The introductory course in college physics1 has been criticized as fragmented and lacking in a theme or “story” to tie together the disparate chapters.2 As physicists, we see it as highly organized and hierarchical, developing from the great principles of Newton, Maxwell, etc. But to the student, it's just the chapter on lost hikers, the chapter on cars crashing and sticking together, etc. The purpose of this paper is to consider a certain subset of introductory course subjects, one that seems, if anything, more fragmented than the rest, and then to suggest a way of presenting these subjects that constitutes a story.
REFERENCES
1.
I am thinking primarily of the algebra-based course and also of a rigorous high school course in physics.
2.
Sheila Tobias, Revitalizing Undergraduate Science (Research Corp., 1992).
3.
Keeping the burner in place while heating a beaker of water allows one to argue that the time of heating is proportional to the heat entering the water. Thus heat needed is found to be proportional to the temperature change and to the mass of water. Complications such as heat going into the beaker and heat escaping to the air seem not to have significant effects on the results. To heat another substance, try glycerine, which has a specific heat (0.6) significantly different from unity.
4.
By comparing the time to raise the temperature of water a given amount to the time to boil a certain weight (around 50 g) of water, one gets a reasonable value (within 10%) of the latent heat.
5.
For present purposes it is convenient to let W stand for the work done by the environment on the system, although many texts use the opposite convention.
6.
Thus, one type of first law calculation might be: Suppose a force of 10 N moves a mass of 1 kg through 3 m, as the mass goes from rest up to 6 m/s. Then W = 30 J, (kinetic energy = ½mv2), and so “Friction” is not invoked.
7.
See A.B. Arons, A Guide to Introductory Physics Teaching (Wiley, New York, 1990), Chap. 5.
Other references:
C. M.
Penchina
, “Pseudowork-energy principle
,” Am. J. Phys.
46
, 295
–296
(March 1978
);B. A.
Sherwood
, “Pseudowork and real work
,” Am. J. Phys.
51
, 597
–602
(July 1983
);A. B.
Arons
, “Development of energy concepts in introductory physics courses
,” Am. J. Phys.
67
, 1063
–1067
(Dec. 1999
);R. C.
Hilborn
, “Let's ban work from physics!
” Phys. Teach.
38
, 447
(Oct. 2000
);Dick C. H.
Poon
, “Work, energy transfer, and sliding friction
,” Phys. Teach.
44
, 232
–234
(April 2006
).8.
The subject is further weakened by the fact that noncalculus students are not easily convinced that work is the area in the P-V plane and in any case cannot find areas for realistic cases.
9.
Some textbooks offer a brief discussion of the statistical interpretation of entropy by using models with a few molecules and making the case that the less ordered macrostates are more probable. The value of these treatments seems uncertain. See, for example: Douglas C. Giancoli, Physics, 2nd ed. (Prentice Hall, Englewood Cliffs, 1990), Chap. 12; Raymond A. Serway, Jerry S. Faughn, Chris Vuille, and Charles A. Bennett, College Physics, 7th ed. (Thomson Brooks/Cole, Belmont, CA, 2006), Chap. 12.
10.
See Appendix 1 online at the FTP site E-PHTEAH-45-015708.
http://ftp.aip.org/cgi-bin/epaps?ID=E-PHTEAH-45-015708.
11.
One line of evidence is based on electroplating of ions from solution, together with measurement of the charge on the electron. Another involves the diffusion of gases.
12.
See Appendix 2 online at the FTP site E-PHTEAH-45-015708.
http://ftp.aip.org/cgi-bin/epaps?ID=E-PHTEAH-45-015708. For more information on EPAPS, see http://www.aip.org/pubservs/epaps.html.
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© 2007 American Association of Physics Teachers.
2007
American Association of Physics Teachers
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