ch1 - l . l 1 . 2 1 . 3 1.4 1 . 5 t . 6 I Introduction Whot...

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Unformatted text preview: l . l 1 . 2 1 . 3 1.4 1 . 5 t . 6 I Introduction Whot ls Mechqnics? Fundqmentol Concepts ond Principles Systems of Units Conversion from One System of Units to Another Method of Problem Solution Numericql Accurocy I .I WHAT 15 MECHANICS? Mechanics can be defined as that science which describes and predicts the conditions of rest or motion of bodies under the action of firces. It is divided into three parts: mechanics of rigid bodies, mechanics of deformablebodi,es, ani mechanics of Jtuids. The mechanics of riqid bodies is subdivided into statics and dynamics, t}e former dealing with bodies at rest, the latter with bodies in motion. In this part of the study of mechanics, bodies are assumed to be perfectly rigid. Actual structures and machines, however, are never absolutely rigid and deform under the loads to which they are subjected. But these deformations are usually small and do not appre- ciably affect the conditions of equilibrium or motion of the structure under consideration. They are important, though, as far as the resis- tance of the structure to failure is concerned and are studied in mechanics of materials, whlch is apart of the mechanics of deformable bodies. The third division of mechanics, the mechanics of fluids, is subdivided into the study of i,ncompressible fluids and of compressible fluids. An important subdivision of the study of incompressible fluids is hydraulics. which deals with problems involving water. Mechanics is a physical science, since it deals with the study of physical phenomena. However, some associate mechanics with math- ematics, while many consider it as an engineering subject. Both these views are justi{ied in part. Mechanics is the foundation of most engi- neering sciences and is an indispensable prerequisite to their study, However, it does not have the empiricisrz found in some engineering sciences, i.e., it does not rely on experience or observation alone; by its rigor and the emphasis it places on deductive reasoning it resembles mathematics. But, again, it is not an abstract or even apure science; mechanics is anapplied science. The pu{pose of mechanics is to explain and predict physical phenomena and thus to lay the foundations for engineering applications. 1.2 FUNDAMENTAT CONCEPTS AND PRINCIPTES Although the study of mechanics goes back to the time of Aristotle (384-322 e.c.) and Archimedes (287-212 n.c.), one has to wait until Newton (1642-1727) to find a satisfactory formulation of its funda- mental principles. These principles were later expressed in a modi- fied form by d'Alembert, Lagrange, and Hamilton. Their validity remained unchallenged, however, until Einstein formulated histheory of relatiaity (1905). While its limitations have now been recognized, nerptonian mechanics still remains the basis of todays engineering sciences....
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ch1 - l . l 1 . 2 1 . 3 1.4 1 . 5 t . 6 I Introduction Whot...

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