## kinetic energy

kinetic energy of the body is called the physical quantity that is equal to half the product of the mass of the body on its velocity squared.It is the energy of motion, it is equivalent to the work that must make the force applied to the body at rest, in order to inform him of the set speed.After impact, the kinetic energy can be transformed into another form of energy, for example, sound, light or heat.

Adoption, which is called the theorem of kinetic energy, says that it is the work of a resultant change in the force applied to the body.This theorem is always valid, even if the body moves under the influence of constantly changing force and its direction does
not coincide with the direction of its movement.

## potential energy

potential energy is not determined by the speed and the relative position of bodies, for example, relative to the Earth.This concept can be administered only to those forces whose work does not depend on the trajectory of the body, and is defined only by its start and end positions.Such forces are called conservative, their work is equal to zero, if the body is moved along a closed path.

## Conservative forces and potential energy

gravity and the elastic force are conservative, they can introduce the concept of potential energy.The physical meaning is not the potential energy and its change when moving the body from one position to another.

change in the potential energy of a body in a gravitational field, taken with the opposite sign, equal to the work that makes the force to move the body.When the elastic deformation of the potential energy depends on the interaction of body parts to each other.With certain reserve of potential energy, compressed or stretched spring can drive the body, which is attached to it, that is, to inform him kinetic energy.

addition to the elastic forces of gravity and property conservatism have other forces, for example, the strength of the electrostatic interaction between charged bodies.To frictional force the concept of potential energy can not enter, her work will depend on the distance traveled.