Physics 141
Physics Department
Cal Poly
San Luis Obispo
The
Laws
of Motion, Forces, Energy, Momentum
and the Conservation Laws
It
is the
most persistent and greatest adventure in human history, this search to
understand
the universe, how it works and where it came from. It is difficult to
imagine
that a handful of residents of a small planet circling an insignificant
star in
a small galaxy have as their aim a complete understanding of the entire
universe, a small speck of creation truly believing it is capable of
comprehending the whole.

Murray GellMann, Caltech physicist
Last updated: March 28, 2014
General Physics: Mechanics
An introductory calculusbased course in classical mechanics  the
first course in the physics sequence. Topics
include
the description of motion, Newton's laws, the concepts of work and
energy,
impulse and momentum, and torque and angular momentum and the three
conservation laws (energy, momentum, and angular momentum) that
characterize
the motions of objects and the principles that govern their motion.
The course will meet four days per week  MTuWTh 5:106:00
 Science North Bldg 53213).
Instructor: Dr. Ron Brown  Physics
Department
Textbook:
PHYSICS
FOR SCIENTISTS AND ENGINEERS, 3rd Ed., by Randall
Knight, Pearson
(2012)
PHYSICS 141 Supplemental Notes and
Problems, by Ron Brown, El Corral (2008)
Course
Syllabus
Calendar
Physics 141 Topics
and Notes
Resources
Great Ideas that
Have
Changed Our Worldview  An essay
Physics
Central  A great link!
This course will deal with
the basic ideas
of forces and motion  its description and the
principles that govern it. The topics of the course include the
description of
motion, Newton's laws, the concepts of work and energy, impulse and
momentum,
torque and angular momentum  and the three conservation laws that
govern that
motion  and how to use those ideas and principles to solve problems.
But it
will also deal with much more. What you should gain from this course is
an understanding
of the way that science works  the critical method of how our ideas
about
nature are formulated. It is this that you will ultimately carry with
you long
after the specifics of the course have waned from your memory.
While studying how to solve problems
involving motions of objects, we
want to
also consider grand questions like: Why do things fall with the same
constant
acceleration (and do they always)? What IS gravity? What is the law of
gravity
that ultimately governs the motions of falling objects, the planets,
and the
stars and galaxies? How can we know the mass of the earth (and why
would we
want to)? Why are the planetary orbits elliptical? (And, by the way,
how
do we
even know that our planet is orbiting a small star 150 million
kilometers away,
anyway?) What
can we know  and on what can we merely speculate?
Science
is ultimately about ways of knowing  how we know
what we know.
RESOURCES:
 Textbook: PHYSICS FOR SCIENTISTS AND ENGINEERS,
3rd Ed., by Randall Knight
(Pearson, 2012)
Note: This is the 3rd edition of this
text. You will use the same book in
PHYS 132 and 133.
• Supplemental Notes: Physics
141
SUPPLEMENTAL NOTES AND PROBLEMS by
Ronald Brown (El Corral)
The supplemental notes
are intended to be used
along with the
text to relate the important ideas of the course.
The supplement should give you a
little different perspective and approach to the material of the
course. The order will be different than
the
text in places. It is recommended that you read both presentations
carefully. References will be made to both the text and the
supplemental notes throughout the course. The
supplement is
available in
El Corral with the physics textbooks.
The Supplement is about 100 pages
or so
covering
kinematics, Newton's laws, work and energy, momentum, and rotational
motion.
The notes are intended to support the text  and focus on the
fundamental
concepts, ideas, and principles related to each of the topics and on
tying the
principles together and leaving you with a strong conceptual
understanding.
Each section concludes with a set of conceptual questions and problems
to help
your study.
 References  Any
other introductory physics textbook. It is often very helpful to
read
the same ideas in different texts  so any other introductory text can
be a useful resource. In addition to the text material itself,
often
other books will have a different set of examples that you can follow
to strengthen your problem solving approach
 Office Hours  Make
good use of the access
you have to your
faculty in all courses. Don't wait until you are in trouble in a class
to seek
help. When you don't understand something, ask! If you just want to
discuss the
ideas or look for reassurance on your line of reasoning, make use of
office
hours. If you cannot get to office hours for some reason, contact me
after class or by email to set up a time to meet  or just
stop by my office.
 Private Tutoring 
Individual arrangements can be
made with Physics
majors available for tutoring in Sci. Bldg. room E25 (known
affectionately as
"hbar"  a physics injoke)
 DropIn Help  Those
same tutors will also usually help for free
if you just stop by "hbar" or go to the Learning Center.
 Physics Learning
Center  The Learning
Center will be open
starting the second week of classes.  Faculty and student tutors from
Physics
department hold office hours in the Learning Center. It is a
good place to go to work HW (with help immediately available) or to ask
questions of whoever is "on call".
Learning
Center Hours:
Mon. 9 am  noon; Tues., Wed. 9 am  2 pm; Thurs. noon  pm; Fri. 9 am
 noon.
NOTE: Hours may change when Center
opens the second
week of classes.
 Useful Links: The
following are links to three
very helpful
discussions on how to approach studying physics and the necessary
problem
solving that goes with studying physics, written by Dr. Dan Styer,
Physics
Dept., Oberlin College.
 HOMEWORK: The
questions, exercises, and problems on the assignment sheet are to
help you understand the material. You should do the problems
systematically and
carefully in a HW notebook  and ask questions about problems you have
difficulty with. There will also be problem sets handed out which
you should work on carefully  including explanations, diagrams,
etc. These are problem similar to those in the Supplemental Notes
 as well as similar to those used on quizzes and exams.
 Posted Solutions and Hints  Selected problem hints and/or
solutions will be
posted on the bulletin board just outside room E33 in the old Science
Bldg
(Bldg.52).
PHYS 141 NOTES:
[Look
here for comments related to this section of Physics 141.]
This class is scheduled to meet twice a week  Monday and Wednesday
from 68pm  for lecture and
discussion. The format will include
some
lecture and some discussion each day  with occasional problem solving
"workshops". Problems will be worked
on both
individually and in groups. It will be expected that you will attend
class regularly
having read the related material in the text and the supplemental notes
and
that you will have worked on problems (those in the text, the workbook,
the supplemental notes)  so that the work
done in
class is not your first exposure to that material. Any
homework that is actually collected will be problems from the
supplemental notes or from individual problem set worksheets.
You are welcome to come
to my office to discuss the course or physics or
anything else, for that matter, at any of my office hours or whenever
it is
convenient for you. If you can't meet my office hours  and can't find
me just
by dropping by, email me to set up a time to meet.
Expect a diagnostic "pretest" to be sent out prior to the
first class. It is intended to be a way for you to check yourself
to see if you are comfortable with the mathematical ideas that are
assumed to be a part of your background. You may submit the
pretest the first day of class if you want me as your instructor to
evaluate how you did and return it to you the following class
meeting. This exercise will not count toward your grade in any
way  it is just diagnostic on ideas that will be made use of during
the quarter.
<>
The First
Week
<>You should read the Introduction
of my Supplemental Notes and
Problems
booklet to get an idea of what is expected in this course and
what studying physics is about. Then
we will
begin what is the
central theme of this course: Forces  what they are and how they act. By
Wednesday, you should
certainly have read Part I of the Supplemental Notes on Forces and should be starting to
address
some of the problems.
<>
<>By the end of the week, we will begin the formal
discussion of
motion  including developing the equations that describe the motions
of objects in a straight line. This subject, kinematics, will be an
important part of the next few weeks, and you need to have a good
understanding of the equations, where they come from and how to use
them. You should be reading the textbook to help you make the
connections between the motions of objects and how to describe the
motions of objects.
<>
Week
No. 2:
We
will continue with the developement of the kinematics
equations in onedimension and make the connection between the
equations, the description of motion, and the graphical representations
of the motion. The discussion will include freefall problems
(which are the basis for all projectile motion problems, as we will
see). By Wednesday, we will return to the mathematical
description
of vectors, so that the mathematical development of the onedimensional
motion can be extended to two and three dimensions.
There will be a short quiz on the material of the first week.
Week
No. 3:
In
the first couple of chapters, we
have been building the tools needed to deal with Newton's laws.
This week, we will start making the connection between the forces that
act on an object and the resulting changes in motion. On
Wednesday, we will talk about any of the projectile motion problems
that offered difficulty  and will extend the discussion of two
dimensional motion to circular motion problems (something we will come
back to in later chapters). That discussion will lead to Newton's
development of his three laws of motion (and even his law of
gravity). Given the background of how to describe motion in two
dimensions (which, in general, requires making use of vector notation),
and the understanding that forces are always interactions between two
objects, we will be able to show how knowing the forces that act on an
object will lead to a complete description of its motion.
There will be a short quiz on kinematics
during the first part of class. It will just be one or
two problems that are based on the ideas covered so far on the
description of motion in one and two dimensions. The problems
will be similar to those you have already seen in the HW and others in
the Supplemental Notes.
Week No. 4:
Newton's
Laws. The connection
between forces and motion. Be sure and read Ch. 4 and the section
on Forces in the Supplemental Notes and Problems booklet. We will
talk about Newton's three laws  what they mean and how they apply to
problems  and Newton's law of universal gravitation. These
pieces will lead to tying together all the pieces we have been
discussing the first few weeks. We will first concentrate on
force problems that result in onedimensional motion. Then the
discussion will turn to problems in two dimensions which will include
projectile motion problems and problems that involve circular
motion. These dynamics problems are about how the relationship
between forces and accelerations can lead to a complete description of
the motion of objects.
Problems: Ch 4  1, 9, 26, 47; Supplemental Notes and
Problems: Forces  Problems 7, 8, 12, 13, 14, 16
Week No. 5:
We
will continue with the
applications of Newton's laws on Monday  and will answer questions on
the Ch 5 HW problems if you have them. Look in particular at
particular at problems that involve two object which are somehow
connected  ie, either by a string or rope or by physcal contact
through normal force or friction. The idea for problem such
problems for the acceleration due to the forces that act is to first
separate the problem into two problems  drawing the force diagram on each object and writing the
corresponding force equations and then
solving those equations simultaneously.
Chapters 6 and 7 will then expand the discussion to include two and
three dimensional motion  ie, force problems when the motion is not
reduced to only one dimension. We have already done some of what
appears in Ch 6  projectile motion problems. Ch 7 deals with the
description of circular motion problems. We will be in that
material by Wed.
Ch 5 Problems: 6, 10, 17, 19, 27, 34,
35, 40, 51, 55, 57, 70 and Supplement: Newton's Laws  4, 6, 13,
17, 18, 19
EXAM
I
The
exam will cover material up to
through Ch. 5 including Newton's laws and the application of Newton's
laws to problems involving motion in one dimension. The test will
include both conceptual questions and problems to solve. This
will actually be one of a twopart exam. Part B will be the
following week in lab and will include the extension to problems
involving two and three dimensional motion including circular motion
problems, gravitation, and orbit problems.
Week No. 6:
On
Monday, we will deal with the
circular motion  and orbit  problems of the assignment that's due,
the car on a banked turn, and then problems involving objects which are
connected together (for example, blocks tied together by a rope).
All of these problems are just applications of Newton's second law 
and are approached in essentially the same way. The only issue to
always keep in mind in circular motion problems is that the net force
has a component toward the center of the circular path  and the
acceleration in that direction is always v
^{2}/r.
Chapters 7 deals with circular motion. You should also look in
the Supplemental Notes in the section on Kinematics. (That is
just a brief description, but the centripetal acceleration is derived
for uniform circular motion.) Chapter 8 deals with Newton's Third
Law  and how objects interact with each other (something we've been
talking about all along). Look in particular at how to deal with
problems that involve two objects whose motions are related to each
other  for example blocks sliding on other blocks or pushing each
other or tied together by ropes, etc.
Ch 7 Problems: 15, 17, 18, 30, 44 and
Supplement: Kinematics  1316 (circular motion problems);
Newton's Laws: 21, 22, 23
Ch 8 Problems: 22, 30, 46, 44 and Supplement: Newton's Laws  13,
14, 17, 19, 20 (connected objects)
Week No. 7:
Conservation of Momentum.
By
Wed., you should have read Ch. 9 on Impulse and Momentum and be working
on problems involving collisions  like what we did in lab last
week. We will introduce kinetic energy into the discussion as
well, since some kinds of collisions, while conserving momentum, also
conserve kinetic energy and others do not. The idea of the
conservation of momentum follows directly from Newton's Third Law.
Problems: Ch 9  33, 38, 53, 57;
Supplemental Notes: Momentum and Systems of Particles  Problems
7, 8, 12, 13, 14, 16
You should be able to do momentum
conservation problems in both one and two dimensions  including
elastic and inelastic collisions. We will begin the discussion of
energy  which will involve the concepts of work and both potential and
kinetic energy. The important WorkKinetic Energy theorem leads
to the principle of conservation of energy  one of most important
ideas we will encounter. It can become a powerful (and simple)
tool to solve many problems. The energy concepts of kinetic and
potential energy, work, and the workenergy theorem appear in Chapters
10 and 11  and the Supplemental Notes section Work and Energy. I
think it is helpful to look at all of that material together.