Nabeshin said:
You'd think this, wouldn't you? But in reality it's not very true at all. I know plenty of math majors who are brilliant at math but have no intuitive grasp of physics whatsoever (and vice-versa). To be any good at physics requires a different mode of thinking from my experience, and it is not necessarily synonymous with the mode of thinking required to succeed in mathematics (especially pure mathematics).
Oh yeah. I can vouch for that first-hand. I'm by no means the best math student ever, but I can hold my own, usually being at the top 10% of the class without much difficulty. But when I took Physics last quarter, it was a completely different story. I was lucky to be in the top 30% :|.
Though Physics uses math, most of the math used in Physics problems tends to be easy, comparatively, of course (The types of integrals one gets in a Calculus course tend to be more difficult to solve than the type of integrals one gets in a Physics course). The hard part was understanding a lot of the ideas behind the reasoning to perform such operations.
For example, an introductory Mechanics class deals with ideas such as Kinematics, Forces, Momentum, Circular Motion, among other topics. Most of these require little calculus but quite a bit of high school algebra. And you'd expect most kids to know their algebra pretty well, right? I mean it's usually a high school subject. But even so, many kids have trouble in that class. And I believe it's not so much the math but rather the Physics. I mean once you've got the Physics down, it's "simple algebra."
Edit:
To further clarify, if you know math, it helps in the sense that you won't have to worry about learning two subjects at the same time. But knowing math, I don't think, necessarily means that you'll know or learn Physics quickly.