Physics I Laboratory Grading Rubric
for Written Reports (5 required beyond Lab #1). Each
experiment will be tallied for a total of 100
points. Fall 2011
DESCRIPTION OF THE EXPERIMENT. 30
points.
Clearly identifies the purpose of the
experiment. This should be written in
clear, succinct prose. Use first
person or third person, but should be consistent
- what is being tested?
- what results are predicted?
- discusses the tools and equipment
- uses clear diagrams
- sets the tone of writing for one's
peers
EXPERIMENTAL RESULTS. 40
points.
- Results are presented in clear,
well-labeled graphs. Most
experiments use computer-generated graphs.
The computer generated graphs should have appropriate
scales on the axes, points plotted as a scatter plot with no
connecting lines (unless appropriate to show continuity), a
trend line shown when appropriate. All graphs and drawings should
be labeled with Figure #. Followed by the caption in one or
two sentences. The figure label and caption should be at
the base of each figure. Example: Figure 1. A plot of the
velocity vs. time for a fan cart with the thrust directed
in-line with the track.
- Appropriate use of the trend line. Sometimes the trend line is
inappropriate and has no relevance to the experiment and should
not be included.
- Appropriate use of simple tables. Raw computer data should not be
presented in extensive tables. When
tables are used, the tables should be small and concise and
serve to provide a short summary of the data. All tables should be labeled
with a Table # followed by a caption of one or two
sentences. The numbering of tables is Roman
numerals. Example: Table I. Data results for the different thrust
angles and slope measuring techniques. The percent
differences between the techniques is also shown in the
respective columns.
- Calculations should be demonstrated
with a sample calculation. The
calculations may be hand-written, but it is possible with a
little more effort to show the formulas and calculations with an
equations editor on the word processor. Be sure
to use an equation editor, don't try to use standard typing
for equations.
- Units and dimensions should be
shown and correctly derived.
- Proper use of significant digits
should be shown, but round-off errors should be prevented - see
below.
DISCUSSION OF THE RESULTS (this is
often the most difficult part of the report).
30 points.
- The significance of the results is
clearly presented. It basically
answers the purpose of the experiment or why the experiment was
done
- The results are compared with the
predictions made before the lab
- Numerical results are presented in
a simple table along with percent differences fom published
results. A comment should be included on the quality of
the results based mostly on the percent differences
- The student clearly explains what
she or he has learned by doing the experiment and that the
student understands the principles presented in the
graphs. What is the "bottom line" of the experiment?
- The report is basically free from
grammar errors, spelling errors (use of a spell-checker and peer
proofreading is encouraged). Sentences
and paragraphs are succinct and free from run-on errors.
- The report
communicates the physics and the student clearly shows an
understanding of the physics in the whole report.
SUGGESTIONS FOR STYLE.
The style elements are not as "ironclad" in the grading rubric,
but attention to the style suggested here should help make more
meaningful and readable reports and should help students better
communicate in their chosen professions.
A. Organization when
several smaller experiments are involved.
Many physics laboratories involve
more than one experiment that are related. As an
example, the first laboratory involves measuring the speed of a
ball that is tossed between two people as well as the motion of a
bowling ball as it rolls along a hallway. It is much better
to complete the write-up (description, results, discussion) for
the first part of the lab before beginning to discuss the 2nd part
of the lab. It makes reading (as well as writing) the
reports easier if the report is organized to present the complete
report of the first experiment (description, results, and
discussion) before introducing the second experiment.
Beginning students are often tempted to describe the first
experiment followed by a description of the second experiment
before any results are presented. This breaks the reader's
train of thought - especially when the introduction is so well
done prompting the reader to be anxious to see the results - only
to have the thought process interrupted by a different
experiment. Thus, when
appropriate, reports should be organized to complete the results
and discussion of the first experiment before introdcing the
second experiment. A final discussion tying all
experiments together is also appropriate with multiple
experiments.
B. Avoid round-off errors in
intermediate calculations.
The best way to show this is an example.
Suppose a student measures the sides of a right triangle to be
4.58 cm and 3.28 cm. See the diagram. Note that both
of these measurements have 3 significant digits. A student
does the calculation correctly on a calculator and presents the
result as
5.633364891430 cm.
Here the student will have points docked for significant digit
violations. This 13 digit result should be rounded to no
more than three significant digits
(5.63 cm) to avoid the egregious significant
digits error and earn credit for the correct result.
Having been so severely reprimanded of the significant digits
mistake, the student typically tries another tactic to avoid
excess digits. In calculating the squares in the Pathegorean
formula, the student rounds (4.58 cm)
2 =
(20.97640000000 cm
2 = 21.0 cm
2).
(3.28 cm)
2 = (10.75840000000 cm
2
= 10.8 cm
2)
. The student then takes
the square root of the sum of the "rounded squares" to be 5.64 cm:
Notice that the student obtained a small error (5.64 cm)
rather than 5.63 cm. This error seems small and
insignificant, but represents a subtle error due to
rounding-off intermediate calculation results. When
calculations are more complicated than this simple example,
several round-off errors may accumulate and become
significant. The best method is to use and keep the full
internal precision of the calculator for intermediate
calculations, save rounding until the end. If
intermediate results need to be written down and re-entered,
they should contain one more significant digit than needed for
the result. Also, don't forget the rules for
rounding: 5.635 to 5.639 all round to 5.64.
C. Use computer tools for
equations and line drawings.
Although it is not required that the students use the tools of
computer word processors to produce equations and line drawings
(it is satisfactory that these be done by hand) the gain in
readability and appearance is remarkable. It takes a little
longer to use these tools, but once they are completed, there is
much less tendency to forget to hand-draw the equations and
diagrams when turning in the report. Be sure to install the
Equation Editor if you are using MS Office. If you do not
have MS Word for your own computer you may purchase MS
Office 2007 for about $86.00 including postage from
www.scholarbuys.com. An even lower cost alternative is to
use Open Office (free from Openoffice.org 150 MB download).
Open Office works on any platform. If a student includes
electronic equations and line drawings with the final report,
significant paper may be saved by submitting the lab report
electronically as an e-mail attachment.