Total mechanical energy of bodies and systems

A quantity that equates to half of the product of the mass of a given body by the speed of this body in a square is called in physics the kinetic energy of the body or the energy of action. The change or inconsistency of the kinetic or motive energy of the body over a period of time will be equal to the work that has been performed for a given time by a certain force acting on the given body. If the work of any force on a closed trajectory of any type will be zero, then a force of this kind is called a potential force. The work of such potential forces will not depend on which path the body moves. Such work is determined by the initial position of the body and its final position. The origin point or zero for the potential energy can be chosen absolutely arbitrarily. The value, which will be equal to the work completed by the potential force for moving the body from a given position to the zero point, is called in physics the potential energy of the body or the energy of the state.

For various types of forces in physics, there are various formulas for calculating the potential or stationary energy of the body.

The work done by the potential forces will be equal to the change in this potential energy, which should be taken in the opposite sign.

If you combine the kinetic and potential energy of the body, you get a value that is called the total mechanical energy of the body. In a situation where the multiple-body system is conservative, the law of conservation or constancy of mechanical energy is valid for it. The conservative system of bodies is a system of bodies that is subject to the action of only those potential forces that do not depend on time.

The law of conservation or constancy of mechanical energy is: "During any processes that occur in a certain system of bodies, its total mechanical energy always remains unchanged." Thus, the total or entire mechanical energy of any body or any system of bodies remains constant if this system of bodies is conservative.

The mechanical energy of any system that consists of n points continuously interacting with each other is equal to the sum of the potential stationary and kinetic driving energy of the system of points. If the system of these points is in an external field in which conservative or constant forces act, then the total mechanical energy of this system is equated to the sum of the potential stationary and kinetic driving energy with the addition of the potential energy of the given system to the external field. If there are nonconservative forces in the system, then the total mechanical energy of the system can not be preserved, but begins to decrease and its loss is equal to the work of non-conservative forces in this system.

If only non-conservative forces act on the particle in the system, then the sum of the potential and kinetic energy will remain. But at the same time, interconversion of energies in the system is possible. Potential energy can turn into kinetic energy, and kinetic energy can become a potential energy.

The law of conservation or constancy of total or all mechanical energy is always invariant, that is, its form of recording does not change, even if the starting point of time is changed. This is a consequence of the law of time homogeneity.

When dissipative forces begin to act on the system, for example, such as the friction force, then the mechanical energy of this closed system gradually decreases or decreases. Such a process is called dissipation of energy. Dissipative system is a system, the energy in which can decrease with time. During the dissipation, the mechanical energy of the system is completely transformed into another. This fully corresponds to the general law of energy. Thus, in nature there are no completely conservative systems. Necessarily, in any system of bodies or material points, this or that dissipative force will take place.