Effect of a Non-Zero Velocity of the Motion Frame on the Kinetic Energy of a Free Particle Examined with the Aid of the Relativistic Mechanics

The paper examines the change of the relativistic kinetic energy of a free particle due to the velocity change of the motion frame in a special case when this reduction leads to the kinetic energy equal to zero. The difference of velocities gives a functional dependent solely on the velocity frame and original velocity of the particle. An analysis applied to the functional gives simple formulae for the extremal values of the mentioned velocity parameters. In the next step, solutions of the equation presented with the functional provide us with the velocities necessary for the vanishing property of the kinetic energy. A characteristic point is that a condition of the velocity of the motion frame smaller than the velocity of light is obtained directly in the applied formalism. This property holds with no reference done to the well-known postulate of the dominant value of the light velocity entering the relativity theory.