Principle of Minimal Energy effect

Nowadays, it is familiar to designers to use a numerical method for design, optimization or verification of technical device parameters. The well-known software resources are built on principles of finite or boundary elements (or finite differences several years ago). These methods (especially the Finite Element Method - FEM) have been built on common basic principles; the most important is the Principle of Minimal Energy (described eg by R. P. Feynman in 1966). The basic ideas of the Principle of Minimal Energy will be presented in the paper, followed by practical examples. The reader will be able to follow the principle and build an understandable theory on professional numerical methods basics, theirs possible advantages and disadvantages and shortcomings. The main idea presented in the paper is based on very simple example - motion in the gravitational field of the earth.