Tile changes occurring in the technological and social environments in which we<br >live are continuing at a rapid rate. In recent decades， advances in science and<br >engineering have made space travel possible， transformed our transportation<br >systems， revolutionized the practice of medicine， and miniaturized electronic<br >circuits so that a computer can be placed on a semiconductor chip. The list<br >of such achievements seems almost endless. In your science and engineering<br >courses， you will learn about some of the physical laws that underlie these<br >accomplishments.<br > The utilization of scientific and engineering knowledge for our benefit is<br >achieved through the design of things we use such as machines， structures，<br >products， and services. However， these achievements don t occur without a<br >price， monetary or otherwise. Therefore， the purpose of this book is to develop<br >and illustrate the principles and methodology required to answer the basic eco-<br >nomic question of any design: Do its benefits exceed its costs?<br > The Accreditation Board for Engineering and Technology states that engineer-<br >ing "is the profession in which a knowledge of the mathematical and natural<br >sciences gained by study， experience， and practice is applied with judgement to<br >develop ways to utilize， economically， the materials and forces of nature for the<br >benefit of mankind."* In this definition， the economic aspects of engineering as<br >well as the physical aspects are emphasized. Therefore， it is essential that the<br >economic part of engineering practice be accomplished effectivelv.<br >