Definitions in Physics #263380

About six years ago the author wrote a pamphlet on Definitions in Physics, which was intended mainly for his own students in the State University of Iowa. The small edition was exhausted in less than two years, since the pamphlet was used in several other universities. In spite of the frequent demands for a new edition, the publication of the book was delayed until it could be thoroughly revised. To write a book of this kind is neither an easy nor a pleasant task. In most cases the only satisfactory definition of a physical quantity is the equation con meeting it with other quantities previously defined. Its concept must be evolved by a backward process, and can become clear only after we have learned all about its measurement and application to physical problems. It will be found that in many such cases the author has not made any attempt to find the deeper meaning of some mathematical relation between two or more physical quantities, however important the relation might have become in our science.