Re: The SR between reality and appearance

wugi il 10/04/2024 07:16:40 ha scritto:

Here is the drawing:
https://www.geogebra.org/m/tecb3dkw
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For me, only the two blue and red forces act between man and the carousel; and nothing else.
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For you?

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So you've despatched the blue force to nowhere ;-)
It is not generated where you draw it, that's a transmitted reaction force (through the carousel's structure). It's generated in the foundation/anchor point(s, or areas, or volumes) of the carousel. After the red action force has been transmitted to those in the first place, of course.
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If you consider initially only the red centrifugal force, and no foundations, then the carousel will tend to be accelerated along the (moving) centrifugal force, for lack of any basis for generating a reaction force.
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So then, you have to count at least with Earth. Whether also with the rest of the Universe, that's a problem that even Mach couldn't solve in Principle, AFAIU.

I have despatched the blue force to the center of rotation O and it is the force that the carousel exerts on the man's feet.

In fact, if there were no blue centripetal force, the man's feet would go straight forward, sliding without rotating.

It is the constraint at point P that prevents slipping and forces the foot to follow the rotation of the carousel.

Obviously, the foot reacts to this blue centripetal push from the carousel with its own red centrifugal force on the carousel: note that the man must be inclined to push and not to fall.

The forces that act at the contact point P are these that I mentioned and what happens beyond and on this side of the point P can only increase or decrease both contact forces, without altering their equality.

Luigi Fortunati