Physics , Second Edition

Book Preface

Physics is intended for a two-semester college course in introductory physics using algebra and trigonometry. Our main goals in writing this book are

• to present the basic concepts of physics that students need to know for later courses and future careers,
• to emphasize that physics is a tool for understanding the real world, and
• to teach transferable problem-solving skills that students can use throughout their lives.

We have kept these goals in mind while developing the main themes of the book.

NEW TO THIS EDITION

Although the fundamental philosophy of the book has not changed, detailed feedback from almost 60 reviewers (many of whom used the first edition in the classroom) has enabled us to fine-tune our approach to make the text even more user-friendly, concep-tually based, and relevant for students. The second edition also has some added features to further facilitate student learning.

A greater emphasis has been placed on fundamental physics concepts:

• Connections identify areas in each chapter where important concepts are revisited. A marginal Connections heading and summary adjacent to the coverage in the main text help students easily recognize that a previously introduced concept is being applied to the current discussion. Knowledge is being revisited and further developed—not newly introduced.
• Checkpoint questions have been added to applicable sections of the text to allow students to pause and test their understanding of the concept explored within the current section. The answers to the Checkpoints are found at the end of the chapter so that students can confirm their knowledge without jumping too quickly to the provided answer.
• The exercises in the Review & Synthesis sections have been revised to concentrate even more heavily on helping students to realize through practice problems how the concepts in the previously covered group of chapters are interrelated. The number of problems in the Review & Synthesis sections has also been increased in the new edition. (The MCAT review problems have been retained to also help pre-med students focus on the concepts covered in the upcoming exam.)
• Nonessential coverage and derivations have been moved to the text’s website. This will help students not only to focus further on the fundamental, core concepts in their reading of the text but also allow them to go online for additional informa-tion or explanation on topics of interest. identifiers in the text direct students to additional information online.

In addition, the following general revisions occur in chapters of the text:

• The topical question from the chapter-opening vignette now appears in the margin (along with a reduced version of the chapter-opening image) to help students iden-tify where in the main text the answer to the chapter-opening question is addressed.
• Applications have been clearly identified as such in the text with a complete listing in the front matter.
• Many helpful subheadings have been added to the text to help students quickly identify new subtopics.
• Portions of the text now caption images to establish a visual connection between the text’s concepts and terms and the art and photos.

• Great care was taken by both the authors and the contributors to the second edition to revise the end-of-chapter and Review & Synthesis problems. Approximately 150 problems are new, and an emphasis has been placed on progressing difficulty level to help students gain confidence and reinforce new skills before tackling more challenging problems.
The following lists major chapter-specific revisions to the text:

Chapter 2: Vector notation has been removed from Chapter 2. Discussion of vectors and components of vectors now begins in Chapter 3.
Chapter 3: A discussion of Unit Vectors has been added to Section 3.2. A new example for finding average velocity has been added.
Chapter 4: A more concise section on air resistance is provided with a more detailed discussion available online. A new Figure 4.20 emphasizes the normal and frictional forces as perpendicular components of a contact force.
Chapter 7 : Section 7.6 Motion of the Center of Mass has been simplified. Chapter 8 : Example 8.1 has been replaced with a new problem on the rotational inertia of a barbell.
Chapter 10: Section 10.8 The Pendulum has been made much more concise with a more detailed discussion of the physical pendulum available online.
Chapter 11 : A new “law box” highlights the physical properties that determine wave speed. The discussion on interference has been expanded for added clarity.
Chapter 12 : In Section 12.9, the discussion of shock waves has been shortened. A more detailed discussion is available online.
Chapter 14 : A detailed discussion of convection and Example 14.12 Roller Blading in Still Air have been moved online. Section 14.7 is now a brief, conceptual description of convection. Section 14.8 Thermal Radiation has been revised with a clearer descrip-tion of solar radiation and global warming.
Chapter 15 : Section 15.5 Heat Engines has been revised to include a more accurate description of the development of the steam engine. The process of the internal combus-tion engine is now illustrated in Figure 15.12. Details of the Carnot cycle and discussion of the statistical interpretation of entropy are available online.
Chapter 16 : A new Example 16.7 Electric Field due to Three Point Charges has been added.
Chapter 22 : Section 22.1 has been simplified and is now titled Maxwell’s Equations and Electromagnetic Waves. A more detailed discussion appears online. The material on antennas has been made more concise.
Chapter 27 : The derivation of the radii of the Bohr orbits has been moved online. The section on atomic energy levels has been revised and made more concise.
Chapter 28 : Section 28.8 Electron Energy Levels in a Solid has been made much more concise with a more detailed discussion available online.
Chapter 30 : The discussions of quarks and leptons have been expanded and clari-fied. The discussion of the standard model is significantly more concise. Twenty-first-century particle physics has been updated, and the most recent information will be provided online.
Please see your McGraw-Hill sales representative for a more detailed list of revisions.

ORGANIZATION OF CHAPTERS 2 THROUGH 4

In spite of the more traditional organization, Chapters 2–4 retain much of the flavor of the approach in College Physics. In particular, we use correct vector notation, diagrams, terminology, and methods from the very beginning. For example, we care-fully distinguish components from magnitudes by writing “vx = −5 m/s” and never “v = −5 m/s,” even if the object moves only along the x-axis.

COMPREHENSIVE COVERAGE

Students should be able to get the whole story from the book. The text works well in our self-paced course, where students must rely on the textbook as their primary learning resource. Nonetheless, completeness and clarity are equally advantageous when the book is used in a more traditional classroom setting. Physics frees the instructor from having to try to “cover” everything. The instructor can then tailor class time to more important student needs—reinforcing difficult concepts, working through example problems, engaging the students in cooperative learning activities, describing applications, or presenting demonstrations.

INTEGRATING CONCEPTUAL PHYSICS INTO A QUANTITATIVE COURSE

Some students approach introductory physics with the idea that physics is just the memorization of a long list of equations and the ability to plug numbers into those equations. We want to help students see that a relatively small number of basic phys-ics concepts are applied to a wide variety of situations. Physics education research has shown that students do not automatically acquire conceptual understanding; the con-cepts must be explained and the students given a chance to grapple with them. Our presentation, based on years of teaching this course, blends conceptual understanding with analytical skills. The Conceptual Examples and Conceptual Practice Problems in the text and a variety of Conceptual and Multiple-Choice Questions at the end of each chapter give students a chance to check and to enhance their concep-tual understanding.

INTRODUCING CONCEPTS INTUITIVELY

We introduce key concepts and quantities in an informal way by establishing why the quantity is needed, why it is useful, and why it needs a precise definition. Then we make a transition from the informal, intuitive idea to a formal definition and name. Concepts motivated in this way are easier for students to grasp and remember than are concepts introduced by seemingly arbitrary, formal definitions.
For example, in Chapter 8, the idea of rotational inertia emerges in a natural way from the concept of rotational kinetic energy. Students can understand that a rotating rigid body has kinetic energy due to the motion of its particles. We discuss why it is use-ful to be able to write this kinetic energy in terms of a single quantity common to all the particles (the angular speed), rather than as a sum involving particles with many different speeds. When students understand why rotational inertia is defined the way it is, they are better prepared to move on to the concepts of torque and angular momentum.
We avoid presenting definitions or formulas without any motivation. When an equa-tion is not derived in the text, we at least describe where the equation comes from or give a plausibility argument. For example, Section 9.9 introduces Poiseuille’s law with two identical pipes in series to show why the volume flow rate must be proportional to the pressure drop per unit length. Then we discuss why Δ V /Δ t is proportional to the fourth power of the radius (rather than to r 2 , as it would be for an ideal fluid).

WRITTEN IN CLEAR AND FRIENDLY STYLE

We have kept the writing down-to-earth and conversational in tone—the kind of language an experienced teacher uses when sitting at a table working one-on-one with a student. We hope students will find the book pleasant to read, informative, and accurate without seeming threatening, and filled with analogies that make abstract concepts easier to grasp. We want students to feel confident that they can learn by studying the textbook.

While learning correct physics terminology is essential, we avoid all unnecessary jargon—terminology that just gets in the way of the student’s understanding. For example, we never use the term centripetal force, since its use sometimes leads students to add a spurious “centripetal force” to their free-body diagrams. Likewise, we use radial component of acceleration because it is less likely to introduce or reinforce mis-conceptions than centripetal acceleration.

ACCURACY ASSURANCE

The authors and the publisher acknowledge the fact that inaccuracies can be a source of frustration for both the instructor and students. Therefore, throughout the writing and production of this edition, we have worked diligently to eliminate errors and inaccura-cies. Bill Fellers of Fellers Math & Science conducted an independent accuracy check and worked all end-of-chapter questions and problems in the final draft of the manu-script. He then coordinated the resolution of discrepancies between accuracy checks, ensuring the accuracy of the text, the end-of-book answers, and the solutions manuals. Corrections were then made to the manuscript before it was typeset.
The page proofs of the text were double-proofread against the manuscript to ensure the correction of any errors introduced when the manuscript was typeset. The textual examples, practice problems and solutions, end-of-chapter questions and problems, and problem answers were accuracy checked by Fellers Math & Science again at the page proof stage after the manuscript was typeset. This last round of corrections was then cross-checked against the solutions manuals.