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"Re: operational F, m, and a"



In his Phys-L post of 16 Oct 2001 14:15:26-0400 titled "Re:
operational F, m, and a" John Denker wrote:

DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD
"Consider a rather more direct operational definition. . .(of force).
. . : Take a spring scale, like they sell at the fishing store. When
the spring is extended a certain amount, it indicates a certain
force. Two fish scales give a resultant force according to a vector
sum law. Blah blah et cetera et cetera.

. . . (For an operational definition of mass). . . Take a chunk of
stuff. Two chunks stuck together have a larger mass according to a
scalar sum law. Blah blah you get the idea.

(For an operational definition of acceleration). . . . (d/dt)(dx/dt).
Vector. Blah Blah.......
DDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDDD


As students of the marvelous but seldom used Phys-L archives
<http://mailgate.nau.edu/archives/phys-l.html>
are aware, similar ground has been covered previously. In particular,
I previously indicated (Hake 2000a) a less "Blah Blah" analysis by
Arons'(1990) for defining inertial mass in term of operationally
defined F and a. In Socratic Dialogue Inducing (SDI) Lab #6 "Newton's
Second Law Revisited" (Hake & Wakeland 1997, Hake 2001) a force probe
and sonic motion detector are used to actualize the Arons experiment:
a force scale is calibrated in terms of the extension of a spring
attached to a standard body which undergoes various constant
accelerations on a horizontal runway. The inertial mass m of any
body is then operationally defined in terms of the ratio F/a.

But how many physics students (and even instructors) know the meaning
of "operational definition"? For an SDI Lab treatment (Hake 2001) of
operational definitions see SDI Lab #0.1 "Frames of Reference,
Position, and Vectors" (Hake 2001), especially "Operational
Definition of 'Position'" on page 10:

"To properly understand mechanics, it is necessary to appreciate the
meaning and significance of operational definitions (Holton & Brush
1985), defined as:

OPERATIONAL DEFINITION: a description which specifies the
experimental significance of a word or concept in terms of
well-defined measurement methods."

Operational definitions are revisited In SDI Lab #1, "Newton's First
and Third Laws," especially Sec. II "Operational Definitions" on
pages 7-11. These exercises represent a further attempt to get the
idea of operational definitions (OD's) across to university pre-meds
by means of Socratic discussions of OD's for "vertical,"
"horizontal," "force," "up," "down," and "equilibrium." Here we are
simply following Arons (1990).

Unfortunately, the OD aspect of science education is generally
ignored in current K-16 education, including that of AP physics
students and university physics majors (Hake 2000b).

As discussed by D.C. Phillips (2000) and Phillips & Burbules (2000),
operational definitions retain their crucial role in science (and
thinking generally), despite specious attacks from the
"antipositivist vigilantes."

Richard Hake, Emeritus Professor of Physics, Indiana University
24245 Hatteras Richard Street, Woodland Hills, CA 91367
<rrhake@earthlink.net>
<http://www.physics.indiana.edu/~hake>


REFERENCES
Arons, A.B. 1990. "A Guide To Introductory Physics Teaching" (Wiley,
1990), p. 52-55; reprinted with minor updates in "Teaching
Introductory Physics" (Wiley, 1997), p. 60-64.

Hake, R.R.. 1992. "Socratic pedagogy in the introductory physics
lab." Phys. Teach. 30, 546-552; version updated on 4/27/98 online at
<http://physics.indiana.edu/~sdi/>.

Hake, R.R. 2000a. "Re: N2" Phys-L post of 8 Jul 2000 11:24:30-0700: online at
<http://mailgate.nau.edu/cgi-bin/wa?A2=ind0007&L=phys-l&P=R10663>.

Hake, R.R. 2000b. "Is it Finally Time to Implement Curriculum S?"
AAPT Announcer 30(4), 103 (2000); on the web as ref. 13 at
<http://www.physics.indiana.edu/~hake> [CurriculumS.pdf., 3/15/01,
1200K] (400 references & footnotes, 390 hot-linked URL's). This
paper concerns improving the education of undergraduate physics
majors by instituting a "Curriculum S" for "Synthesis." But because
that's a small part of a much larger educational problem in the U.S.
there's a lot of material on the reform of P-16 education generally
(P = preschool).

Hake, R.R. 2001. Socratic Dialogue Inducing Labs; online at
<http://www.physics.indiana.edu/~sdi/> and also at the Harvard
Galileo server at <http://galileo.harvard.edu/> under "Hands On
Methods."

Hake, R.R. & R. Wakeland. 1997. "What's F? What's m? What's a?: A
Non-Circular SDI-TST-Lab Treatment of Newton's Second Law," in
"Conference on the Introductory Physics Course," Jack Wilson, ed.
(Wiley, 1997), p. 277-283.

Holton G. and S.E. Brush. 1985. "Introduction to Concepts and
Theories in Physical Science" (Princeton Univ. Press, 2nd ed., 1985)
p. 176-181. See also Holton & Brush (2001).

Holton G. and S.G. Brush. 2001. "Physics, the Human Adventure: From
Copernicus to Einstein and Beyond" (Rutgers Univ. Press), p. 161-162.

Phillips, D.C. 2000. "Expanded social scientist's bestiary: a guide
to fabled threats to, and defenses of, naturalistic social science."
Rowman & Littlefield.

Phillips, D.C. & N.C. Burbules 2000. "Postpositivism and educational
research." Rowman & Littlefield.