Translations of Encyclopedia about Physics

Basic Concepts of Mechanics

The word mechanics is derived from a Greek word which means something to the degree of "trade art". Mechanics is the oldest branch of physics and whose basic concepts were studied by scholars in ancient times. Mechanics studies the movement of objects and the forces which work on them. In a broader sense of the word, classical mechanics covers such concepts as inertia and gravity, weight, speed, density, and even the structure of material.

In the 20^th century, quantum mechanics came into existence and studied substances on their atomic and molecular levels. Relativity mechanics, formulated by Einstein, also came into existence. However, to this degree, classical mechanics did not become any less valid but rather became more limited to the extent it was applicable. When an object is of sufficient size, such as when it is visible when looking out the window, and does not move at a very fast speed but rather moves much slower than the speed of light, the laws of classical mechanics is sufficient to describe and explain physical phenomena.

Classical mechanics is made up of three components:

Statics concerns objects in a static state and studies the balance of forces which work on those objects in their static, calm state. Electrostatics studies deformations caused by forces acting on certain objects.

Kinematics describes the geometrical and mathematical components of an object’s movement without considering the forces applied to it.

For example, speed would be defined as the time it takes an object to travel along a certain path and is explained in m/s (metres per second) or km/hr (kilometres per hour). An example of kinematics is the description of a car’s speed during a certain time period without considering what may have caused the car to move in the first place.

Dynamics concerns the sum of forces and the changes they cause in the movement of a particular object.

If the forces acting on a particular object are not balanced, the object’s speed or direction of movement changes. Isaac Newton defined the laws of movement. According to these laws, if we would like to move an object of greater weight, we would require a greater force. From this we may conclude that objects with greater weight also have a larger inertia.

The weight of a particular object relates to the amount of matter found in it and is used to calculate the object’s inertia. Weight is most often defined in kilograms. Gravitational force (the force of gravity) gives an object its weight and is stated in newtons (A).

Thanks to the arrival of computer technology, our present knowledge of statics, kinematics and dynamics can be used to an immense degree. Every building and construction can be statically verified. Kinematics enables us to compile prognoses during the most complex of movements while dynamics, for example, performs a very important function when designing automobiles. During crash tests, forces applied to passengers at the moment of impact are studied in a similar fashion, helping designers to predict the probable outcome of their movement or reaction during an accident.

Therefore, our knowledge of classical mechanics applies today as it did yesterday, where the laws of mechanics were only applied to the present state and in response to the capabilities of technology. All mechanical solutions are aimed at understanding nature and using nature’s laws for our advantage.

Classical mechanics studies the composition of materials and tries to explain changes in density during changes in temperature, above all when a substance changes its solid, liquid or gaseous state.

All substances take up a particular space (volume). According to the particle model, each substance is made up of very small, indivisible particles which are in constant vibration and which carry energy. According to the discoverer of this phenomena, it is referred to as Braun’s movement of molecules.

If we add or remove energy from some substance (by cooling or heating it for example), the appearance of the formation of these particles changes. This appearance influences how the substance looks because density depends on the distance between the particles within it. The bonds between particles is stronger with solid substances than with liquids. When melting solid substances, the added energy loosens the structure of the particles within it, creating new and weaker bonds between the particles (cohesion) while, with the evaporation of liquids, the cohesion of particles breaks down totally. In this case, the volume of the substance is limited by its surroundings, such as by the size of some pot.

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