Welcome to
Principles of Physics I
(PHYS 2010)
Professor Blaine Norum
Note on enrollment: If you are waitlisted and not currently registered in a
discussion section: Come see me. In most cases I can sign you in. . Note: you
MUST attend the first meeting of your discussion section. Failure to do so may
result in your being dropped from the roster and replaced by someone waiting
UVaCollab site:
-Syllabus
-Resources (lecture slides, practice exams, etc.)
-Gradebook
-Feedback
MasteringPhysics: web interface for assigned problem sets
Lecture rules
No cell phones.
No laptops EXCEPT in very last row.
Do not interfere with the learning environment
Make space for your fellow students
If you are sick... don’t come to class.
2
Lectures
Format
• Electronic
• Slides
slides
will be available after lectures (rarely before)
demos to build intuition, relate to the real
world, and encourage engagement
• Frequent
NOTE: I may occasionally miss a class. In this case,
your instructor will be another professor with
experience in this class.
i>Clickers
• Questions
in lecture will challenge your conceptual
understanding, encourage your engagement and provide
me with feedback
•1
point for participation,
•A
second point for correct answer (if scored)
• 2%
of your course grade
• You
MUST register your i>Clicker for THIS class: go to
UVaCollab site.
3
Mastering Physics
A web-based homework system
• Instantaneous
• Multiple
• Hints,
attempts at problem solving (guessing discouraged)
tutorials, and other support
• Excellent
• Well
feedback
feedback to instructors
designed interface
• MCAT
study guides (mostly practice MCAT quizzes)
Register using your access code at MasteringPhysics.com
•sign up for Walker 4th edition
•Use this class code:
-Section 1: MPNORUM25409
-Section 2: MPNORUM95999
•use your email/computing ID
•Problems: use the online help (“Ask a question”).
There is an introductory assignment (not graded) and also
your first assignment (due Friday) available now
4
5
Exams and Grading
Midterm Exams:
Three midterm tests will be given at the dates and times shown in the syllabus. The tests will be
administered during regular class time. The tests will consist of multiple choice questions.
TEST DATES IN SYLLABUS ARE NOT WRITTEN IN STONE! THEY MAY SHIFT SLIGHTLY!
Final Exam:
Final Exam
45%
Three Midterm Exams
45%
Problem Sets
8%
Quizzes in Lectures (iClickers) 2%
Are they hard?
Raw averages on the 3 midterms last year: 73%, 77%, 60%
On the final: 68%
Is there a curve?
yes. With curve, class average is usually B-/B
6
Learning in PHYS 2010
Study Techniques
•
Read the book
- Keep a pencil in hand, along with scratch paper (& calculator)
-
•
Work example problems.
Work end-of-chapter problems
-
start with at least one “one dot” problem; a warm-up drill
-
most odd-numbered questions have answers in the back of the book.
-
focus on completing the problem, correctly. Small mistake = zero
points on the exams
•
Take advantage of web resources (example: classic problems may
crop up on study sites)
• Take advantage of office hours
My Office Hours
Tuesday 3-4:30, Thursday 3-4:30, or by appointment. Physics
Bldg. Rm 136.
TA Office Hours
Posted on Collab site.
You can attend office hours for ANY TA from this course
7
Feedback
email
Feel free to send comments to me directly.
MasteringPhysics comments
These are sent directly to me, and also logged for the
MasteringPhysics developers
Anonymous feedback
...via UVaCollab site. I have often received useful constructive criticism
in this format.
But remember, since it is anonymous I cannot respond to you
individually unless you E-mail me directly
8
Check Syllabus for reading assignment:
(next lecture completes Chapters 2 and 3!)
Do your reading. Have a pencil in your hand.
Do examples. Practice drawing figures.
Register at MasteringPhysics.
look at the introductory assignment (not for credit)
work Assignment #1 (for credit, due Tuesday, Sept. 2 at 11:59pm)
Register your iClicker
• Go to Collab site, Registration and Course Materials, follow directions
• bring it to every lecture for extra credit quizzes and questions
when we finish, Please exit out the back doors So the next class can come in the front.
9
10
Lecture 1
Introduction to Physics
11
A Quantitative Science
Physics: the study of the fundamental laws of nature
• these laws can be expressed as mathematical equations
• much complexity can arise from relatively simple laws
• this complexity can be analyzed in terms of these simple laws
Physics is a quantitative science, based
on careful measurements.
If you can’t measure it, it ain’t physics!
12
Science is NOT just a collection of formulae!
Science is a way of understanding the
universe – mathematics is the language of
science:
• Concepts (mass, velocity, momentum, etc.)
are the vocabulary
• Equations are the grammar
Together, they enable us to describe the wrold
around us
13
Units of Length, Mass, and Time
SI units of length (L), mass (M), time (T)
Time: the second
One second is the time for radiation from a cesium-133 atom to complete
9,192,631,770 oscillation cycles.
Length: the meter
Was: one ten-millionth of the distance from the North Pole to the equator
Now: the distance traveled by light in a vacuum in 1/299,792,458 of a second
Mass: the kilogram
One kilogram is the mass of a particular platinum-iridium cylinder kept at the
International Bureau of Weights and Standards, Sèvres, France.
14
Units of Length
15
Units of Mass
16
Thinking quantitatively allows us to
describe objects that are outside our
common experience...
... and sometimes find connections we
wouldn’t have seen.
1041 kg
1021 m
10-10 m
10-25 kg
10-14 m
10-27 kg
10-15 m
Dimensions and Units
• Any valid physical formula must be dimensionally
consistent – each term must have the same dimensions
From the table:
Distance = velocity × time
Velocity = acceleration × time
Energy = mass × (velocity)2
18
The density of iron is about 8000 kg / m3 . You have an iron brick with
dimensions 20 cm x 10 cm x 10 cm. What is the mass of the brick ?
Density = [M] / [L3]
Volume= [L3] = 0.2 x 0.1 x 0.1 m3 = 2 x 10-3 m3
Mass = [L3] x [M] / [L3] = (8 x 103 kg / m3) (2 x 10-3 m3)
= 16 kg
19
Density of big nuclei
density = [Mass]/[Volume] = [M] / [L3]
Neutron Star:
Neutron Star
• 104 m
• 2.7x1030 kg
Lead Nucleus:
Nucleus of Lead-208
• 5x10-15 m
• 2.5x10-25 kg
20
Converting Units
Converting feet to meters:
0.3048 m = 1 ft
(this is a conversion factor)
Or: 1 = 0.3048 m / 1 ft
316 ft × (0.3048 m / 1.0 ft) = 96.3 m
Note that the units cancel properly – this is the key to using the
conversion factor correctly!
There are 1.6 km to 1 mile.
If something is traveling with a speed of 15 m/s, what is the speed in miles per hour?

1

1

1
21
Significant Figures
• accuracy of measurements is limited
• significant figures: the number of digits in a quantity
that are known with certainty
• number of significant figures after multiplication or
division is the number of significant figures in the
least-known quantity
22
Significant Figures Example
A tortoise travels at 2.51 cm/s for 12.23 s. How far does the tortoise go?
(from a calculator: 2.51 x 12.23 =30.6973 cm)
Answer: 2.51 cm/s × 12.23 s = 30.7 cm (three significant figures)
23
Scientific Notation and Significant Figures
• Leading or trailing zeroes can make it hard to determine number
of significant figures: 2500, 0.000036
(Each of these has two significant figures)
In this case, the trailing zeros are necessary. They are only clearly
significant if they are “necessary”, as in 2500.0
• Scientific notation writes these as a number between 1 and 10,
multiplied by a power of 10:
2500 = 2.5 × 103
0.000036 = 3.6 x 10-5
We can indicate three significant figures as 2.50x103
(now the trailing zeros mean something!)
24
Order-of-Magnitude Calculations
Why are estimates useful?
•
•
as a check for a detailed calculation – if your answer is very
different from your estimate, you’ve probably made an error
to estimate numbers where a precise calculation cannot be done
Choose useful units, and ignoring the details you don’t need
Example: How many times will your heart beat during your life?
70 times per minute? call it 100.
60 minutes / hour? call it 50
24 hours/day? call it 20
365 days/year? call it 400
80 years? 130 years? call it 100.
1x102
5x103
1x105
4x107
4x109
4 billion times... if you live to a ripe old age
25
Scalars and Vectors
Scalar – a numerical value. May be positive or negative.
Examples: temperature, speed, height
Vector – a quantity with both magnitude and direction.
Examples: displacement (e.g., 10 feet north), force, magnetic field
“position” is obviously a vector.
Example: when looking at a 2-dimensional map “2 miles South”
Note: this implicitly has 2 numbers in it: “0 miles East”
“position” corresponds to “displacement”, a vector.
length of travel is “distance”, a scaler
26
Position, Distance, and Displacement
Before describing motion, you must set up a coordinate
system – define an origin and a positive direction.
The distance is the total length of
travel; if you drive from your house to
the grocery store and back, you have
covered a distance of 8.6 mi. Your net
displacement is zero.
27
Position, Distance, and Displacement
If you drive from your house to the
grocery store and then to your friend’s
house, your displacement is -2.1 mi and
the distance you have traveled is 10.7 mi.
28
Average Speed
The average speed is defined as the distance
traveled divided by the time the trip took:
Average speed = distance / elapsed time
If you drive from your house to the
grocery store and then to your
friend’s house, your displacement is
-2.1 mi and the distance you have
traveled is 10.7 mi. The trip takes 30
minutes (with traffic and lights).
What is your average speed?
10.7 miles
sav =
0.5 hours
= 21.4 miles/hr
29
Average Velocity
Average velocity = displacement / elapsed time
If you return to your starting point, your average
velocity is zero.
30
Check Syllabus for reading assignment:
(next lecture completes Chapters 2 and 3!)
Do your reading.
Register at MasteringPhysics.
work Assignment #1 (for credit, due Tuesday, Sept. 2 at 11:59pm)
Register your iClicker
• Go to Collab site, got to Registration and Course Materials and follow instructions
• Bring it to every lecture for extra credit quizzes and questions
Please exit out the back doors - So the next class can come in the front.
31