Physics 326:Computer Based Experimentation and Physics Computing

1
Physics 326 Computer Based Experimentation and
Physics Computing
Instructor Prof. Weida Wu
Office Serin W 117
Phone [phone] ext. 8299
e-mail wdwu_at_physics.rutgers.edu
Office Hour Wed. 3-4 PM
Lab Assistants Theodore Siu (tsiu_at_physics.rutger
s.edu) Textbook An Introduction to Error
Analysis, J.R. Taylor, 2nd Ed. University
Science Books. Web Site for Course http//www.ph
ysics.rutgers.edu/ugrad/326/
2
Lecture and Lab sessions
Lecture (Wu) Wednesday (810-930PM) SEC 209
Lab Sect. 3 (Siu) Monday (640pm-930pm) Serin 101
Lab Sect. 1 (Wu) Tuesday (1020am-120pm) Serin 101
Lab Sect. 2 (Siu) Tuesday (320pm-620pm ) Serin 101
Lab Sect. 4 (Siu) Thursday (640pm-930pm) Serin 101
No more than 2 people per group.
3
Preparation for the labs
Lab instructions are posted to the course web
site. Each lab will be discussed in the
Wednesday lectures before the lab. You are
expected to download, print, and read these
instructions before coming to lecture. In
addition, you should understand what to do in the
lab BEFORE coming to a lab.
4
Reports and quizzes
Lab Reports Lab reports are to be prepared
individually and handed in during the lab session
of the following week, i.e., you have one week to
write your report. No late reports will be
accepted. Copied lab reports will not be
accepted. Do not write a report if you have not
actually done the lab it will not be accepted.
Type and print your reports. No hand written
report will be accepted. Quizzes (6-8) Short
quizzes will be given occasionally during
lectures through the semester. Topics in the
quizzes are lecture and lab contents, reading
assignments, and homework. Make-up quizzes will
not be offered unless you have a documented
medical reason for missing the quiz.
5
Grading
The course grade will be based mostly on the lab
reports (85), with the remainder determined by
lab preparation and participation, quiz scores,
and lecture attendance.
Grade cutoffs  (Tentative)
A B B C C D F
90 85 75 70 65 50 lt50
6
Lab report format

• Introduction (a short overview/background)
• What is this about?
• Why is it interesting?
• Method
• techniques, instruments, procedure, data
  analysis, error analysis
• Do NOT copy from lab manual
• Results and discussion
• tables and figures
• connect the results back to the theory (intro)
• Conclusion
• one or two sentences
• References (if any)

7
Course schedule
Week Lectures (Wednesdays) Section 1, 2, 3 (Monday, Tuesday) Section 4 (Thursday) Section 4 (Thursday)
Sept. 2 Sept. 6 1, Sept. 4 No labs/only lecture Lab 1 Lab 1
Sept. 9 13 2, Sept. 11 1 - Propagation of Error Lab 2 Lab 2
Sept. 16 20 3a, Sept. 18 2 - Wavelength of Light Lab 3a Lab 3a
Sept. 23 27 3b, Sept. 25 3a - Distribution Functions Lab 3b Lab 3b
Sept. 30 Oct. 4 4, Oct. 2 3b - Distribution Functions Lab 4 Lab 4
Oct. 7 11 5, Oct. 10 4 - Least Squares Fit Lab 5 Lab 5
Oct. 14 18 6, Oct. 17 5 - Damped Harmonic Motion Lab 6a Lab 6a
Oct. 21 25 7a, Oct. 24 6a - Forced Harmonic Motion Lab 6b Lab 6b
Oct. 28 Nov. 1 No lecture 6b - Forced Harmonic Motion Lab 7a Lab 7a
Nov. 4 8 7b, Nov. 7 7a - Fourier Analysis Lab 7b Lab 7b
Nov. 11 15 8, Nov. 13 7b - Fourier Analysis (contd) Lab 8a Lab 8a
Nov. 18 22 No lecture 8a - Onset of Chaos Lab 8b Lab 8b
Nov. 25 29 Thanksgiving No lecture, No labs Thanksgiving No lecture, No labs Thanksgiving No lecture, No labs Thanksgiving No lecture, No labs
Dec. 2 6 No lecture 8b - Onset of Chaos (contd) 8b - Onset of Chaos (contd)
Dec. 9 13 All lab reports due makeup labs no class meetings All lab reports due makeup labs no class meetings All lab reports due makeup labs no class meetings All lab reports due makeup labs no class meetings
10 lectures, 12 labs, 8 reports, 6-8 quizzes
8
Lab 1 Propagation of error
Errors, or uncertainties, are inevitable in
measurements. Note that here errors mean random
errors. One should always avoid systematic
errors.
9
How to report errors?
Measurement and error

• Rules of reporting error
• (measured value of x) xbest dx
• Experimental uncertainties should almost always
  be rounded to one significant figure.
• The last significant figure in any stated answer
  should usually be of the same order of magnitude
  (in the same decimal position) as the uncertainty.

10
An example

• Rules of reporting error
• (measured value of x) xbest dx
• Experimental uncertainties should almost always
  be rounded to one significant figure.
• The last significant figure in any stated answer
  should usually be of the same order of magnitude
  (in the same decimal position) as the uncertainty.

11
One exception of rule 2
If the leading digit in the uncertainty dx is a
1, then keeping two significant figures in dx is
a better way.
12
Exercises how to report errors
 
 
 
 
 
13
The propagation of errors
If q is a function of one independent variable x,
Then
For example
14
A quick estimation of error propagation
Provisional rules (for quick estimation)
Examples
More precisely
15
Propagation of independent errors
If the uncertainties ?x, ?y are independent of
each other,
This can be generalized to multivariable
functions
16
Statistical Analysis of random error
Random error is treated as a random variable that
follow a random distribution.
How to evaluate random errors?
A Repeated measurements.
17
The mean and the standard deviation
18
The standard deviation of the mean
More discussion of this topic in lab 3.
19
Lab 1 Torsion Pendulum
Moment of inertia
Torque constant
20
Torsion Pendulum
Modulus of rigidity (a.k.a. modulus of torsion,
the shear modulus of elasticity)
21
Quantities to measure
L length of the steel wire d diameter of the
steel wire m mass of the rectangular block a
width of the rectangular block b length of the
rectangular block T period of torsional
oscillation