I agree with Nick that it is worth discussing Conceptual Physics courses.
Nick seems to have come down on both sides of the argument. While he
advocates the offering of "conceptual" physics courses, he insists
that they must be mathematically well founded, and to achieve this
goal he suggests teaching fewer topics but teaching each more deeply
using appropriate mathematics. I don't know quite what to say. I
agree with him, of course. Does Hewitt approach it this way in his
book, which I have always taken as the defining standard of the
misnamed "conceptual" physics (Orwell would have liked that one)?
Presumably Nick took his students through linear kinematics before
treating the two-dimensional problem of projectile motion. I consider
the latter problem to be too sophisticated for a first course for
students with limited mathematical ability, the target audience for
"conceptual" physics as I've been assuming. Nick is teaching what I
would teach to a first year university physics class which has a
corequisite calculus course. (Of course calculus is not absolutely
necessary for the analysis of projectile motion, it certainly helps
to have been exposed to linear kinematics through calculus.) He is
teaching *real* conceptual physics. Sice he is doing that he should
(in my opinion) refrain from making assailable propositions such as
the unqualified comparison of the times of fall of bullets.
Leigh
(I thought John Mallinckrodt's observation about a retarding force
having a greater than first power velocity dependence providing
effective lift to be a revelation here. I'd never heard of such a
thing, but it is obviously true - and significant. It explains for
me why bullets fired from a rifle don't fall with acceleration g.
I have written an authority for information on this topic and I
will, of course, share it when I get it.)