One of the fundamental branches of physics is mechanics – a discipline that studies the laws according to which the movement of bodies occurs, as well as the change in the parameters of movement as a result of the influence of bodies on each other.
The main areas of mechanics are the study of dynamics, kinematics and statics. Experts devote their entire lives to a detailed study of these sciences, since their provisions underlie the most important general engineering disciplines – the theory of mechanisms, resistance to materials, machine parts, etc.
What does theoretical mechanics study?
The movement and interaction of physical bodies are subject to strict laws according to which our Universe exists. Mechanics is devoted to the description and substantiation of these laws – a branch of physics that allows you to calculate and predict the motion of physical bodies, based on their main parameters and the forces acting on these bodies. Ideal objects are considered in mechanics:
- material point – an object, the main characteristic of which is mass, but dimensions are not taken into account;
- an absolutely solid body – a certain volume filled with a substance, the shape of which does not change under any influences, and the same distance is always maintained between any two points inside this volume;
- continuous deformable medium – the state of matter in a finite volume or in an unlimited space, in which the distances between arbitrary points can change as a result of external influences.
Mechanics considers the laws of motion when, over time, either the position of one body relative to another, or the relative position of parts of one body, changes. Time, mass and distance are basic values for mechanics.
The section of mechanics that studies the laws of motion, its geometric properties, the laws of speeds and accelerations, is called kinematics. The name of the discipline is derived from the Greek word “Κινειν”meaning movement. Kinematics studies pure motion from the point of view of space and time, without taking into account the masses of physical bodies and the forces acting on them.
Motion in kinematics is described exclusively by mathematical means, for which algebraic and geometric methods, calculus, etc. are used. At the same time, in classical kinematics, the reasons for the mechanical movement of bodies are not considered, and the characteristics inherent in the movement are considered absolute, i.e. they are not affected by the choice of the frame of reference. In addition to the classical one, there is relativistic mechanics, which considers the general concept of space-time with invariant intervals.
Another section of mechanics, which considers the causes that give rise to the mechanical movement of bodies, is called dynamics. This name is derived from the Greek word “Δύναμις”meaning strength. The basic concepts of dynamics are body mass, force acting on it, energy, momentum and angular momentum. The main tasks are to determine the force acting on a physical body, by the nature of its movement, and to determine the nature of the movement, based on the given forces of influence.
A significant contribution to the development of dynamics was made by the British scientist Isaac Newton, who formulated his three famous laws that describe the interaction of forces, and in fact became the ancestor of classical dynamics. This discipline studies the laws of motion at speeds limited by the interval from fractions of one millimeter per second to tens of kilometers per second. However, when considering the motion of ultra-small objects (elementary particles) and ultra-high speeds approaching the speed of light, the laws of classical dynamics cease to apply.
The laws of the stay of bodies and systems in equilibrium when various forces and moments are applied to them, statics is another direction of mechanics. The name of the discipline comes from the Greek word “Στατός”meaning immobility. For statics, six axioms are formulated that describe the conditions for finding a body or a system of physical bodies in a state of equilibrium, as well as two consequences of these axioms.
The main object in statics is a body or a material point in a state of equilibrium, i.e. motionless or moves in the considered inertial coordinate system uniformly and along a straight line. The limiting factors for a body in balance are external forces that act on it, as well as other bodies called bonds.