Brush the problem, that is, bow your head and do it in a daze, and the understanding of the problem and the application of physical theorems (principles) are not very clear.

So, if you are bored, brush it for a week or so, and then you will calm down, and then you can do some problems well: the so-called understanding problems are mainly to do some ground problems in different categories, and realize what you have gained when doing these problems and after finishing them.

Note: You can feel that you have gained a lot, so don't worry about getting full harvest and satisfaction-this is also the true meaning of learning ~