It is not necessary to distinguish between inertial and gravitational masses believing that the nature has chosen them quite proportional to each other by chance, and not necessary to believe that the nature by chance has chosen the power of distance in inverse-square forces exactly equal to two, and not necessary that in trying to define mass (and force) to become involved in a vicious circle using presupposition of existence of inertial reference frame which itself requires pre-definition of mass. Newton's laws of motion are rewritten in a logical manner. Some primary models are presented as guides for discovering the essence of known forces. A model for justifying the force between two electric and magnetic charges, moving relative to each other, is presented. In fact energy has only one form: kinetic energy. The law of action-reaction holds completely and undoubtedly only during the direct collisions of particles.