Any science at all can be made into a formal scheme applicable in entirely different domains, a kind of general paradigm. This is especially so with natural sciences, which extensively employ mathematics in their special models. However, such scheme transfer should obey certain rules, to avoid reductionism; the formalism has to be adapted to the new application area, properly reinterpreted in the terms of the target science. In this report, I illustrate the general principles of interdisciplinary scheme transfer on the sample case of applying the scheme of Newtonian mechanics to the psychological theory of motivation dynamics. The perspectives of the extensive use of physical models in psychology are discussed, to overcome the traditionally psychophysical approach and develop a new direction of research that could be called physical psychology.