Physics stands for the hidden laws that make things move. A physics class in a dream is read as trying to understand the forces at work in your own situation.
Where in your waking life have you met something like this lately?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.