College Physics by Eugenia Etkina

Book Preface

To the student

College Physics is more than just a book. It’s a learning  companion. As a companion, the book won’t just tell you  about physics; it will act as a guide to help you build physics ideas using methods similar to those that practicing  scientists use to construct knowledge. The ideas that you  build will be yours, not just a copy of someone else’s ideas.  As a result, the ideas of physics will be much easier for  you to use when you need them: to succeed in your physics course, to obtain a good score on exams such as the  MCAT, and to apply to everyday life.

Although few, if any, textbooks can honestly claim to  be a pleasure to read, College Physics is designed to make  the process interesting and engaging. The physics you  learn in this book will help you understand many realworld phenomena, from why giant cruise ships are able to float to how telescopes work.

A great deal of research has been done over the past  few decades on how students learn. We, as teachers and  researchers, have been active participants in investigating the challenges students face in learning physics. We’ve  developed unique strategies that have proven effective in  helping students think like physicists. These strategies  are grounded in active learning, deliberate, purposeful  action on your part to learn something new. It’s not passively memorizing so that you can repeat it later. When  you learn actively you engage with the material. You relate  it to what you already know. You think about it in as many  different ways as you can. You ask yourself questions such  as “Why does this make sense?” and “Under what circumstances does this not apply?”

This book (your learning companion) includes many  tools to support the active learning process: each problemsolving strategies tool, worked example, observational  experiment, testing experiment, review question, and  end-of-chapter question and problem is designed to help  you build your understanding of physics. To get the most  out of these tools and the course, stay actively engaged in  the process of developing ideas and applying them. When  things get challenging, don’t give up.

At this point you should turn to the chapter Introducing Physics and begin reading. That’s where you’ll learn the details of the approach that the book uses, what physics  is, and how to be successful in the physics course you are  taking.

To the instructor

In writing College Physics, our main goal was to produce  an effective learning companion for students that incorporates results from the last few decades of physics education  research. This research has shown that there is a dramatic difference between how physicists construct new ideas and  how students traditionally learn physics. Students often  leave their physics course thinking of physics as a disconnected set of facts that has little to do with the real world,  rather than as a framework for understanding it.

To address this problem we have based this book on  a framework known as ISLE (Investigative Science Learning Environment) developed by authors Etkina and Van  Heuvelen. In ISLE, the construction of new ideas begins  with observational experiments. Students are explicitly  presented with simple experiments from which they discern patterns using available tools (diagrams, graphs, bar  charts, etc.). To explain the patterns, students devise explanations (hypotheses) for their observations. They then  use these explanations in testing experiments to make predictions about the outcomes of these new experiments. If  the prediction does not match the outcome of the experiment, the explanation needs to be reevaluated. Explanations that survive this testing process are the physics ideas  in which we then have more confidence.

The goal of this approach is to help students understand physics as a process by which knowledge of the natural world is constructed, rather than as a body of given  laws and facts. This approach also helps students reason  using the tools that physicists and physics educators have  developed for the analysis of phenomena—for example,  motion and force diagrams, kinematics and thermodynamics graphs, energy and momentum bar charts, and  many other visual representations. Using these tools helps  students bridge the gap between words and mathematical  equations. Along the way, they develop independent and  critical thinking skills that will allow them to build their  own understanding of physics principles.

All aspects of College Physics are grounded in ISLE  and physics education research. As a result, all of the features of the text have been designed to encourage students  to investigate, test ideas, and apply scientific reasoning.

Key learning principles

To achieve these goals we adhere to five key learning  principles:
1. Concept first, name second: The names we use for  physics concepts have everyday-life meanings that  may differ from the meanings they have when used  in physics. For example, in physics flux refers to the  amount to which a directed quantity (such as the  magnetic field) points through a surface, but in everyday-life flux refers to continuous change. Confu sion over the meaning of terms can get in the way of  learning. We address this difficulty by developing the  concept first and only then assigning a name to it.

2. Careful language: The vernacular physicists use is  rooted in history and tradition. While physicists have  an internal “dictionary” that lets them understand  the meaning of specific terms, students do not. We  are extremely careful to use language that promotes  understanding. For example: physicists would say that  “heat flows from a hot object to a cool object.” Heat  isn’t a substance that objects possess; heat is the flow  of energy. In this book we only use the word heat to  refer to the process of energy transfer.
3. Bridging words and mathematics: Words and mathematics are very abstract representations of physical  phenomena. We help students translate between these  abstractions by using concrete representations such as  force diagrams and energy bar charts as intermediate  steps.
4. Making sense of mathematics: We explicitly teach  students how to evaluate the results of their quantitative reasoning so they can have confidence in that  reasoning. We do this by building qualitative understanding first and then explicitly teaching students  how to use that understanding to check for quantitative consistency. We also guide students to use limiting cases to evaluate their results.
5. Moving away from plug-and-chug problem solving approaches: In this book you will find many  non-traditional examples and end-of-chapter problems that require students to use higher-level reasoning skills and not just plug numbers into equations  that have little meaning for them. Jeopardy problems  (where a solution is given and students must invent
a problem that leads to it), “tell-all” problems (where  students must determine everything possible), and  estimation problems (where students do not have  quantities given to them) are all designed to encourage higher reasoning and problem solving skills.

These key principles are described in greater detail  in the Introduction to the Instructor’s Guide that accompanies College Physics—please read that introduction. It  elaborates on the implementation of the methodology that  we use in this book and provides guidance on how to integrate the approach into your course.

While our philosophy informs College Physics, you  need not fully subscribe to it to use this textbook. We’ve  organized the book to fit the structure of most algebrabased physics courses: We begin with kinematics and  Newton’s laws, then move on to conserved quantities, statics, gases, fluids, thermodynamics, electricity and magnetism, vibrations and waves, optics, and finally modern  physics. The structure of each chapter will work with any  method of instruction. You can assign all of the innovative experimental tables and end-of-chapter problems, or  only a few. The text provides thorough treatment of fundamental principles, supplementing this coverage with  experimental evidence, new representations, an effective oach to problem solving, and interesting and motivating examples.

Brief Contents
I. Introducing Physics xxxiii
Part 1 Mechanics
1 Kinematics: Motion in One Dimension 2
2 Newtonian Mechanics 43
3 Applying Newton’s Laws 82
4 Circular Motion 120
5 Impulse and Linear Momentum 151
6 Work and Energy 184
7 Extended Bodies at Rest 229
8 Rotational Motion 274
Part 2  Gases and Liquids
9 Gases 318
10 Static Fluids 358
11 Fluids in Motion 390
Part 3  Thermodynamics
12 First Law of Thermodynamics 420
13 Second Law of Thermodynamics 461
Part 4 Electricity and Magnetism
14 Electric Charge, Force, and Energy 491
15 The Electric Field 531
16 DC Circuits 575
17 Magnetism 620
18 Electromagnetic Induction 661
Part 5 Vibrations and Wave s
19 Vibrational Motion 695
20 Mechanical Waves 734
21 Reflection and Refraction 775
22 Mirrors and Lenses 809
23 Wave Optics 851
24 Electromagnetic Waves 890
Part 6 Modern Physics
25 Special Relativity 922
26 Quantum Optics 959
27 Atomic Physics 997
28 Nuclear Physics 1041
29 Particle Physics 108