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Tina wrote:
physicsI am currently teaching forces to my general
class.
John Barrer wrote:
Start by getting them used to the question "What
objects are interacting with the mass?"
If that means what I think it means, then I'm not
convinced that's the right starting point.
I don't subscribe to the school of thought that
starts
with position -> velocity -> acceleration and then
_defines_ force in terms of F=ma. (If force is
defined
that way then F=ma becomes a tautology.)
Instead, I take the point of view (both for physics
reasons and pedagogical reasons) that force exists
unto itself. (Therefore F=ma is a nontrivial
expression, subject to experimental verification
or falsification.)
Specifically, I would hand the student one end of a
rope. I pull on the other end and say
"Feel that? That's a force."
I pull harder and say
"Feel that? That's a larger magnitude of
force."
I pull off to the side and say
"Feel that? That's a force in a different
direction."
You will note that these exemplary forces are
defined
absolutely without reference to any mass.