It has obviously gotten to you - at least my attack (if it was an attack) was towards an arguement and therefore indirect... Yours wasn't...:naughty:

Well actually you quoted Homer Kelley and i'm explaining a part of it....just you don't realise it...

How many times do I have to answer the same question....

Which would be clearer to you if you spend enough time to read and understand the language of the book.

It is up to those who wish to disprove any theory to do so...

Homer Kelley is unfortunately not with us anymore which means that he is no longer around to be in a position to talk on such matters.

Nice post Mike.

You've got a good handle on things from my point of view, but by looking at the system as a whole (like yoda did with the string) it leaves greater scope for misunderstanding and it is harder to identify where the misunderstanding lies.

There is a nice student exercise that beginning physics students use about a man standing on bathroom scales whilst a lift accelerates upward. I'll run through it if anybody thinks it will help, but to go back to your examples...

If you push on your car the equal and opposite reaction is that the car pushes on you with the same force and in the opposite direction. You push on the earth and the earth pushes back, but this pair of equal and opposite forces will be different in magnitude to the push on car/car pushes back. The second phase of analysis is to look at each object and ask what forces are acting. On the car, your push. On you, the car's push and the ground's push. On the ground, your push.

With the rock and the string, if the mass of the string is important then we can't perform a correct analysis without separating considering the "string on rock/rock on string" and "boy on string/string on boy" pairs separately because they will have different magnitudes. We can't just say "boy on rock/rock on boy" without things getting very muddled.

This is where the man on scales in lift will help if you need more detail.

I'm not familiar with the term "equilbrants", but action/reaction pairs are always equal and opposite, and it is helpful to identify the action/reaction pairs before considering resultant forces on each object.

I would consider equilibrium (taking a guess at your meaning) to apply to an individual object within a system, or to the system as a whole. Action/reaction is a different concept to equilibrium.

Excellent, we've got to the core of the issue very quickly.
When we speak of the rock's point of view, we are talking (I hope) about what you would see through a tiny camera attached to the rock. Through this camera we would see such interesting sights as a stationary rock (because we are attached to it), the centre of motion (the boy's hand) would be stationary, and everything else in the world would appear to be in the process of being flung from away from the centre of motion. The centrifugal force (away from the centre) will neatly balance the centripetal force (toward the centre), but no net force is acting on the rock. It is not being flung out. It just sits there stationary in the camera shot.

The problem is that this is not a helpful frame of reference because it is not an inertial frame of reference. We have to do all sorts of fudging if we are to explain why all of the objects (grass, trees, etc) are being flung away from the centre.

If we want to apply the usual laws of physics we need to look from an intertial frame of reference. The string pulls in on the rock (centripetal). The string pulls out on the man (centrifugal). The force on the rock is not balanced, and the centrifugal force only affects the string and the boy.

Nice post drewitgolf.

I have no problem with Mr Kelley's use of the word "centrifugal force" in a loose sense. The dictionary definition has the same problem as yoda's explanation. If you look at other technical terms defined in dictionaries, you'll often say to yourself that they haven't got it quite right.

The explanation of what causes the throw out effect is quite complex for such a simple phenomenon. I could understand it if Mr Kelley decided to call it "centrifugal force". The problem is that it then sows the seeds for all sorts of bogus physics when people take the words at face value.

Spot on annekin!

"While Centrepetal force pulls it in a circle...Centrifugal force changes the length of this string..."

Centripetal force acts on the rock. Centrifugal force acts on the string. For other contributors, remember that these words aren't magic. Centrifugal=away from the centre. Centripetal=toward the centre.

Nope. I've read some of your other posts. You've got some really good ideas, and your ideas seem well received here. Good luck with them.

I'd be delighted if you choose to follow yoda's lead in this thread and continue to discuss the topic. I'm only interested in the physics underlying TGM though. I'm happy to let others judge your words to me. That's about all I have to say to you really.

:oops:
Sorry about that. My mistake. I am in well over my depth here but I am trying to understand what you are getting at.
Do the image and definitions have any bearing on this topic?

Resultant - the single force that is equal to 2 or more forces.

Equilibrant - the single force that will balance 2 or more forces. Equal in magnitude but opposite in direction of the resultant.

Thats fine ....

Still waiting to see where Homer has said it is centrifugally powered....

Yes. In terms of your diagram the main idea I'd like to add is that in general the three forces are all acting on the same body, but will come from different action/reaction pairs.