I took the class during the covid pandemic, so your experiences may vary from mine.

An is a very good professor and was able to explain the material fairly well. It was his first time teaching this class, but I think he did a great job. In the first few lectures I felt that his explanations were very math heavy, and if you haven't taken 32B it might be hard to understand the math behind the explanations. He will only get better in the future.

An was very lenient during the pandemic, an he was willing to make compromises for the well-being of the students which is good to know. He gave 24 hour midterms, but decided to go back to 3 hours for the final since the midterms got leaked on chegg, which I feel was an appropriate response, albeit a bit harsh to international students.

My advice for the class is to do the discussion worksheets he gives out every week and make sure you understand them really well. Also pay attention and really internalize the concept test slides he puts on ccle, since his exams not only have problems with numerical or symbolic answers but also short answer questions which test your understanding of the big picture. And also do the challenge problems from the textbook.

An is a great professor, and he will only get better. If you have the chance to take him, I suggest you do

Professor An is a really nice person. I've had so many email conversations with him, often asking the same question multiple times, and he would always respond to me with the same patience until I didn't grasp the concept.

His lectures were sometimes confusing, not because he explained it bad but because they involved math that wasn't covered in the prerequisites of the class. To understand the proofs you might need better knowledge of math (would recommend 32B). That said, the questions in the exam never asked about the proofs, just the applications of the formulae, so you'll be fine in the class without really understanding where the proofs come from.

His tests were quite fair, however they were lengthy. Considering this was probably his first time teaching at UCLA, he might pace his tests better in the future based off of the feedback he received (after a class complaint for the second midterm, he made the final exam easily doable in 3 hrs). And he receives feedback quite sweetly, and recognizes his shortcomings! Honestly that makes him a great instructor. His office hours are great too and his love for physics is visible over there; a single topic can take him through the entire hour (if nobody else is there).

Grading was straight scale, but still generous. Exam scoring was also very generous. For questions that were hard, he gives extra credit but doesn't penalize if you did bad on it.

He gave 12 initially and later 8 questions per week on Mastering Physics. He'd throw in a challenge question or two in there and would be happy to explain it. Not too much workload as compared to many other professors who teach physics 1B.

Would recommend taking his class if
a. you just want to get over with the class with a good professor
b. you don't want to take Corbin at any rate
c. you have knowledge of the required math that isn't a prerequisite for the course (ie complex number and multivariable integration)

I found this class difficult mostly due to the fact that I'm an international student and all my classes were in the evening, making it hard for me to focus. He was an alright lecturer, most times he relied a lot on mathematical derivative which most students didn't understand yet so it seemed a little boring and confusing, but he put out example questions during lecture for students to answer so he could get a grasp of everyone's understanding, which was nice. I ended up just copying notes from the textbook, but it didn't go too well.
The first midterm was fine, but the second midterm was a lot more difficult than everyone thought it would be, so when we emailed him about it he was very understanding. The final was made optional in the end, so I didn't take it since it wasn't worth the mental exhaustion of taking a 24h final to not make my grade budge.
Overall a very understanding and lovely professor. If you're not the most confident at physics, I would suggest taking him.

I took this class online due to COVID-19. I found the lectures kinda confusing, so I would just read the textbook and do the homework each week and go to discussion for doubts. Homework was very time consuming. The midterms were a bit easier, but took a lot of time. He seems super nice and very willing to help, but i just didn't vibe with his lecture style.

Honestly, the only reason I managed a B in the class is because of the 24 hour exams. Physics is not my strength, so I struggled in this class, but Prof. An is always super helpful. If you're struggling in the class, you can email him at any time and he'll try his best to help you. He's super kind, and listens to his students. For example, a lot of us were struggling on a certain problem on the second midterm, and after many emails, he decided to make it extra credit. The workload was alright, but we use mastering physics, which is a pain. His discussion worksheets are difficult, but definitely prepare you for his tests. Since it is largely conceptual, his conceptests (basically just slides w/ questions, not an actual test) really help too.

The only reason why I did so well in this class was because of the 24 hour midterms. I learned all of the content in 24 hours and although it was rough (I spent 14 hours on the second one), lectures weren't too helpful and neither was the Mastering Physics homework because the tests are mostly conceptual and use variables and the homework usually uses numbers. Do the homework though because it's easy points and the hints they give you basically give you the answer. I stopped going to lecture after the first midterm because basically you can do well if you look at the conceptests, discussion worksheets and notes he gives because the tests are either the same or very similar to all of those. He was very nice and it was the first time he has taught, but I know he wants his students to do well. He always listened to our concerns and responded well. His office hours were also very helpful, he basically explained the homework to me and worked it all out and when I emailed him, he wrote out a very thorough hint which was really helpful. Honestly take him if it's online and you have 24 hour midterms because otherwise you have to put in a lot more work outside of class trying to understand the stuff because physics in general is just hard.

Although Professor Xin is a really nice guy and did a really good job of improving his teaching style and making accommodations based on our feedback throughout the quarter, this class was still the most stressful class I've ever taken at UCLA. Since this was the first undergrad course he had taught, the lectures during the first few weeks were really confusing for me and focused on unnecessary things. I ended up failing the first midterm (a combination of being confused from lectures, studying the wrong things, and not being thorough enough with my answers). This caused me to be incredibly stressed out because I was worried about passing the class in general, forget about getting a good grade. Professor Xin's lectures improved over time, I studied really hard for the second midterm, and I ended up doing above average. For some reason the professor refused to curve our grades at all which was another big source of stress bc I did so poorly on the first midterm. There was also a lot of last-minute back-and-forth with his decisions to how grading would work. Only a couple days before the final, he decided to change the 24-hr final to only be 3 hours to try and combat cheating, which I think was inconsiderate especially because he sent out the decision the day before the deadline to change grading status to P/NP, and a lot of people were worried about which grading they should go for. It took a class-written email with all of our signatures at the bottom for him to make the final no-harm, even when other 1B professors had already decided to do it that way, as well as the Academic Senate urging professors to be lenient with finals.

All in all, I'm sure the next class Professor Xin teaches will be handled a lot better than this one was. But the fact that he's a nice guy doesn't really make up for all the stress that this class caused me.

This was Professor An's first quarter teaching undergraduate students, and he had previously only taught graduate level physics. So he had difficulties adjusting to a level at which we could understand him at the level of a lower-division class. However, his lecture style greatly improved at around Week 4, when he began to put aside complicated differential equations and instead focus more on a conceptual style of teaching. He actually improved even more when we moved on to the electricity portions of the class, and I began to really like his attention to detail and the way that he structured the class (introduce concepts with video demos, do a few examples in class, show exceptions/summarize, then do clicker questions).

Participation didn't matter in the class or discussion sections: grades were solely determined based on Mastering Physics assignments (15%), midterms (25% each), and the final (35%). He ended up making the final optional because of the pandemic and protests, so you could only receive the higher of the original grade breakdown or just the homework and midterms. I'd highly recommend doing his discussion worksheets, even though they are quite difficult, because that's the content that he tends to put on his exams. He is extremely willing to help students and was very accommodating in the online setting. Not many people went to office hours, so whenever I went, he was willing to answer any question I had (he even spent an hour going through one discussion worksheet problem with me).

In short, I wish he improved earlier (the first midterm kind of scarred my grade, although I was still able to recover), but I trust that he'll continue to adapt his style to students' needs in the future. So don't be afraid to take his class!