Total mechanical energy of a body is the sum of potential and kinetic energy which is peculiar to any physical body in each timepoint. Their ratio can change, but the sum of two of these types of energy always remains to a constant.
Instruction
1. In the beginning it is necessary to count potential energy of a body, it is called still energy of rest. It is calculated on a formula: P=m*g*h (work of weight, height and acceleration of gravity) where m is body weight, g is the acceleration of gravity equal 9.8H/m, h is height on which the body is raised above the ground. If its remoteness from the Earth's surface as points of support, it is equal 0, then potential energy is equal to 0 too. Thus, if the body is suspended over a surface at a certain height, then it has positive potential energy. If it is below a surface, that is, underground, that its potential energy is negative (on its rise on zero it will be required to height additional expenses of energy).
2. Kinetic is an energy of the movement of a body, that is, only the moving objects (having speed) have it. Calculation formula following: E=m*V^2/2 (the work of body weight on a square of its speed, divided on 2) where m is body weight, V – the speed which the body at the time of calculation has. If the body is not movably fixed on a suspension, or it is based upon a support, then kinetic energy is equal 0 as speed is absent. The more speed and body weight, the more its kinetic energy.
3. To find total energy, it is necessary to put kinetic and potential. Following formula: Ep =P+E=m*g*h + m*V^2/2. Usually physical body is at rest, but is removed from Earth so it has only potential energy, kinetic is equal 0 (for example, the suspended cargo). The body moving on the Earth's surface has only kinetic energy, potential is equal 0 (for example, the going car). But if the body is in flight, then value of both types of energy – nonzero.