This book, "Energy Principles and Variational Methods in Applied Mechanics" by J. N. Reddy, is intended for senior undergraduate and beginning graduate students in aerospace, civil, and mechanical engineering, as well as applied mechanics. It provides an introduction to energy principles and variational methods, which are essential in the formulation and solution of mechanics problems. The book is organized into 10 chapters, each covering different aspects of energy principles and variational methods. Chapter 1 introduces variational principles, while Chapter 2 reviews vector and tensor algebra. Chapter 3 covers the basic equations of linear solid mechanics. Chapters 4 through 7 discuss work, energy, variational calculus, and classical variational methods of approximation. Chapter 8 applies these principles to plates, while Chapter 9 introduces the finite element method with applications to beams and plates. Chapter 10 discusses mixed variational principles for elasticity. Each chapter includes example problems, exercises, and references. The book is suitable as a textbook for a senior undergraduate or first-year graduate course on energy principles and variational methods. It is written for students who have completed basic courses in differential equations, mechanics of materials, and dynamics. The author thanks colleagues and students for their support and acknowledges the influence of Professor J. T. Oden and Professor C. W. Bert. The book also includes answers to selected exercises and a subject index. The content is comprehensive, covering both theoretical and practical aspects of energy principles and variational methods in applied mechanics.This book, "Energy Principles and Variational Methods in Applied Mechanics" by J. N. Reddy, is intended for senior undergraduate and beginning graduate students in aerospace, civil, and mechanical engineering, as well as applied mechanics. It provides an introduction to energy principles and variational methods, which are essential in the formulation and solution of mechanics problems. The book is organized into 10 chapters, each covering different aspects of energy principles and variational methods. Chapter 1 introduces variational principles, while Chapter 2 reviews vector and tensor algebra. Chapter 3 covers the basic equations of linear solid mechanics. Chapters 4 through 7 discuss work, energy, variational calculus, and classical variational methods of approximation. Chapter 8 applies these principles to plates, while Chapter 9 introduces the finite element method with applications to beams and plates. Chapter 10 discusses mixed variational principles for elasticity. Each chapter includes example problems, exercises, and references. The book is suitable as a textbook for a senior undergraduate or first-year graduate course on energy principles and variational methods. It is written for students who have completed basic courses in differential equations, mechanics of materials, and dynamics. The author thanks colleagues and students for their support and acknowledges the influence of Professor J. T. Oden and Professor C. W. Bert. The book also includes answers to selected exercises and a subject index. The content is comprehensive, covering both theoretical and practical aspects of energy principles and variational methods in applied mechanics.