It could be useful to look at the profile threads that are on these boards. There is one for each year, here is the link to the 2012 one: viewtopic.php?f=3&t=4274
-- it won't be hard to find the other years too.
You can see what kind of profiles get into certain schools and what gets rejected. Just remember that the people who post are probably not a fair representation of applicants -- people who do better tend to be more likely to post!
So if you see something like, everyone who got into School X has a GPA of 3.8 or higher (for example), that doesn't necessarily mean that you need a 3.8 -- there could have been others who had less and got in but didn't post. But, if you see a whole bunch of people with 3.2 applying to School X and all got rejected, then that says something. Ideally, you would want to find a profile that matches yours and then see what places took them. However, you only have 1 year completed, so it would be hard for you to find a match and the applicant pool could change a lot by the time you apply. And some years might be easier to get into than others because of the applicant pool.
I don't think anyone can say a GPA of 3.X is guaranteed good enough for a top 10 school. There are too many other variables (research experience, GRE, LORs, SOP for example) and these schools are super competitive so it will be hard to get in no matter what (unless you are perfect in every way). Most people apply to a wide range of schools: some that they are pretty sure of getting in (i.e. "safety schools"), some that are moderate level for their ability (usually you can find this out by asking your profs, looking at profiles), and some really competitive schools ("reaches"). I think it's worth the application fee to apply to a dream school just so you don't wonder and just so you don't accidentally remove a potential opportunity for yourself!
You are only finishing your freshman year! Most people I know didn't decide on physics grad school until at least 2nd year, and some waited until they actually did some research (end of 2nd or 3rd year). So it's good that you have a goal in mind for your degree, but it could be dangerous since your focus may cause you to miss other opportunities! The first two years of undergrad is a good time to find out what you actually like to study.
One important question to think about is why do you want to go to a top 10 grad school? Sure, the top 10 are really good, and there is some glory to it perhaps, but there are a lot of other really great schools too. Sometimes the best school for your field won't be in the top 10. When it's time to pick grad schools, you would want to pick the best research match as well as any other priorities in your life (maybe you want to be closer/far away from family, certain people, etc.). So I'm not sure why you already seem to have decided that you must go to a top 10 grad school.
But just to kind-of answer your question anyways, if you've read this far down
-- personally, if an undergrad friend, or one of my students with a 3.8+ GPA and some research experience asked me about grad schools, I would definitely advise/encourage them to apply to any of the top 10 schools that have a research match. I would also encourage anyone with a 3.5+ GPA to apply to top 10 schools as a "reach" school. Below 3.5, I wouldn't discourage anyone from applying as reach schools as long as they are also applying to a variety of schools as well. Note that I didn't really answer your question about what GPA is "competitive", though!