Principles & practice of physics

1845 Pages·2015·222.842 MB·English

by  Eric Mazur, Daryl Pedigo

SI Units, Useful Data, and
Unit Conversion Factors
The seven base SI units
Unit Abbreviation Physical quantity
meter m length  
kilogram kg mass  
second s time  
ampere A electric current  
kelvin K thermodynamic temperature  
mole mol amount of substance  
candela cd luminous intensity  
Some derived SI units  
Unit Abbreviation Physical quantity In terms of base units
newton N force kg#m s2
joule J energy kg#m2>s2
watt W power kg#m2>s3
pascal Pa pressure kg m#>s2
hertz Hz frequency s-1>
#
coulomb C electric charge A s
volt V electric potential kg#m2 (A#s3)
ohm Ω electric resistance kg#m2>(A2#s3)
farad F capacitance A2#s4 (>kg#m2)
tesla T magnetic field kg (A>#s2)
weber Wb magnetic flux kg>#m2 (A#s2)
henry H inductance kg#m2>(A2#s2)
>
SI Prefixes
10n Prefix Abbreviation 10n Prefix Abbreviation
100 — —      
103 kilo- k 10-3 milli- m
106 mega- M 10-6 micro- m
109 giga- G 10-9 nano- n
1012 tera- T 10-12 pico- p
1015 peta- P 10-15 femto- f
1018 exa- E 10-18 atto- a
1021 zetta- Z 10-21 zepto- z
1024 yotta- Y 10-24 yocto- y
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Values of fundamental constants
Quantity Symbol Value
Speed of light in vacuum c0 3.00×108 m s
Gravitational constant G 6.6738×10-1>1 N#m2 kg2
>
Avogadro’s number NA 6.0221413×1023 mol-1
Boltzmann’s constant kB 1.380×10-23 J K
>
Charge on electron e 1.60×10-19 C
Permittivity constant P0 8.85418782×10-12 C2 (N#m2)
Permeability constant m0 4p×10-7 T#m A >
Planck’s constant h 6.626×10-34 J#>s
Electron mass me 9.11×10-31 kg
Proton mass mp 1.6726×10-27 kg
Neutron mass mn 1.6749×10-27 kg
Atomic mass unit amu 1.6605×10-27 kg
Other useful numbers
Number or quantity Value
p 3.1415927
e 2.7182818
1 radian 57.2957795°
Absolute zero (T=0) -273.15 °C
Average acceleration g due to gravity near Earth’s 9.8 m s2
surface
>
Speed of sound in air at 20 °C 343 m s
>
Density of dry air at atmospheric pressure and 20 °C 1.29 kg m3
>
Earth’s mass 5.97×1024 kg
Earth’s radius (mean) 6.38×106 m
Earth–Moon distance (mean) 3.84×108 m
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PRINCIPLES & PRACTICE OF
P H Y S I C S
E R I C M A Z U R
PrinciPles & Practice of
P h y s i c s
Eric Mazur
Harvard University
With contributions from
Catherine H. Crouch
Swarthmore College
Peter A. Dourmashkin
Massachusetts Institute of Technology
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Credits and acknowledgments borrowed from other sources and reproduced, with permis-
sion, in this textbook appear on the appropriate page within the text or on p. C-1.
Copyright ©2015 Pearson Education, Inc. All rights reserved. Manufactured in the United
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Brief Contents
Volume 1 of Principles of Physics includes Chapters 1–21. Volume 2 of Principles of Physics includes Chapters 22–34.
Chapter 1 Foundations 1
Chapter 2 Motion in One Dimension 28
Chapter 3 Acceleration 53
Chapter 4 Momentum 75
Chapter 5 Energy 101
Chapter 6 Principle of Relativity 121
Chapter 7 Interactions 148
Chapter 8 Force 176
Chapter 9 Work 202
Chapter 10 Motion in a Plane 226
Chapter 11 Motion in a Circle 254
Chapter 12 Torque 281
Chapter 13 Gravity 308
Chapter 14 Special Relativity 337
Chapter 15 Periodic Motion 374
Chapter 16 Waves in One Dimension 400
Chapter 17 Waves in Two and Three Dimensions 432
Chapter 18 Fluids 463
Chapter 19 Entropy 501
Chapter 20 Energy Transferred Thermally 530
Chapter 21 Degradation of Energy 562
Chapter 22 Electric Interactions 593
Chapter 23 The Electric Field 615
Chapter 24 Gauss’s Law 639
Chapter 25 Work and Energy in Electrostatics 663
Chapter 26 Charge Separation and Storage 685
Chapter 27 Magnetic Interactions 710
Chapter 28 Magnetic Fields of Charged Particles in Motion 735
Chapter 29 Changing Magnetic Fields 759
Chapter 30 Changing Electric Fields 781
Chapter 31 Electric Circuits 811
Chapter 32 Electronics 842
Chapter 33 Ray Optics 875
Chapter 34 Wave and Particle Optics 908
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About the Author
Eric Mazur is the Balkanski Professor of Physics and Applied Physics at
harvard University and Area Dean of Applied Physics. Dr. Mazur is a
renowned scientist and researcher in optical physics and in education
research, and a sought-after author and speaker.
Dr. Mazur joined the faculty at harvard shortly after obtaining his Ph.D. at the
University of Leiden in the Netherlands. in 2012 he was awarded an honorary
Doctorate from the École Polytechnique and the University of Montreal. he is
a Member of the Royal Academy of sciences of the Netherlands and holds
honorary professorships at the institute of semiconductor Physics of the chinese
Academy of sciences in Beijing, the institute of Laser Engineering at the Beijing
University of Technology, and the Beijing Normal University.
Dr. Mazur has held appointments as Visiting Professor or Distinguished
Lecturer at carnegie Mellon University, the Ohio state University, the Pennsylvania
state University, Princeton University, Vanderbilt University, hong Kong University,
the University of Leuven in Belgium, and National Taiwan University in Taiwan,
among others.
in addition to his work in optical physics, Dr. Mazur is interested in education,
science policy, outreach, and the public perception of science. in 1990 he began
developing peer instruction, a method for teaching large lecture classes interac-
tively. This teaching method has developed a large following, both nationally and
internationally, and has been adopted across many science disciplines.
Dr. Mazur is author or co-author of over 250 scientific publications and holds
two dozen patents. he has also written on education and is the author of Peer
Instruction: A User’s Manual (Pearson, 1997), a book that explains how to teach
large lecture classes interactively. in 2006 he helped produce the award-winning
DVD Interactive Teaching. he is the co-founder of Learning catalytics, a p latform
for promoting interactive problem solving in the classroom, which is available in
MasteringPhysics®.
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To the Student
Let me tell you a bit about myself. others to see the beauty of the universe—is a wonderful
i always knew exactly what i wanted to do. it just never combination.
worked out that way. When i started teaching, i did what all teachers did at the
When i was seven years old, my grandfather gave me time: lecture. it took almost a decade to discover that my
a book about astronomy. Growing up in the Netherlands award-winning lecturing did for my students exactly what
i became fascinated by the structure of the solar system, the courses i took in college had done for me: it turned the
the Milky Way, the universe. i remember struggling with subject that i was teaching into a collection of facts that my
the concept of infinite space and asking endless questions students memorized by rote. instead of transmitting the
without getting satisfactory answers. i developed an early beauty of my field, i was essentially regurgitating facts to
passion for space and space exploration. i knew i was going my students.
to be an astronomer. in high school i was good at physics, When i discovered that my students were not master-
but when i entered university and had to choose a major, ing even the most basic principles, i decided to completely
i chose astronomy. change my approach to teaching. instead of lecturing, i
it took only a few months for my romance with the heav- asked students to read my lecture notes at home, and then,
ens to unravel. instead of teaching me about the mysteries in class, i taught by questioning—by asking my students to
and structure of the universe, astronomy had been reduced reflect on concepts, discuss in pairs, and experience their
to a mind-numbing web of facts, from declinations and own “aha!” moments.
right ascensions to semi-major axes and eccentricities. Dis- Over the course of more than twenty years, the lecture
illusioned about astronomy, i switched majors to physics. notes have evolved into this book. consider this book to be
Physics initially turned out to be no better than astronomy, my best possible “lecturing” to you. But instead of listening
and i struggled to remain engaged. i managed to make it to me without having the opportunity to reflect and think,
through my courses, often by rote memorization, but the this book will permit you to pause and think; to hopefully
beauty of science eluded me. experience many “aha!” moments on your own.
it wasn’t until doing research in graduate school that i re- i hope this book will help you develop the thinking skills
discovered the beauty of science. i knew one thing for sure, that will make you successful in your career. And remem-
though: i was never going to be an academic. i was going ber: your future may be—and likely will be—very different
to do something useful in my life. Just before obtaining my from what you imagine.
doctorate, i lined up my dream job working on the develop- i welcome any feedback you have. Feel free to send me
ment of the compact disc, but i decided to spend one year email or tweets.
doing postdoctoral research first. i wrote this book for you.
it was a long year. After my postdoc, i accepted a junior Eric Mazur
faculty position and started teaching. That’s when i discov- @eric_mazur
ered that the combination of doing research—uncovering [email protected]
the mysteries of the universe—and teaching—helping cambridge, MA
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To the Instructor
They say that the person who teaches is the one who Setting a new standard
learns the most in the classroom. indeed, teaching led me
The tenacity of the standard approach in textbooks can be
to many unexpected insights. so, also, with the writing
attributed to a combination of inertia and familiarity. Teach-
of this book, which has been a formidably exciting intel-
ing large introductory courses is a major chore, and once a
lectual journey.
course is developed, changing it is not easy. Furthermore,
the standard texts worked for us, so it’s natural to feel that
Why write a new physics text? they should work for our students, too.
The fallacy in the latter line of reasoning is now well-
in May 1993 i was driving to Troy, Ny, to speak at a meeting
known thanks to education research. Very few of our stu-
held in honor of Robert Resnick’s retirement. in the car with
dents are like us at all. Most take physics because they are
me was a dear friend and colleague, Albert Altman, professor
required to do so; many will take no physics beyond the
at the University of Massachusetts, Lowell. he asked me if i
introductory course. Physics education research makes it
was familiar with the approach to physics taken by Ernst Mach
clear that the standard approach fails these students.
in his popular lectures. i wasn’t. Mach treats conservation of
Because of pressure on physics departments to deliver
momentum before discussing the laws of motion, and his for-
better education to non-majors, changes are occurring in
mulation of mechanics had a profound influence on Einstein.
the way physics is taught. These changes, in turn, create a
The idea of using conservation principles derived from
need for a textbook that embodies a new educational phi-
experimental observations as the basis for a text—rather
losophy in both format and presentation.
than Newton’s laws and the concept of force—appealed to
me immediately. After all, most physicists never use the
concept of force because it relates only to mechanics. it has Organization of this book
no role in quantum physics, for example. The conservation
As i considered the best way to convey the conceptual
principles, however, hold throughout all of physics. in that
framework of mechanics, it became clear that the standard
sense they are much more fundamental than Newton’s laws.
curriculum truly deserved to be rethought. For example, stan-
Furthermore, conservation principles involve only algebra,
dard texts are forced to redefine certain concepts more than
whereas Newton’s second law is a differential equation.
once—a strategy that we know befuddles students. ( Examples
it occurred to me, however, that Mach’s approach could be
are work, the standard definition of which is incompatible
taken further. Wouldn’t it be nice to start with conservation of
with the first law of thermodynamics, and energy, which is
both momentum and energy, and only later bring in the con-
redefined when modern physics is discussed.)
cept of force? After all, physics education research has shown
Another point that has always bothered me is the arbi-
that the concept of force is fraught with pitfalls. What’s more,
trary division between “modern” and “classical” physics.
after tediously deriving many results using kinematics and
in most texts, the first thirty-odd chapters present physics
dynamics, most physics textbooks show that you can derive
essentially as it was known at the end of the 19th century;
the same results from conservation principles in just one or
“modern physics” gets tacked on at the end. There’s no need
two lines. Why not do it the easy way first?
for this separation. Our goal should be to explain physics in
it took me many years to reorganize introductory phys-
the way that works best for students, using our full contem-
ics around the conservation principles, but the resulting ap-
porary understanding. All physics is modern!
proach is one that is much more unified and modern—the
That is why my table of contents departs from the “standard
conservation principles are the theme that runs throughout
organization” in the following specific ways.
this entire book.
Additional motives for writing this text came from my own Emphasis on conservation laws. As mentioned earlier, this
teaching. Most textbooks focus on the acquisition of infor- book introduces the conservation laws early and treats them
mation and on the development of procedural knowledge. the way they should be: as the backbone of physics. The ad-
This focus comes at the expense of conceptual understand- vantages of this shift are many. First, it avoids many of the
ing or the ability to transfer knowledge to a new context. As standard pitfalls related to the concept of force, and it leads
explained below, i have structured this text to redress that naturally to the two-body character of forces and the laws
balance. i also have drawn deeply on the results of physics of motion. second, the conservation laws enable students
education research, including that of my own research group. to solve a wide variety of problems without any calculus.
i have written this text to be accessible and easy for stu- indeed, for complex systems, the conservation laws are often
dents to understand. My hope is that it can take on the the natural (or only) way to solve problems. Third, the book
burden of basic teaching, freeing class time for synthesis, deduces the conservation laws from observations, helping
discussion, and problem solving. to make clear their connection with the world around us.
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