<p>Physics is not all string theory. 
I would prepare a long rant on the utility of physics, but that would be [wasting</a> time](<a href=“http://xkcd.com/386/]wasting”>xkcd: Duty Calls).</p>
<p>If you’re only interested in math used in physics, calculus is probably more helpful than most contest math in most applications. (Algebra and geometry do provide a large basis for calculus, though.) If you want to look at computational physics, though, discrete math (counting, probability, number theory, logic, etc.) forms part of the foundation of computer science and is used heavily in math competitions. </p>
<p>FYI, you will have to write proofs in higher math courses, which you are likely to take even as a physics major.</p>
<p>(And if you just memorize techniques for math competitions, you’re doing it wrong. Very wrong.)</p>
<p>EDIT: Never mind, you probably won’t have to write proofs unless you want to or you’re going into an abstract field. From a brief survey of physics major requirements, physics majors usually only need math up through differential equations. Probably assumed that because I’m going to take lots of math, physics, and CS in college, probably majoring in at least one of them, so it all kind of blends in. :P</p>
<p>There are calculus subject tests in some math competitions (Stanford Math Tournament, Harvard-MIT Math Tournament), but for those you also have a Team and Power (proof) round, so…</p>
<p>And why are you doing bio/chem when you could be doing physics on your own? I studied for the AP physics and AP calculus exams without classes, and I did decently; several of my friends have self-studied physics and/or calculus on their own and performed similarly. None of us are geniuses.</p>