++ Q: Calculate the force on the tabletop under such-and-such
conditions. This is a question about the physics.
-- Q: In such-and-such complicated situation, identify which
force is equal-and-opposite to this other force. This is
probably intended as a question about the model.
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I would need a lot more convincing that a reasonably clear and useful
distinction can be made between questions about *physics* versus
questions about *models*.
Are you classifying the first question as *physics* because it involves
a concrete measurement, for example? If so, that take on physics is easy
to argue against, so I'm pretty sure that's not what you mean.
I am trying to think of a situation where I can say I understand the
physics of the situation without reference to any particular model. I
just don't know what that type of understanding would be like.
The very idea of an object on a tabletop having a 'force' on it, for
example, is a manifestation of a chosen model. Before Newton we
conceptualized that problem differently. In fact your posts about
momentum flow recommend thinking about it differently too. So what makes
that first question physics 'proper'?
The more I learn about physics the more I become convinced that it is
pretty much all about models: constructing them, analyzing them,
criticizing them, generalizing them, and so on. The models, to be sure,
are models *of* the real world, but the physics seems to me to be
located in, or at least inextricably interwoven with, models.
I suspect I just don't quite understand where you're coming from on this
issue.