Read online (free for all) or download. Or buy the hardcopy.
a) This is written for high-school students.
b) It is very high quality, far above anything else I've
seen at the introductory level. Systematic, well organized,
no nonsense. It's 50 years old but not out of date IMHO.
The end-of-chapter exercises are pretty good (unlike in
most texts).
Nowadays "conceptual" physics is a euphemism for qualitative
gee-whiz numbskull physics, but PSSC is /conceptual/ in the
most positive sense: It expressly discusses the fundamental
concepts (as opposed to working through a bunch of examples
and hoping the students will pick up the fundamentals by
osmosis).
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Suggestion #2: Read the little book "Character of Physical Law"
or watch the videos of the Messenger Lectures that Feynman
gave, which form the basis for the book. This is aimed at a
general audience, not hard-core physics nerds, but it gives
a good flavor of what physics is about.
This is inspiring stuff. People have mentioned during their
Nobel lectures how they were inspired by these books, in terms
of style as well as substance. Style as in panache, and an
appreciation for the power and grandeur of physics.
A highly motivated high school student should be able to read
most of Volume I. Note that back in 1961, calculus was not an
admission requirement at Caltech or even a prerequisite for
freshman physics. It was a corequisite.
On the other hand, this is not physics for dummies; this is
physics for smart people who want to get smarter. It *is* for
hard-core physics nerds.
Warn the student: Skimming is a skill. Nobody is born with this
skill. Learn how to skim. Don't panic when you come to something
you don't understand. Just make a mental note of it, and if you
need it later you can look it up. Seriously: I've read the Feynman
books about six times, and I learn something new each time.