Engineering Mechanics Dynamics Engineering Mechanics Volume 2 Dynamics Seventh Edition J. Kraige Virginia Polytechnic Institute and State University John Wiley & Sons, Inc. On the Cover: NASA and the European Space Agency are collaborating on the design of future missions which will gather samples of Martian surface material and return them to the earth. This artist’s view shows a spacecraft carrying a sample-retrieving rover and an ascent vehicle as it approaches Mars.
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Outside of the United States, please contact your local sales representative. 9780470614815 Printed in the United States of America 10 9 8 7 6 5 4 3 2 1 Foreword This series of textbooks was begun in 1951 by the late Dr. At that time, the books represented a revolutionary transformation in undergraduate mechanics education. They became the definitive textbooks for the decades that followed as well as models for other engineering mechanics texts that have subsequently appeared.
Published under slightly differ- ent titles prior to the 1978 First Editions, this textbook series has always been characterized by logical organization, clear and rigorous presentation of the theory, instructive sample prob- lems, and a rich collection of real-life problems, all with a high standard of illustration. In addi- tion to the U. versions, the books have appeared in SI versions and have been translated into many foreign languages. These texts collectively represent an international standard for un- dergraduate texts in mechanics.
The innovations and contributions of Dr. Meriam (1917–2000) to the field of engineer- ing mechanics cannot be overstated. He was one of the premier engineering educators of the second half of the twentieth century. Meriam earned his B.
degrees from Yale University. He had early industrial experience with Pratt and Whitney Aircraft and the General Electric Company. During the Second World War he served in the U. He was a member of the faculty of the University of California–Berkeley, Dean of Engineering at Duke University, a faculty member at the California Polytechnic State University–San Luis Obispo, and visiting professor at the University of California– Santa Barbara, finally retiring in 1990.
Professor Meriam always placed great emphasis on teaching, and this trait was recognized by his students wherever he taught. At Berkeley in 1963, he was the first recipient of the Outstanding Faculty Award of Tau Beta Pi, given pri- marily for excellence in teaching. In 1978, he received the Distinguished Educator Award for Outstanding Service to Engineering Mechanics Education from the American Society for Engineering Education, and in 1992 was the Society’s recipient of the Benjamin Garver Lamme Award, which is ASEE’s highest annual national award. Glenn Kraige, coauthor of the Engineering Mechanics series since the early 1980s, has also made significant contributions to mechanics education.
Kraige earned his B. degrees at the University of Virginia, principally in aerospace v vi Foreword engineering, and he currently serves as Professor of Engineering Science and Mechanics at Virginia Polytechnic Institute and State University. During the mid 1970s, I had the singular pleasure of chairing Professor Kraige’s graduate committee and take particular pride in the fact that he was the first of my forty-five Ph. Professor Kraige was invited by Professor Meriam to team with him and thereby ensure that the Meriam legacy of textbook authorship excellence was carried forward to future generations.
For the past three decades, this highly successful team of authors has made an enormous and global impact on the educa- tion of several generations of engineers. In addition to his widely recognized research and publications in the field of spacecraft dynamics, Professor Kraige has devoted his attention to the teaching of mechanics at both introductory and advanced levels. His outstanding teaching has been widely recognized and has earned him teaching awards at the departmental, college, university, state, regional, and national levels. These include the Francis J.
Maher Award for excellence in education in the Department of Engineering Science and Mechanics, the Wine Award for excellence in uni- versity teaching, and the Outstanding Educator Award from the State Council of Higher Ed- ucation for the Commonwealth of Virginia. In 1996, the Mechanics Division of ASEE bestowed upon him the Archie Higdon Distinguished Educator Award. The Carnegie Foun- dation for the Advancement of Teaching and the Council for Advancement and Support of Education awarded him the distinction of Virginia Professor of the Year for 1997. During 2004–2006, he held the W.
“Pete” White Chair for Innovation in Engineering Education, and in 2006 he teamed with Professors Scott L. Hendricks and Don H. Morris as recipients of the XCaliber Award for Teaching with Technology. In his teaching, Professor Kraige stresses the development of analytical capabilities along with the strengthening of physical insight and engineering judgment.
Since the early 1980s, he has worked on personal-computer software designed to enhance the teaching/learning process in statics, dynamics, strength of materials, and higher-level areas of dynamics and vibrations. The Seventh Edition of Engineering Mechanics continues the same high standards set by previous editions and adds new features of help and interest to students. It contains a vast collection of interesting and instructive problems. The faculty and students privileged to teach or study from Professors Meriam and Kraige’s Engineering Mechanics will benefit from the several decades of investment by two highly accomplished educators.
Following the pattern of the previous editions, this textbook stresses the application of theory to ac- tual engineering situations, and at this important task it remains the best. Junkins Distinguished Professor of Aerospace Engineering Holder of the George J. Eppright Chair Professorship in Engineering Texas A&M University College Station, Texas Preface Engineering mechanics is both a foundation and a framework for most of the branches of engineering. Many of the topics in such areas as civil, mechanical, aerospace, and agricul- tural engineering, and of course engineering mechanics itself, are based upon the subjects of statics and dynamics.
Even in a discipline such as electrical engineering, practitioners, in the course of considering the electrical components of a robotic device or a manufacturing process, may find themselves first having to deal with the mechanics involved. Thus, the engineering mechanics sequence is critical to the engineering curriculum. Not only is this sequence needed in itself, but courses in engineering mechanics also serve to solidify the student’s understanding of other important subjects, including applied math- ematics, physics, and graphics. In addition, these courses serve as excellent settings in which to strengthen problem-solving abilities.
Philosophy The primary purpose of the study of engineering mechanics is to develop the capacity to predict the effects of force and motion while carrying out the creative design functions of engineering. This capacity requires more than a mere knowledge of the physical and mathematical principles of mechanics; also required is the ability to visualize physical config- urations in terms of real materials, actual constraints, and the practical limitations which govern the behavior of machines and structures. One of the primary objectives in a mechan- ics course is to help the student develop this ability to visualize, which is so vital to problem formulation. Indeed, the construction of a meaningful mathematical model is often a more important experience than its solution.
Maximum progress is made when the principles and their limitations are learned together within the context of engineering application. There is a frequent tendency in the presentation of mechanics to use problems mainly as a vehicle to illustrate theory rather than to develop theory for the purpose of solving prob- lems. When the first view is allowed to predominate, problems tend to become overly idealized vii viii Preface and unrelated to engineering with the result that the exercise becomes dull, academic, and uninteresting. This approach deprives the student of valuable experience in formulating problems and thus of discovering the need for and meaning of theory.
The second view pro- vides by far the stronger motive for learning theory and leads to a better balance between theory and application. The crucial role played by interest and purpose in providing the strongest possible motive for learning cannot be overemphasized. Furthermore, as mechanics educators, we should stress the understanding that, at best, theory can only approximate the real world of mechanics rather than the view that the real world approximates the theory. This difference in philosophy is indeed basic and distinguishes the engineering of mechanics from the science of mechanics.
Over the past several decades, several unfortunate tendencies have occurred in engineer- ing education. First, emphasis on the geometric and physical meanings of prerequisite mathe- matics appears to have diminished. Second, there has been a significant reduction and even elimination of instruction in graphics, which in the past enhanced the visualization and repre- sentation of mechanics problems. Third, in advancing the mathematical level of our treat- ment of mechanics, there has been a tendency to allow the notational manipulation of vector operations to mask or replace geometric visualization.
Mechanics is inherently a subject which depends on geometric and physical perception, and we should increase our efforts to develop this ability. A special note on the use of computers is in order. The experience of formulating problems, where reason and judgment are developed, is vastly more important for the student than is the manipulative exercise in carrying out the solution.
