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 Gell-Mann, Caltech physicist
Last updated: January 3, 2009
General Physics: Mechanics
An introductory calculus-based 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 hours per week (MTuWTh 2-3). There is
no laboratory for this course.
Instructor: Dr. Ron Brown - Physics
Department
Textbook:
UNIVERSITY
PHYSICS, 12th ed., by Young and Freedman, Addison
Wesley
(2008)
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 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
know that a planet is orbiting a small star 150 light-years 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: UNIVERSITY
PHYSICS, 12th ed., by Young and Freedman
(Addison-Wesley, 2008)
Note: This textbook is new for this
course starting this academic year. You will use the same text 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 80 pages
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 review.
- 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 your
instructor after class or by email to set up a time to meet - or just
stop by
the office.
- Private Tutoring -
Individual arrangements can be
made with Physics
majors available for tutoring in Sci. Bldg. room E-25 (known
affectionately as
"h-bar" - a physics in-joke)
- Drop-In Help - Those
same tutors will also usually help for free
if you just stop by "h-bar" 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 - Sci. Bldg.
52-A03. 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. Solutions will be posted on the web: Problem Solutions
- Posted Solutions and Hints - Selected problem hints and/or
solutions will be
posted on the bulletin board just outside room E-47 in the Science Bldg
(Bldg.52).
PHYS 141 NOTES:
[Look
here for comments related to this section of Physics 141.]
This class is scheduled to meet four times per week 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. Most of
the 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.
The First
Week
Following
an
introduction to the class, expect a diagnostic pre-test on mathematical
ideas
(and maybe even some physics ideas) to be handed out and collected the
second
class meeting - to be done independently. It's purpose is to see where
you are,
what you are bringing in with you, and what of that you are comfortable
with.
It won't "count" toward your grade in any way, it is just diagnostic
- but will lead to a discussion of the tools and ideas that we will
need in
this course.
The
first
meeting will be an
introduction and description of the course, its goals and expectations
and some
discussion of how problems are solved - the general approaches, the use
of
equations, how to make estimates, etc. By Thursday, you should
have read the introductory section of the Supplemental
Notes and Problems and be reading the textbook and starting to
address
some problems.
Then
we will
begin what is the
central theme of this course: Forces and how forces act. By Friday, you
should
have read through the second section of the Supplement on Forces.
In
particular, look at the discussion of the nature of forces as
interactions between objects.
Week
No. 2:
We
will develop the kinematics
equations in one-dimension and make the connection between the
equations, the description of motion, and the graphical representations
of the motion. The discussion will include free-fall problems
(which are the basis for all projectile motion problems, as we will
see). By Friday, we will return to the mathematical description
of vectors, so that the mathematical development of the one-dimensional
motion can be extended to two and three dimensions.
There will be a short quiz on the first week or so of the material.
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 one-dimensional 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 two-part 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.
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 - 13-16 (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
Week No. 8:
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 Work-Kinetic 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 work-energy 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.
UNIVERSITY PHYSICS by Hugh Young and Roger Freedman
Chapter 1 - Units,
Physical Quantities, and Vectors
Ch 1 Problems: 5, 8, 13,
15, 17, 19, 31, 38, 43, 44, 49, 51, 55, 56(a), 59, 89, 94
Chapter 2 - Motion Along a Straight Line
Ch 2
Problems: 7, 10, 13, 19, 25, 40, 52, 64, 69, 79, 91, 98
Chapter
3 - Motion in Two or Three Dimensions
Ch
3 Problems: 3, 7, 13, 19, 28, 34, 37, 41, 47, 58, 75, 81, 91
Chapter 4 -
Newton's Laws of Motion
Ch 4 Problems: 2, 4, 9, 13, 21, 25, 29, 31, 34, 38, 43, 53, 54,
56 and
Supplement: Forces -
7, 9, 10,
12, 13, 14, 16
Chapters 5 - Applying
Newton's Laws
Ch 5
Problems: 2, 4, 10, 17, 18, 24, 28, 41, 45, 54, 62, 72, 80, 86,
96, 114
Supplement: Newton's Laws - 4, 6, 7, 8, 9, 11, 12,
14, 17, 18, 19, 20, 22, 23, 24, 25
Ch 6
Problems: 3, 9, 15, 17, 29, 44, 48, 56, 61, 79, 83, 84, 92
Supplement: Work and Energy - 4, 6, 7, 8, 9, 11, 12,
14, 17, 18, 19, 20, 22, 23, 24, 25
Ch 7
Problems: 3, 5, 19, 25, 29, 32, 38, 39,
42, 46, 49, 55, 66, 78, 79
Supplement: Work and Energy - 11, 12, 14, 17, 18,
19, 20
Ch 8
Problems: 11, 13, 15, 22, 28, 32, 39, 45, 75,
77, 86, 87, 96, 100
Supplement: Momentum - 11, 12, 14, 17, 18, 19, 20
Chapters
9 - Rotation of Rigid Bodies
Ch 9 Problems: 1, 7, 19,
23, 31, 34, 38, 46, 49, 53, 57, 82, 85
and Supplement: Rotational Dynamics - 7, 8,
10, 12, 13, 14, 16
Chapters 10 -
Dynamics of Rotational Motion
Ch 10 Problems: 1, 3, 13,
17, 19, 25, 31, 35, 43, 47, 67
Supplement:
Rotational Dynamics - 7, 9, 10, 12, 14, 16, 17, 18, 22, 24
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