Wednesday 11 January 2012
Class meeting
Topics
Textbook sections
Ponderables
Mini-labs (deliv.)
Lab
Demonstrations
Mini-lectures
Quiz
Other
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PHYS 116 SCALE-UP
2
Measurement
Chap. 1
Moon Pie
Common Cents (spreadsheet)
FCI
Questions or concerns about class procedure, including Mastering Physics (first HW assignment
due Monday)
FCI (35 minutes): diagnostic, not part of grade, helps evaluate teaching
Mini-lab: Common Cents (45 minutes): First example of a mini-lab. Explain deliverable.
o Equipment: 3-5 digital balances, ~200 pennies, at least one Vernier caliper for each
group (more is better)
Ponderable: Moon Pie (20 minutes)
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Wednesday 11 January 2012
PHYS 116 SCALE-UP
COMMON “CENTS”
In this exercise, you will investigate physical properties of the U.S. Lincoln one-cent coin,
commonly known as a penny. By doing so, you will apply basic scientific reasoning skills and
gain experience making measurements with common laboratory instruments and properly
reporting results.
Pre-lab (to be turned in at the beginning of next class):
A few years ago a sample of pennies was collected from general circulation. A histogram
showing the number of pennies from each year is provided below.
70
60
50
40
30
20
10
2002
2000
1998
1996
1994
1992
1990
1988
1986
1984
1982
1980
1978
1976
1974
1972
1970
1968
1966
1964
1962
1960
0
Answer the following questions in a few sentences each:
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What inferences can you make from this sample?
Why does this histogram not follow the normal (Gaussian or bell-shaped) distribution
curve?
What year do you think the sample was obtained?
Is there anything you find surprising about this sample?
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Wednesday 11 January 2012
PHYS 116 SCALE-UP
Explorations
You will be shown the basics of using a vernier caliper (written instructions are available on the
Sakai site in the document “Measuring Instruments” in the “Course Information” section of the
site); you will also be instructed briefly on using the digital scale. Finally, you will be introduced
to the idea of uncertainty and how you might propagate it by the upper/lower bound method
when calculating an answer based on several uncertainties. All responses are to go in your lab
notebook.
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Determining density: Determine a basic formula for density and calculate the density
of a penny. Use vernier calipers and a digital balance to find the density of a typical
penny as precisely and accurately as possible. Carefully consider the procedure you will
use to accomplish this task. Report your intermediate and final results in your lab
notebook, using the descriptions below as a guide. Be sure to propagate your
uncertainties in the individual measurements to the final value of the density.
Mass = _______ ± ______ g
Diameter = ________ ± ______ cm
Volume = ______________ ± ______________
Thickness = _______ ± ______ cm
Density = _______________ ± ______________
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Comparing values: Do your results agree with the findings of other groups? In thinking
about why or why not, examine the physical properties of several pennies and think
about how they are similar and different. Make brief notes about your observations. Of
the three direct measurements you made for calculating the density, which was least
precise and why? Record your findings in your lab notebook.
Deliverable: Create an Excel-compatible spreadsheet and enter your measurements (and
uncertainties) for mass, diameter, and thickness. Use the spreadsheet to calculate the density
and its uncertainty using both the upper/lower bound approach and the propagation of
uncertainty in quadrature (put the uncertainty values calculated by these two different
methods into different columns of your spreadsheet). Format your results to an appropriate
number of significant figures. Refer to the document “Measurement and Error Analysis” posted
on the class Sakai site (in the “Course Information” section) for more information about the
upper/lower bound method and propagation of uncertainty in quadrature (see pgs. 12-16).
Submit your spreadsheet via the Sakai site before the next class meeting.
Remember, “It is better to be roughly right than precisely wrong.” ( Alan Greenspan)
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Wednesday 11 January 2012
PHYS 116 SCALE-UP
MOON PIE
A cup (U.S. measure) of cream cheese has a mass of 8.18 ounces. If the Moon were made of cream
cheese, what would be its diameter (assuming it had the same mass as the real Moon)? What does that
tell you about what the Moon is made of?
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