To determine the total energy of the movement of a physical body or interaction of elements of a mechanical system, it is necessary to put sizes of kinetic and potential energy. According to conservation law this sum does not change.
Instruction
1. Energy – the physical concept characterizing ability of bodies of some closed system to make a certain work. Mechanical energy accompanies any movement or interaction, can be transferred from one body to another, being distinguished or absorbed. It directly depends on forces operating in a system, their sizes and the directions.
2. Kinetic energy Ekin is equal to work of driving force which reports acceleration to a material point from a condition of rest before acquisition of a certain speed. At the same time the body receives the work stock equal to a half of the work of mass of m on v speed square²: Ekin = m·v \.
3. Elements of a mechanical system not always are in the movement, also the condition of rest is peculiar to them. At this time there is a potential energy. This size depends not on the speed of the movement, and on position of a body or arrangement of bodies from each other. It is directly proportional to height of h at which there is a body over the Earth's surface. Actually potential energy is reported to a system by the gravity arising between bodies or between a body and the earth: Epot = m · g • h where g is a constant, acceleration of gravity.
4. Kinetic and potential energy counterbalance each other therefore their sum is always constant. There is a law of energy conservation according to which total energy always remains to a constant. In other words, it cannot arise from emptiness or disappear in anywhere. To determine total energy, it is necessary to unite the given formulas: Epol = m·v \+ m · g • h = m • (v \+ g•h).
5. A classical example of conservation of energy is the mathematical pendulum. The applied force reports work which forces the pendulum to be shaken. Gradually potential energy formed in the field of gravity forces it to reduce amplitude of fluctuations and, after all, to stop.