Classical Mechanics

Mechanics is the branch of physical science that treats of the simplest form of motion of matter - mechanical motion. There are two types of mechanics: relativistic mechanics and classical mechanics. In their book, Yavorsky and Detlaf wrote: "Relativistic mechanics is the investigation of the motion of bodies traveling at velocities commensurate with the velocity of light". "Classical mechanics deals with the motions of bodies traveling at velocities that are very much less than the velocity of light in vacuum" (17). In this paper, I will just talk about classical mechanics. We often divide classical mechanics into six basic categories: kinematics of particles and rigid bodies, dynamics of translatory motion, work and mechanical energy, dynamics of rotary motion, fundamentals of analytical mechanics, and mechanical vibrations.

Kinematics of particles and rigid bodies deals with the problems of the internal structure of bodies, as well as the nature and laws of their interaction. Everybody agrees with Yavorsky and Detlaf that the mechanical motion "is made up of the changes in the relative positions of bodies, or their parts, in space in the course of time" (17). This category of classical mechanics helps a lot in case to make it clearly what is a rigid body. A rigid body is one body whose size and shape do not change when it is moving, because the distance between any two points in a rigid body remains constant over time. This explains why in this category, we study the mechanical motion of the body without regard for the interaction inside the body.

Dynamics of translatory motion deals with the influence of the interaction between bodies on their mechanical translatory motion. The most important parts of this category are Newton's three laws of motion. Newton's first law of motion states: "every material point persists in its state of rest or uniform in a straight line until the action of other bodies compels it to change that state" (Yavorsky and Detlaf 40). Newton's second law of motion states: "the first time derivative of the momenturn of a particle is equal to the force acting on it" (Yavorsky and Detlaf 47). Newton's third law of motion stated: "the actions of two particles on each other are equal in magnitude and opposite" (Yavorsky and Detlaf 49). With these three laws, physics determines what makes the motion of the body, how two bodies can interact with each other in motion.... Moreover, this category creates a lot of basic physics definitions, such as: mass, force, acceleration, gravitational field, etc.

Work and mechanical energy deals with work and mechanical energy. Mechanical energy is the energy- a common measure for various forms of motion - of the mechanical motion and interaction of bodies. "Work is done when a force pushes something and the object moves some distance in the direction it's being pushed" (Fowler). This category contains one of the most important and beautiful laws of nature: the law of conservation and conversion of energy. The law of conservation and conversion of energy states "the total energy remains constant in an isolated, or closed, system whatever the process occurring in the system"(Yavorsky and Detlaf 69). This law plays a very important and special part in physics. It is the only classical mechanics' law, which is also right in relativistic mechanics. It is the only theory that every scientist agrees is definitely right. We can say that the value of the work and mechanical energy category depends on this law: the law of conservation and conversion of energy!

Dynamics of rotary motion investigates rotational motion of objects and deals with effects that force has on motion. The most important thing in this category is Newton's second law for motion in angular form:
F * R = I * E
Where: F: force applied in plane of motion
R: radius distance of curvature of trajectory
I: moment of inertia of solid of mass m about axis located at distance l from its center of mass
E: angular acceleration vector
Scientists call this formula Newton's second law in angular form because this formulas has the property I - the moment of inertia. This property is actually the angular form of the property mass: "a measure of inertial and gravitational properties of body" (Yavorsky and Detlaf 44).

Fundamentals of analytical mechanics deal with the system as a whole rather than its individual components. This category is a different approach to the study of mechanics; while the other approach to the problems of mechanics, referred to as vectorial mechanics, were formulated for single particles and can be extended to systems of particles. There are a lot of definitions for the new physics terms that we do not have in Newton's mechanics. For example: the number of degrees of freedom of a system "coincides with the minimum number of independent coordinates necessary to describe the system uniquely " (Meirovitch 47).

Mechanical vibration of course deals with mechanical vibration. According to Jacob Hartog, vibration is "a periodic motion, a motion which repeats itself in all its particulars after a certain interval of time" (1). One example for mechanical vibration is the swinging of a pendulum. The motion repeats regularly. In life, mechanical vibration has more bad effects than good effects. The most serious effect of vibration, especially in the case of machinery, is that sufficiently high alternating stresses can produce fatigue failure in machine and structural parts. Less serious effects include increased wear of parts, general malfunctioning of apparatus, and the propagation of vibration through foundations and buildings to locations where the vibration of its acoustic realization is intolerable either for human comfort or for the successful operation of sensitive measuring equipment.

So, with those six basic categories: kinematics of particles and rigid bodies, dynamics of translatory motion, work and mechanical energy, dynamics of rotary motion, fundamentals of analytical mechanics, and mechanical vibrations; classical mechanics had built a very stable root for Physics. From classical mechanics, people have discovered relativistic mechanics, and from that people discover space, create spaceship, and open a new era for human life.

Works Cited:
Fowler, Michael. "Momentum, Work and Energy". Galileo and Einstein. 29, March 2007
Hartog, Jacob. Mechanical Vibrations. New York: Courier Dover Publications, 1985. 1-4
Meirovitch, Leonard. Methods of analytical dynamics. New York: Courier Dover Publications, 2004. 45-49
Nikitin. "Rotational Dynamics." Physics - help info. 25, March 2007 < http://physics-help.info/physicsguide/mechanics/rotational_dynamics.shtml >
Yavorsky and Detlaf. Handbook of Physics. Trans. Nicholas Weinstein. Moscow: Mir Publishers, 1975. 17-172.