One of the characteristics of any system is its kinetic and potential energy.If a force F has an effect on the body at rest in such a way that the latter is set in motion, there is a commission work dA.In this case, the kinetic energy dT becomes higher, the more committed work.In other words, we can write the equality:
dA = dT
Given the way dR, passed by the body, and developed a speed of dV, we use Newton's second law for the force:
F = (dV / dt) * m
important point: thethe law can be used if taken inertial reference system.The choice of system affect the value of energy.In the international SI system energy is measured in joules (J).
It follows that the kinetic energy of a particle or body, characterized by the speed of movement V and mass m, will be:
T = ((V * V) * m) / 2
can be concluded that the kinetic energy is determined by the rateand mass, actually representing a function of the movement.
kinetic and potential energy is possible to describe the state of the body.If the first, as has been said, is directly linked with the movement, the second system is applied to the interacting bodies.The kinetic and potential energy are generally considered for example, when the power of connecting body, independent of the motion path.In such cases it is important only initial and final positions.The most famous example - the gravitational interaction.But if it is important and the trajectory, the force is a dissipative (friction).
In simple terms, the potential energy is the ability to do the work.Accordingly, this energy can be considered as a work that is necessary to make to move the body from one point to another.That is:
dA = A * dR
If the potential energy denoted as dP, we obtain:
dA = - dP
A negative value indicates that the execution of the work is due to a decrease in dP.For a known function dP is possible to determine not only the power module F, and the vector of its direction.
change in kinetic energy is always associated with a potential.This is easily understood if we remember the law of conservation of energy systems.The total value of T + dP when moving the body always remains the same.Thus, changes in T always takes place in parallel with a change dP, they seem to flow into each other, transforming.
Since the kinetic and potential energy are interconnected, their sum represents the total energy of the system.With respect to the molecules it is the internal energy and is always present, until there is at least the thermal motion and interaction.
When performing calculations selected frame of reference, and any arbitrary time taken for an initial.Similarly, to determine the value of the potential energy is possible only in the zone of action of such forces that when work is done independent of the path of movement of a particle or body.In physics, such forces are called conservative.They are always linked to the law of conservation of total energy.
interesting point: in a situation where external effects are minimal or leveled, any studied the system always tends to its state such that its potential energy tends to zero.For example, the thrown ball reaches the limit of its potential energy at the top of the trajectory, but at the same instant starts to move down, converting stored energy to move, in performing the operation.It should again be noted that the potential energy is always an interaction of at least two bodies: for example, in the example of a ball on a planet's gravity influences.The kinetic energy can be calculated individually for each of the moving body.
