Kinetic energy: concept

The kinetic energy is, by definition, a value equal to half the mass of the moving body multiplied by the square of the velocity of this body. This is one of the most important terms of modern mechanics. To put it briefly, it is the energy of motion, or the difference of total energy and rest energy. Yet its essence is not fully understood in modern science.

Kinetic energy (from the Kinema group - motion) of a body in a state Is equal to zero. Often this value is associated not only with mass and speed. So, according to one definition, kinetic energy is a work done at a certain speed. It is measured in joules.

The kinetic energy of a system is a quantity that is closely related to the speed of each of its points.

It is considered both in the forward motion and in the rotational motion. The first case has already been explained in detail above, this is half the mass of an object multiplied by its speed in a square. And the kinetic energy of the body's rotation is represented as the sum of the kinetic energies of each of the elementary volumes of a given body. Or as the value of the moment of inertia multiplied by the square of the angular velocity divided by two.

Suppose there is some solid body that makes a motion around the axis Fixed, passing through it. This object can be divided into small elementary volumes, each of which has its elementary mass. Around the fixed axis, the body under consideration makes movements. Each of the elementary volumes describes a circle of the corresponding radius. The angular velocity of their rotation is the same. And therefore the kinetic energy of a given body is the sum of the kinetic energies of all its elementary volumes moving around the axis. A simplified version of this formula is half the product of the square of the angular velocity and the moment of inertia.

In some cases, the kinetic energy is the sum of both translational and rotational energy. For example, sliding without sliding on an inclined line cylinder. Moving forward, it performs translational motion, however, while it also moves around its axis.

One of the components of the kinetic energy of rotation is the moment of inertia, about which it was mentioned above. It depends on the total body weight, as well as on its distribution with respect to the axis of rotation. What is it? This is a measure of the inertia of movement around the axis, just as in the forward motion the measure of inertia is mass. This is a very important quantity. The greater the moment of inertia, the more difficult it is to bring the body into a state of rotation. The angular velocity characterizes the speed with which the solid moves around its axis. The unit of measurement is rad / s. The angular velocity is the ratio of the angle of rotation to the time interval over which this angle passes through the rotating object.

The kinetic energy theorem can be formulated approximately as follows: the work of a force that acts on a certain body is equivalent to a change in the kinetic energy of a given body.