The simplest form of movement is a mechanical movement of bodies. For a quantitative description of this movement, it is necessary to identify relevant characteristics associated with the concepts of space and time. Both space and time are complex physical concepts, the meaning of which can be revealed only within the framework of special and general relativity. Kinematics is a part of mechanics, which deals with the motion of bodies regardless of the causes of the movement.
As a special branch of theoretical mechanics, kinematics emerged later than statics and dynamics. Namely, it was at the beginning of the second half of the XIX century. The appearance of the first studies of kinematics is associated with the invention of firearms. Primarily, researchers’ attention was attracted by the questions of the definition of the flight path of the projectile, clarification of the concepts of irregularity, and curvilinear motion of a point. Leonardo da Vinci was the first who experimentally studied the issue of free vertical fall of a heavy body. However, only due to the works of Galileo Galilei, the development of mechanics has been closely associated with the demands of the technology of the time. Galileo introduced the concept of acceleration and a proof that the motion trajectory of a projectile thrown into the void at a certain angle to the horizon is a parabola. Laws discovered by Galileo have been developed in the studies of Evangelista Torricelli. He established a formula of proportionality of the velocity of a falling body of the square root from the height of fall. The generalization of the concept of acceleration in case of curvilinear motion was made by Christiaan Huygens. He first drew attention to the possibility of the partition of acceleration in curvilinear motion into tangent and normal components (Chester 57-58).
Two major concepts of kinematics are velocity and acceleration. It was proven that velocity is a measure of the mechanical condition of the body. It characterizes the rate of change of position of the body relative to the system of indication and is the vector physical quantity. Average velocity is the vector physical quantity that is numerically equal to the ratio of the movement and to the length of time over which it occurred. Moreover, it is directed along the displacement. Acceleration is the vector physical quantity that characterizes the rate of change of velocity. It shows the value of speed changes of the body per unit of time. Average acceleration is a physical quantity that is numerically equal to the ratio of change of speed and the time in which it occurred (Chester 58-60).
Another important concept of kinematics is the motion of electric charge. Electric charges consist of ordered motion of electric currents. Electric charge is a physical quantity characterizing the electromagnetic interaction. The body is negatively charged if it has an excess of electrons, and it is positively charged if there is the deficit of electrons. “The movement of a positive test charge within an electric field is accompanied by changes in potential energy” (“Electric Field and the Movement of Charge”).
At the heart of many phenomena occurring in the Universe, there are events associated with the movement of electric charges. The first phenomenon associated with the movement of charged particles in the Earth’s magnetic field is an aurora. Auroras are most frequently observed in high northern latitudes. However, they sometimes can be seen in southern latitudes. The light in auroras is generated by solar protons penetrating into the Earth’s magnetic field up to altitudes of about 100 kilometers (Giordano 611). At these altitudes, the atmosphere is extremely rarefied. Nevertheless, it still contains enough oxygen and nitrogen atoms. Proton collisions with these atoms provoke clearly visible glow. Although auroras occur continuously, but usually the intensity of the emitted light is not sufficient for observation. Only when there are strong disturbances on the Sun, the number of protons that reach the upper atmosphere increases dramatically. Thus, a person can watch auroras. The second phenomenon is lightning, which is associated with the motion of charged particles. “During a lightning strike, large amounts of electric charge move between a cloud and the surface of the Earth or between two clouds” (Giordano 610). The length of the lightning reaches several kilometers. Their diameter is usually several tens of centimeters, and the length is tenths of a second. Lightning is usually accompanied by thunder.
Apart from physics and mechanics, kinematics is also applied in modern technologies, biology, medicine, and everyday life. People constantly meet the movement of bodies in everyday life, technology, and science. There is the movement of people and animals, of water in rivers and seas, as well as of air. It is committed by various means of transport, all kinds of mechanisms, machines, and tools. Almost all physical phenomena are accompanied by movements of the body. A vivid example of kinematics in medicine and biology is the dynamics of the foot. It is the interaction of forces acting on the foot, as well as loads and stresses that arise during the impact of these forces. A foot is an integral part of biomechanical system related to musculoskeletal system, and its dynamics cannot be viewed in isolation from the system. The dynamics of the foot is a derivative of the movements of the musculoskeletal system – kinematics. The most typical human movement associated with the load of a foot is walking (Chester 67-68).
Kinematics is a special branch of theoretical mechanics. Many scientists studied the processes of kinematics. Researches regarding this sphere of mechanics are still carried out. Practically, all physical phenomena are accompanied by movements of the body. In such a way, applications of kinematics can be found in different spheres.
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