The Feynman lectures on physics is a transcript of some of the lectures Feynman gave at the California Institute of Technology to freshman and sophomore students. It was somewhat of an "experiment"; feynman had never done this before. He purposed to adress these lectures to the most "intelligent" of the class. It should be no surprise that these lectures are difficult. Caltech students are among the highest scoring on the math college boards of the country; they can handle the math, so often used in these lectures. Feynman often assumes knowledge of certain subjects. These are some things that are helpfull to understanding the content the first volume: equation of oscilliating spring, Newton's equation of gravitation, fundamental algebra, trigonometry, a couple theorems of geometry... Calculus is definately helpfull to know, as Feynman's lecture on its principles is just a reminder to the students he was adressing, most of which were already proficient in the matter. These things aside, this texbook is one of the best college texbooks you can get; lucid, interesting, and very challenging. Feynman at his best; he can be quite humourous at times: i personally love it when he makes fun of the philosphers. So buy the book, but don't get discouraged if it's hard.