I like doing physics problems and some math problems myself. The reason I like it is: (1) It's very fulfilling to get it right, especially when it's recognized by Baidu. (2) The rigor and logic of physical and mathematical problems are realized in solving problems, which makes you happy physically and mentally. (3) In solving problems, we can obtain the knowledge and principles of common things that we didn't know before. (4) Get knowledge from physics problems and make some small toys. (5) Learn some new knowledge and set an example for your younger generation.