Long story short, I just finished Physics I. Since I'm currently attending a state college, I have been trying to study outside of my coursework in order to optimize my education and have the best chance of getting into top grad schools. One of the resources I was trying to use was MIT's opencourseware Physics course from Walter Lewin. Now just to give you a bit of a background here, my math level is up to single-variable (I have multi-variable and ODE next semester). I also finished my Physics I course with a high A. However, while some of the material Lewin covers is easy for me, there are some things he does mathematically that go over my head. This is really frustrating to me since I have never struggled with anything previously. Even with Calc II, I only spent 2hrs studying for our final and got a 100 on it. However, with Lewin's lectures, I feel like some of the mathematical derivations he uses is over my head. I remember a lot of the formulas at this point through the concepts and am not sure if I am falling short of being up to par with what MIT would expect? I recognize or can derive some of what Lewin does at times, but sometimes, I just can't follow him from point A to point B in his lectures. I am planning to apply to places like MIT for grad school, so I want to make sure I'm not falling behind at this point. I have heard some professors will talk over your head since they will give you mathematics you may not have gotten to yet or such, but I am just not sure if he is one of those professors. I'm wondering if once I get through multi-var. calc and ODE if it will help the mathematical derivations make more sense, or if I should be utilizing some kind of resource to get better at that myself?