Engineering Dynamics

The subject of dynamics is an interdisciplinary blend of physics, applied mathematics, computational methods, and basic logic. The least difficult aspect of the subject is the basic physical laws, most of which are at least a century old. A primary element that has moved the study of dynamics from natural philosophy to engineering is the development of powerful tools for describing motion and for solving equations of motion. Throughout my career I have operated under the premise that the world is complicated,
and that a good text should prepare the student to address these complications. One of the methods I use here to meet this imperative is to provide examples that carefully guide the reader from the inception of a solution to its conclusion. I have tried to select examples that have most of the elements one might encounter in practice but are not so intricate as to mask the tautological features of the solution. An important feature of these examples is that the question of why a solution is assembled in a certain manner is regarded to be as important as the actual steps. In many cases I have used the same system to illustrate alternative approaches or different topics, which tends to give the treatment of those systems some of the aspects of the case study approach. Kinematics is the framework supporting the laws of dynamics. Being comfortable with the former vastly aids one to address the various kinetics concepts. For this reason a thorough treatment of the kinematics of particle and rigid-body motion is the focus of the initial development. The development is broad without going into specialized concepts that are primarily used in a confined topical area. The treatment in Chapter 2 of the kinematics of particle motion now derives the basic formulas for cylindrical and spherical coordinates prior to the tensor-oriented derivation of the comparable formulas for arbitrary orthogonal coordinate systems. This enables one to omit the more mathematical derivation without sacrificing fundamental concepts. An item of particular note is the expanded exploration in Chapter 3 of displacement of points relative to various reference frames, which should clarify many of the problematic aspects of the description of relative motion. I have found that it significantly assists students who are not practiced in visualizing spatial motion, and students in computer-aided design have told me that it aided them greatly in that subject. More important, the treatment leads to a derivation of the kinematics equations for relative motion that is simultaneously elegant and intuitive—there should be no misunderstanding of the significance of the various
terms. Chapter 4 addresses the kinematics of systems that are subject to kinematical constraints, with an emphasis on linkages and rolling. The modifications here relative
to the previous text are mostly incremental, but greater emphasis is now placed on the parallelism of the analysis of displacement, velocity, and acceleration. The example of a
cardan joint should be enlightening in this regard.

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