Physics 103
Lecture 0
Daniel R. Marlow
Physics Department
Princeton University
Physics 103 Web Page:
http://www.hep.princeton.edu/~marlow/p103/
September 15, 2000
Announcements
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Class/Instructor Assignments
! these will be posted over weekend
! check for your assignment
! if you need to change times, go to
whichever time you want, but be sure to
see Mr. Kicinski to register the change.
! show up in McDonnell at the time you
signed up for either 9:00 or 10:00AM
September 15, 2000
Course Staffing
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September 15, 2000
Course Director: Prof. Daniel Marlow
! 381 Jadwin, x8-4383
! marlow@princeton.edu
Lab Manager: Prof. Eric Prebys
! Working hard to make Physics 103
lab fun and profitable.
Course Manager: Mr. Martin Kicinski
! First stop for administrative matters.
! 208 Jadwin, x8-4408
Books and Materials
• Required text:
•
September 15, 2000
! Tipler (4e), extended.
! Available at U-store.
Learning Guide & Lab Manual
! Available on WWW
! Available in printed form from Ustore (this will probably be more
convenient).
. . . Books and Materials
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September 15, 2000
Lab notebook
! WW15 5 x 5 Quadrille “green tint”
! Available at U-store.
Calculator
! Basic scientific calculator with trig.
Functions is strongly recommended
! Advanced features (graphing,
extended memory, etc.) can not be
used during exams and quizzes.
Course Organization
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September 15, 2000
Lectures
! Tuesday at 9:00 AM or 10:00 AM
! Concepts
! Demonstrations
! This is what you’ll remember 30 years
from now.
! You can attend either the 9:00 or the
10:00 lecture. They are identical.
. . . Course Organization
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September 15, 2000
Classes
! Core of the course
! Instructor plus ~22 students
! M-W-F at 9:00 or 10:00 AM
! Quiz during last 20 minutes of
Friday’s class
! You can not change sections without
approval (see Mr. Kicinski).
. . . Course Organization
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September 15, 2000
Labs
! One 3-hour lab most weeks
(exceptions during midterms and
Thanksgiving)
! Demonstrate the concepts for yourself
! Learn laboratory technique
! Introduction to error analysis.
Physics 107 Option
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September 15, 2000
Covers same material as Physics
103/104 sequence in three semesters
instead of two.
Designed for students who have not had
strong high school preparation in math.
Meets at 10:00 AM only.
If you are interested contact me by the
end of today (8-4383 or
marlow@princeton.edu).
Physics 103/105 Lab
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Labs start next week
Go to the section you signed up for
! 201 or 202 McDonnell
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September 15, 2000
Lab manual: read intro handouts, which
describe digital camera and software,
and Experiment #0
You cannot miss lab.
If you must miss your regular
lab section, contact your AI at least one week in advance to
arrange to go to another section. Missing one lab lowers your
course grade by one full letter. Two misses and you fail the
course.
Lab work counts 15% toward your final
grade in 103.
Structure of the Lab
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Before lab —
! read manual
! do pre-lab problem set
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In lab —
! assemble in adjacent classroom
! your AI will give you instructions
! do lab — maintain your notebook
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Leave notebook in the lab
!
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!
!
September 15, 2000
your notebook will be graded
you do the lab in 3 hours
no formal lab reports
DO NOT TAKE NOTEBOOK FROM LAB
Error analysis in lab
• You will be introduced to error
analysis but it shouldn’t cause you
too much pain and suffering.
September 15, 2000
Homework
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September 15, 2000
Extremely important to work problems.
Best way to test your knowledge of the
material.
Build all-important problem solving skills
through practice.
Falling behind is generally fatal.
Quizzes and exams will draw from
homework.
. . . Homework
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Learning Guides
! Developed by Princeton faculty over
many years.
! Many of the problems are real gems.
! Designed for self-study.
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September 15, 2000
Book problems
! List will be posted each week
! Solutions will posted on WWW.
Quizzes
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September 15, 2000
One each week
Designed to encourage you to do the
homework and to keep up with the
material.
Exams
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General
! Closed book, no notes.
! Hard-to-remember details such as the
numerical value of physical constants will
be given.
! Each problem is graded by the same
person to ensure uniformity and fairness.
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September 15, 2000
Exams
! 1.5 hour midterm on ~Oct 25.
! 3 hour final during exam period
. . . Exams
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September 15, 2000
All problems will be based on concepts
illustrated in the homework.
Some problems will be very thinly
disguised homework problems (for
example only the numbers will be
changed).
Grading
Lab
15%
Final
40%
Midterm
20%
Quizzes
25%
September 15, 2000
A Typical Week in Phys 103
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Do reading over weekend.
Monday Class
! Review of Concepts
! Illustrative Examples
! Will move too quickly to follow unless the
reading has been done ahead of time
! Come armed with questions
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September 15, 2000
Tuesday Lecture
! Demonstrations
! Conceptual Discussions
. . . A Typical Week in PHY103
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Wednesday class
! Working problems
! Will be far more useful if you have
attempted the problems ahead of time
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September 15, 2000
Friday Class
! More problem solving
! Last chance to ask questions
! Quiz
Some comments
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This is not a “weed out” course.
We want you to succeed.
We want you to leave with a firm
grounding in physics.
We have a lot of material to cover in a
short time.
! Ideally we would have three semesters
for the course instead of two, but there
are other courses you must take.
! Pace will be fast
September 15, 2000
. . .Some comments
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Available resources
! Thursday night review sessions
! Other campus organizations (see the
course WWW page for details).
! Your class instructor’s office hours.
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In the end, it will be up to you.
! Must struggle on your own.
! Time spent in active mode (solving
problems or arguing with others about
how to do so) will be far more productive
than time spent listening to experts.
September 15, 2000
We want your input
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Ways to give it
! E-mail: marlow@princeton.edu
! Phone: 8-4383
! In person. Drop by my office (Jadwin
381) or send e-mail for an appointment.
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Do we listen?
! Yes.
! In a course of 300 students, we can’t
follow every suggestion.
! We do follow as many as we can.
Student comments make a difference.
September 15, 2000
Experimental “Errors”
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Poor choice of words.
! Doesn’t mean that someone goofed up.
! Experimental uncertainty a much better
choice.
! Experimental results are almost
meaningless unless an error is quoted.
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Example:
x = (1000 ± 10) mm
central value
September 15, 2000
error
A Classic Example: Radioactive Decay
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September 15, 2000
How many decays happen in a given
time?
22
Five gr. natural Uranium ≈ 10 atoms. .
Half life is ~5 billion years
We expect about 50,000 decays per
second, but only a small fraction register
in the Geiger counter.
Apparatus
U source
Amplifier
0000000107
Scaler
Geiger
Counter
1.0 sec
Each one-second measurement can be thought of as a
separate experiment.
September 15, 2000
Timer
Questions
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September 15, 2000
How do we estimate the error?
How do we combine the separate
experiments to get one good
measurement?
What will the error on that measurement
be?
Answers
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How do we estimate the error on each
measurement?
! Observe (or compute) standard deviation
of tennis-ball histogram.
! Statistically this should give σ 1 = Ν = 100 = 10
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How do we combine the experiments to
get one good measurement?
! Average the results.
What will the combined error be for M
measurements?
σ
σ many =
September 15, 2000
1
M
Check
The fractional error in a single measurement is
σ
f1 = 1
Ν
= N
N
= 1
N
According to previous slide, the error on the
average is
σ
fM = Μ
Ν
(
σ
=
1
Μ
)
Ν
= 1
MN
Which makes sense since the total number of
counts is M × N
September 15, 2000