubhead attached to a 48" rope. They swing this rope club and hit the ball. The ball goes far. Longer than I am with a graphite shaft. Whatever name you use to identify the forces involved, we know that very great forces were involved, more than muscle power can generate. And it makes your list of power sources look a little inapplicable.

Sources of power in the golf swing (focussed on the club)
1. early in the downswing -- leverage through "locked" wrists
2. mid-downswing to impact -- the slingshot (or flail) effect
together with leverage applied through the hands.

[golf_sceptic]

Regardless of terminology, I have seen Golfers swing a clubhead attached to a 48" rope. They swing this rope club and hit the ball. The ball goes far. Longer than I am with a graphite shaft. Whatever name you use to identify the forces involved, we know that very great forces were involved, more than muscle power can generate.

Yes. I remember Wedgy Winchester (US pro who toured Australia in the 70s
and gave trick shot demos) and his rubber hose shafted club well. There
was centrifugal force at work there as well, but not on the clubhead!

And it makes your list of power sources look a little inapplicable.

Nope. The power comes from the second of the sources -- the flail or slingshot effect. This is what Homer incorrectly labelled as centrifugal.

Let's not get distracted though. It's not my theories that are under the spotlight. It's simply the misunderstanding of centrifugal force in Homer's writings (and most explanations) that is at stake. That's all. No more. No less. I'm more than happy to explain the physics correctly and let others ponder on the implications for TGM. In my book it doesn't change the teaching principles one little bit.

[ThinkingPlus]

The words centripetal and centrifugal in physics have their dictionary meanings. centripetal=toward the centre, centrifugal=away from the centre. They are equal and opposite, action and reaction.

Most people get it wrong because they do not understand that the centripetal force acts on the stone, and the centrifugal force acts on the string (or the boy). We then get incorrect statements about the centrifugal force throwing the rock out and keeping the string taut and that sort of thing.

What keeps the string taut? The boy pulling on it.
What balances the centripetal force on the stone? Nothing, that's why it moves in a circle.

As a general rule, the more words used to describe the phenomenon,
the more errors will be introduced.

Centrifugal force is a convenient term describing an effective force present on objects in a rotating reference frame (an object undergoing centripetal acceleration). It is what our bodies, arms, and hands "feel" as the pulling away from the center of rotation during a swing. This concept and feel can be used as an aid to creating angular velocity. That is all that is claimed within TGM to my knowledge. Angular velocity and acceleration is what ultimately matters.

[golf_sceptic]

Centrifugal force is a convenient term describing an effective force present on objects in a rotating reference frame (an object undergoing centripetal acceleration).

Yes, but everything gets a whole lot harder once you start using non-inertial frames of reference. Bear in mind also that in a non-inertial frame of reference such as that viewed using a camera attached to the clubhead, the centrifugal force neatly balances the centripetal force and the clubhead remains still in the camera's eye as does the centre of the motion. Only the objects not attached to the clubhead appear to be flung outward. Again, the clubhead is not accelerated outward by centrifugal force in that or any other useful frame of reference because centrifugal force does not act on the clubhead.

The "throw out" effect is real. It is not, however, created by centrifugal force.

It is what our bodies, arms, and hands "feel" as the pulling away from the center of rotation during a swing.

Yes. 100% correct. The reaction to our pulling inward (centripetal force) is the outward (or centrifugal) force that we feel and it acts on our bodies (not on the clubhead).

This concept and feel can be used as an aid to creating angular velocity.

Nope. As you so clearly pointed out, the centrifugal force acts on us not the clubhead.

That is all that is claimed within TGM to my knowledge. Angular velocity and acceleration is what ultimately matters.

Correct. The TGM concept of centrifugal force is wrong. Angular velocity and acceleration are paramount, but that is a topic for another day!

[strav]

Don't know why but this extract keeps springing to mind.

`And only one for birthday presents, you know. There's glory for you!'
`I don't know what you mean by "glory",' Alice said.
Humpty Dumpty smiled contemptuously. `Of course you don't -- till I tell you. I meant "there's a nice knock-down argument for you!"'
`But "glory" doesn't mean "a nice knock-down argument",' Alice objected.
`When I use a word,' Humpty Dumpty said, in rather a scornful tone, `it means just what I choose it to mean -- neither more nor less.' `The question is,' said Alice, `whether you can make words mean so many different things.'
`The question is,' said Humpty Dumpty, `which is to be master -- that's all.'
Alice was too much puzzled to say anything.

[birdie_man]

I for one welcome this debate.

I don't think this guy should be made the enemy.

Would it be cool if Homer was 100% right on everything? Hell yes.

What if he isn't? TGM gonna go down in flames? Hell no.

We're talking about small things here.

It's most important to get this right....

We have to remember.....when Homer died he had not hung up his "golf researchin pants"....so let's not....

[strav]

I for one welcome this debate.

I don't think this guy should be made the enemy.

Would it be cool if Homer was 100% right on everything? Hell yes.

What if he isn't? TGM gonna go down in flames? Hell no.

We're talking about small things here.

It's most important to get this right....

We have to remember.....when Homer died he had not hung up his "golf researchin pants"....so let's not....

Hi Birdie_Man. As you started this thread and welcomed the debate, you may be one of the last objective participants. If so, for your information, here is "Centrifugal force" from a neutral, namely Encyclopedia Britannica.

"Centrifugal Force, quantity, peculiar to a particle moving on a circular path, that has the same magnitude and dimensions as the force that keeps the particle on its circular path (the centripetal force) but points in the opposite direction. A stone whirling in a horizontal plane on the end of a string tied to a post on the ground is continuously changing the direction of its velocity and, therefore, has acceleration toward the post. This force is equal to the square of its velocity divided by the length of the string According to Newton’s second law; acceleration is caused by a force, which in this case is the tension in the string. If the stone is moving at a constant speed and gravity is neglected, the inward-pointing string tension is the only force acting on the stone. If the string breaks, the stone, because of inertia, will keep on going in a straight line tangent to its previous circular path; it is not the influence of a centrifugal “force” that will make the stone fly off in a radially outward direction.

Although it is not a real force according to Newton’s laws, the centrifugal-force concept is a useful one. For example, when analyzing the behaviour of the fluid in a cream separator or a centrifuge, it is convenient to study the fluid’s behaviour relative to the rotating container rather than, relative to the Earth; and, in order that Newton’s laws be applicable in such a rotating frame of reference, an inertial force, or a fictitious force (the centrifugal force), equal and opposite to the centripetal force, must be included in the equations of motion. In a frame of reference attached to the whirling stone, the stone is at rest; to obtain a balanced force system, the outward-acting centrifugal force must be included.

Centrifugal force can be increased by increasing either (1) the speed of rotation, (2) the mass of the body, or (3) the radius, the distance of the body from the centre of the curve. Increasing either the mass or the radius increases the centrifugal force proportionally, but increasing the speed of rotation increases it in proportion to the square of the speed; that is, an increase in speed of 10 times, say from 10 to 100 revolutions per minute, increases the centrifugal force by a factor of 100. Centrifugal force is expressed as a multiple of g, the symbol for normal gravitational force (strictly speaking, the acceleration due to gravity). Centrifugal fields of more than 1,000,000,000 g have been produced in the laboratory. "