The kinetic field theory (KFT), which does not contradict observations, conservation laws and equations of the general theory of relativity (GRT), was constructed. Objections of A. Poincaré and other scientists against a similar attempt by J. Lesage (1784) were eliminated by assuming that the background particles responsible for the transmission of gravitational, inertial, electric, magnetic, electromagnetic and some other types of information have a strongly elongated needle-shaped (interobraznyi) form. Among possible applications of KFT are the use of background particles as an inexhaustible and environmentally friendly source of energy, control of tectonic processes in order to provide people and pets with safety during earthquakes, and many others.

The solution of problems associated with the study of kinematics, dynamics, and energy of free, unsubmerged liquid jets is associated with a number of specific difficulties. These jets differ from many other types of motion of a continuous medium in the presence of a free surface, the shape of which changes with time according to some previously unknown law.

To predict the places of greatest wear on the walls of the ore pass, to determine the kinetic energy of falling pieces of ore, the possible degree of crushing of the material during transfer, and to solve some other problems, it is necessary to know the kinematics of the movement of an individual piece of ore in the ore pass.

Practice shows that in ore mines, where mass explosions are used for stripping of useful minerals, the maintenance of mine workings causes significant difficulties, which increase with increasing depth of development.

An unsteady axisymmetric non-swirling flow of an incompressible ideal fluid in the absence of body forces is considered. The problem is solved in a cylindrical coordinate system (r, φ, z), the origin of which coincides with the center of a circular outlet of very large diameter, the z‑axis with the axis of symmetry of the flow, and the position of the plane φ = 0 is immaterial due to axial symmetry.

At the end of the XIX century researchers pointed out the internal instability of a free jet caused by capillary forces applied to its surface.