So I’ve been learning physics for quite a while, and this year I got USAPhO gold. Here, I’ll share some thoughts on my journey in physics for anyone interested.
To be honest, I don’t really remember much of it. Like, a lot of times, I got from A skill level to B skill level, without knowing how I got from A to B……
Pre-high-school
I started learning physics around 4th grade, when Mr. Hadzic started teaching us physics lessons during robotics. I was… rather bad at physics, and didn’t really understand that much. We covered some basic kinematics, dynamics, and rotational dynamics at a very surface level, but hey, that was a lot for 4th grade.
After that, I really didn’t touch physics at all for a while. The intuition was pretty useful, though.
Then around 8th grade, I took a physics class, and started grinding f=ma. (wow looking at the homework, i feel really dumb lmao). The physics class covered Hewitt’s conceptual physics. The textbook is ok, it’s very surface level but that’s somewhat expected based on the name, especially for non-mechanics. The class was better than the textbook tho :).
Anyway, that phase of physics was accompanied by a lot of googling (hyperphysics is pretty good as a reference btw, wikipedia is kinda trash), and trying to figure things out when it wasn’t explained in the textbook. Learning stuff this way is kinda painful. Probably, it’d be better to read a good textbook (later on this).
Try not to learn physics the way I did, because my fundamentals were well, to say the least, quite shaky. This would turn into a major skill issue later…
Anyway, I grinded f=ma, but I kinda sucked and I was really slow. And my math knowledge at that time was rather cooked. I was able to take f=ma at walrus, and scored 8/25. that was pretty bad.
Aside on my math knowledge. I knew calculus at a basic level but couldn’t do basic stuff like solve quadratics. At that time my math knowledge was pretty random, tbh, although by the next year it would have improved significantly due to grinding AMC.
High School
In high school, I started seriously-ish studying physics.
In 9th, I started studying physics around December-ish, I think? Maybe I did some physics before then. I think I did some studying during class, and some at home, mostly past problems I think… I don’t think I tried that hard tho, either, esp due to robotics season & usaco season. I definitely got better, though, I think, and faster too. Also, the f=ma was easier. I got 16, cutoff was 18, definitely sillied a few problems, though.
I think 10th grade went similarly, but I [correctly] studied more for USACO than physics, which at that point became a side quest as I aimed for USACO camp. I remember taking the test, and it was pretty bad. The other physics main at our school (MK, a year above me) thought it was bad too. I got 9/25, cutoff was 14… But also, the next day, I like could solve way more, so I think I was being rather stupid during that test.
Between 9th and 10th grades, I forget which, but I remember a specific session of chinese class when Dr. S was subbing (he’s our robotics mentor, and decent at physics). There was this one problem that I couldn’t figure out. Below is the statement:
There is a uniformly solid billiards ball of radius R, on a frictionless surface. Where should you hit the billiards ball, horizontally, such that it rolls without slipping?
Anyway, this problem made me realize how garbage I was at physics. (ok, to be fair to myself, I don’t think Dr. S got it either). My fundamentals sucked. This really didn’t change the way I studied, however. I think most of my fundamental misunderstandings were fixed the hard way, that is, by skill issuing problems and learning why I was wrong.
After USACO Camp, I kinda got burnt out of OI for a while, and I resolved to learn physics and try to USAPhO Camp. Also, I was getting kinda tired of grinding mechanics… I wanted to try something different. So I decided that I was going to read all of Purcell’s E&M book over the summer.
The summer was over with 3 chapters done. Then junior year hit, and we can guess at how that went. By winter I was 5 chapters in. At January ish, I started grinding f=ma again. Anyway… I got 17 correct, cutoff was like 15? I’d finally qualified, on the fourth time taking the test.
I distinctly remember this test. After solving problem 1, I kinda hit a brick wall, as the next problems were the hardest problems in the test. By problem 9, I had solved like 1,4,6,8, and it was around like 30 minutes in, and I was tilting really hard. At this point, I seriously considered rage quitting and walking out of the exam. I’ve only ever felt this way on an olympiad exam a single time.
Well, it was a good thing I didn’t rage quit, because the problems became easier, and I solved through the entire exam.
Anyhow, between 8th and 11th grade I think I’ve finished most of the mocks, i think, I wasn’t really keeping track? I also read (without doing problems) a few chapters of Morin? But that’s a first-order approximation of how much I did, I guess.
USAPhO
At this point I was heavily trolling USACO, and I resolved to commit everything to physics. like, actually everything.
During these two and a half months, I literally dropped everything. I basically stopped going to robotics, didn’t really attend any clubs, and spent all my time grinding physics. To put this into perspective: I literally tanked my APUSH grade by a good 5-7 points, AP lit by like 5 points, and all I did in class was read physics textbooks.
I remember there was state testing or something. I printed the chapter of purcell beforehand, and then submitted the state test in 5 minutes. Then I read purcell for the remaining 2 hours. Those state testing days were very productive.
I got through like chapter 8 of purcell in like 1 month. Then I went to read Blundell & Blundell for thermodynamics. 17 chapters in like 1 month.
There was like 2 weeks left. One week, I solved through a good portion of knzhou T1 and T2. The next week was left to doing mocks.
On mocks, I was pulling a consistent… like half a problem :skull:. Both skill issue and time issue. I also couldn’t solve any relativity at all, or any hard mechanics problems. I was convinced I was going to go in and get a bronze medal or something. And honestly, on any normal test, I definitely think I would’ve gotten a bronze medal.
Day of test. I wake up at like 11, and go to school like 20 minutes before USAPhO. Mr. G makes fun of me for skipping the chem test. I review some of electromagnetism.
The test’s subject distribution ended up being MME MWm, where the lowercase m is math. I solved most of 1 (minus sillies on part 1 and skill issue on last part), none of 2 (oop I forgot to read that morin chapter), most of 3 (skill issued on last part), all of 4, qualitative part of 5, and full 6 (literally following instructions). To this day I still don’t know how I did so well, but it was probably a combination of easy problems, luck, and scuffed topic distribution.
I’m reasonably sure that if I didnt skill issue and silly on problems 1 and 3, then I’d be a camper. Instead, I ended up with a gold medal, but still, that’s much better than I thought I would get, and definitely much more than I deserved……
The week after the test was hectic as well. I had USAPhO, then USNCO nationals, then a shit ton of homework that I procrastinated, then an important math pset too. I procrastinated all of it for USAPhO.
So that was a pretty good answer to the question of how not to learn physics. I guess, the question, is how to learn physics?
First, read knzhou’s advice.
self-explanatory. I won’t cover anything covered in knzhou, really.
Read a textbook, a good one
Textbooks are made to be read, in a way that exposes information naturally for you to learn. Good textbooks are textbooks, but with a lot of thought put into it. Read it. It beats literally everything else, because these textbooks are written by a lot of very smart professors who have a lot of experience teaching this type of stuff, and put a lot of thought into organizing it into a textbook. It’d be quite stupid not to take advantage of this.
Fundamentals matter a lot
You’d be surprised how many people have shaky fundamentals. Get good fundamentals, before you go too deep. Especially in physics, it’s easy to accidentally solve stuff without good fundamentals, but at one point weak fundamentals will come back to bite you. They bit me a lot, and pretty hard.
Also, learn mechanics well. This will help you in other fields of physics.
Learn calculus, well.
You’ll be using it a lot. And if you learn it well, you should find physics to be more intuitive and less nonsensical. This is really a special case of the previous, but it deserves special mention because of how important it is.
Think about everything. Question everything.
Is it physical? How the hell is it physical!?! Where does the energy come from? Why doesn’t it violate momentum conservation? Why the hell does this happen? etc.
Always ask yourself these types of questions. And try to answer them. This is how you check your understanding, and also a good way to approach and explore how a problem works.
If you can’t answer them, it’s likely that a) this is a focal point of the problem, and/or b) you have a fundamental misunderstanding (or c) you sillied).
Also, solving a problem is not enough. You should try to find alternative solutions if you can.
Intuition matters.
You should always be trying to simulate the physics in your head. If you know what happens in a physics problem, you have already solved more than half of it.
some advice I gave a while ago
Oops, I forgot to add this, adding it now. I wrote this in around May or June 2025, hope it is useful.
I used HRK (first 18 chapters) for mechanics (only did some of the problems from the problems section). Morin has harder problems if needed, the blue book is easier and the red book is much much harder.
Purcell for electromagnetism, skipped last 3 chapters (maxwell’s equations, E&M fields in matter). Did most of the problems in the problems section. Requires calculus at minimum, multivariable calculus preferred.
Blundell & Blundell for thermodynamics, did chapters 1~8 (probably not necessary), 11~19. Probably a more challenging read, requires calculus and partial derivatives.
For relativity, Red Morin is recommended, I didn’t read it, but also my relativity is not that good for a reason.
Did not learn waves, or modern. For waves, knzhou handouts should be enough (?)
For other practice problems knzhou handouts are recommended (https://knzhou.github.io/), also past USAPhO problems are pretty good.
I still stand by most of this, but if you want a harder mechanics read, try reading Kleppner and Kolenkow, it’s pretty good
Now that I think about it, I’ve been pretty lucky to get USAPhO gold, but still, I learned a lot of physics, and physics is fun. I’m still not certain how much I will try for physics olympiads this year, but we’ll see, I guess…
