Energy – the physical concept accompanying any movement or activity. This parameter in conditionally closed system is invariable size irrespective of the interactions between bodies happening in it.
Instruction
1. Any movement or direct interaction of physical bodies is followed by allocation, absorption or transfer of mechanical energy. Elements (bodies) of a mechanical system can or be in the movement, or at rest. In the first case speak about kinetic energy, in the second – about potential. In the sum these sizes are the total mechanical energy of a system: Σ E = Ekin + Epot.
2. Kinetic energy represents work of force which application gives acceleration to a point from zero to final speed, it is possible to find it on a formula of the semi-work of weight on a speed square: Ekin = 1/2·m·v \.
3. If the kinetic component of mechanical energy depends on speed, then potential – on a relative positioning of bodies in a system. I.e. in order that there was this energy, in a system there have to be at least two elements. Not what this size is equal to makes sense and as it changes. The bodies which are in the field of an attraction of Earth have potential energy: Epot = m · g • h where g is acceleration of gravity, h is height of position of the center of body weights.
4. The sum Σ E is always a constant. This law is respected in all mechanical systems irrespective of its scales, and it consists in conservation of energy.
5. The potential energy depends not only at most inclinations, it also accompanies elastic deformation of a physical body, for example, of compression/extension of a spring. At the same time it is thought differently, proceeding from rigidity of a spring of k and its lengthening x: Ekin = k·x \.
6. Electromagnetic energy is divided sometimes into electric and magnetic though in most cases they are closely interconnected. Actually mean density of energy of the electromagnetic field by this term, and find the general energy of this field by summation electric and magnetic: Eem = + H · B/2 where E and H are tensions, and D and B – induction electric and magnetic water E•D/2 respectively.
7. The formula of gravitational energy is a consequence of Newton's law of gravitation according to which two bodies which are in half of Earth are affected by the gravitational force of interaction. When calculating energy of a system of such bodies or elementary particles gravitational constant G, distance between centers of the mass of R and, actually, the mass of two bodies of m1 and m2 are used: Egrav = - G • (m1 • m2) / R.