To the reader! This brochure - the latest in a series - is extraordinary. All year our readers received information about new problems of physics, astronomy, mathematics, about the latest achievements and discoveries. And now we give them the opportunity to learn about themselves. "Do you know the physics?" - so it would be possible to title the brochure of academician P.L. Kapitsa. But that title would probably prove too simplistic. Kapitsa's problems are sometimes very difficult, and not solving them does not mean not knowing physics. But they are not such that they cannot be solved by a newcomer. Some of them are even quite simple. But none will succumb to you if you do not know how to delve into the essence of the physical process. Many problems are so meaningful that a detailed solution to them with analysis turns into a small scientific study. As you can see, full of diversity. But try to figure it out. And if you succeed, you can declare: - I understand physics.