In physics, angular momentum is defined as a vector quantity that indicates the state of rotation of bodies around a fixed point. This physical quantity is present in classical, quantum and relativistic mechanics. The angular momentum is measured in kg.m2 / s. This measure plays a role similar to linear momentum in translations.
Within classical mechanics, the angular momentum of a molecule or point mass relative to a point or space represents the linear momentum p with respect to its point. It is usually represented by the symbol L, where r is the line that joins the point o with the location of the point mass. To determine the angular momentum in classical mechanics, the following formula is applied: L = r X p = r X mv.
As can be seen, the angular momentum of a point mass is not a measure of the body, but is subject to the reference point chosen. Its physical concept is linked to rotation, since angular momentum represents the state of rotation of a material point, in the same way that linear momentum represents the state of linear translation, but in order to understand this concept a little more, it is necessary to know a new measure: the moment of inertia.
The moment of inertia of a point mass is defined as the product of the mass of the body itself and its distance from the axis of rotation. This measure is expressed as follows: I = m X r2. For example, there is the case of the Earth which rotates on its imaginary axis, here the total angular momentum is the sum of the angular momentum of itself, on its own axis and around an imaginary axis of the center of mass of the Earth system. -Sun.
The angular momentum is a measure that is maintained, that is, the sum of the angular momentum transferred from one body to another in a closed medium, will always give zero. This can be seen in the rotation of the body around its center of mass. Rotating the body and with the arms open, it can be observed that the speed is persistent, but, if the arms are closed, an increase in speed will result. It is for this reason that the moment of inertia is higher when the arms are open, since the distribution of body mass is far from the axis of rotation.
