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Re: [Phys-l] Centrifugal redux




----- Original Message ----- From: "Ken Fox" <physicsfox23@gmail.com>

As for agents of a force, how imaginary is gravity?

In the Newtonian World the agents are the masses. The earth pulls down on the ball, the ball pulls up on the earth. All the Newtonian forces are interactions between two things--which, IMO, is the one idea you have on which to hang the Third Law--to try and understand it rather than just memorize the mantra. It is, again IMO, easier to 'see' this in the gravitational case where mass A attracts mass B and mass B attracts mass A with no particular 'predominance' given to one or the other. Harder to 'see' that when I push on the wall, the wall pushes back on me.


Let's hear it for the Principle of Equivalence and a possible extension to
Centrifugal Fields. I notice such every time in the winter when I turn left
and feel hot air come my way. High school students can easily grasp such
ideas.

That's fine as long as they can keep straight when the Newtonian principles apply and when they don't (or give up on Newton entirely). ;-)

Rick