Each of the seven parts of this book opens with an overview to give you a look ahead, a glimpse at where your journey will take you in the next few chapters. It’s easy to lose sight of the big picture while you’re busy negotiating the terrain of each chapter. In addition, each part closes with a Knowledge Structure to help you consolidate your knowledge. You might want to look ahead now to the Part I Knowledge Structure .

In Part I, the big picture, in a word, is motion.

• How do we describe motion? It is easy to say that an object moves, but it’s not obvious how we should measure or characterize the motion if we want to analyze it mathematically. The mathematical description of motion is called kinematics, and it is the subject matter of Chapters 1 through 4.

• How do we explain motion? Why do objects have the particular motion they do? Why, when you toss a ball upward, does it go up and then come back down rather than keep going up? What “laws of nature” allow us to predict an object’s motion? The explanation of motion in terms of its causes is called dynamics, and it is the topic of Chapters 5 through 8.

Two key ideas for answering these questions are force (the “cause”) and acceleration (the “effect”). A variety of pictorial and graphical tools will be developed in Chapters 1 through 5 to help you develop an intuition for the connection between force and acceleration. You’ll then put this knowledge to use in Chapters 5 through 8 as you analyze motion of increasing complexity.

Another important tool will be the use of models. Reality is extremely complicated. We would never be able to develop a science if we had to keep track of every little detail of every situation. A model is a simplified description of reality—much as a model airplane is a simplified version of a real airplane—used to reduce the complexity of a problem to the point where it can be analyzed and understood. We will introduce several important models of motion, paying close attention, especially in these earlier chapters, to where simplifying assumptions are being made, and why.

The laws of motion were discovered by Isaac Newton roughly 350 years ago, so the study of motion is hardly cutting-edge science. Nonetheless, it is still extremely important. Mechanics—the science of motion—is the basis for much of engineering and applied science, and many of the ideas introduced here will be needed later to understand things like the motion of waves and the motion of electrons through circuits. Newton’s mechanics is the foundation of much of contemporary science, thus we will start at the beginning.