In his Phys-L post of 11 Feb 2002 08:55:21-0800,titled "Re:
Supporting vs stifling curiosity," Larry Woolf wrote:
This common misconception . . . (that water will ALWAYS rotate
counterclockwise - as observed from above - down a drain in the
northern hemisphere). . . is prevalent in elementary and middle
school science books . . . (in the U.S.). . . Refer your teacher to
the following site:
<http://www.ems.psu.edu/~fraser/Bad/BadCoriolis.html>.
On the other hand, the misconception that the Coriolis force is so
small that its effects cannot possibly be observed in draining
bathtubs is prevalent among physics-department faculty in the great
research universities of the U.S.
At refs. 1-5, there are references to more detailed information on
Coriolis effects on draining water than is available at Alistair
Fraser's excellent website <http://fraser.cc/index.html>, in
particular
The last is for the benefit of PhysLrnR Dewey Dykstra and other
pipers who may wish to study the rotation of smoke plumes in and out
of bag pipes.
As pointed out in ref. 1b:
A. Water from a bathtub in the NORTHERN-hemisphere was consistently
observed to rotate in a COUNTERCLOCKWISE (as observed from above) by
Shapiro (2) at MIT.
B. Water from a bathtub in the SOUTHERN-hemisphere was consistently
observed to rotate in a CLOCKWISE (as observed from above) by
Trefethen et al. (3) at the University of Sydney.
Now "A" & "B" are, of course, as expected if the direction of
rotation is determined by the Coriolis force. Quoting from ref. 1b:
"The heroic efforts required for these bathtub-vortex observations
are summarized by Walker, (4) but are well worth reading in the
original. For the less heroic, or those averse to the splinters of
wooden bathtubs, (3) a plastic-pail bathtub may be placed on a
merry-go-round with an angular velocity omega of about 10^4 greater
than that of the Earth. Merry-go-round rotations simulating northern
and southern hemispheres then result in water vortices around the
drain that are, respectively, consistently counterclockwise and
clockwise. This experiment can be performed by introductory-course
students (5)."
Richard Hake, Emeritus Professor of Physics, Indiana University
24245 Hatteras Street, Woodland Hills, CA 91367 (where bathtubs
always drain counterclockwise)
<rrhake@earthlink.net>
<http://www.physics.indiana.edu/~hake>
REFERENCES
1. (a) J.W. Hanneken, "Coriolis myths and draining bathtubs," Am. J.
Phys. 62, 1063 (1994); (b) R.R. Hake, "More on Coriolis myths and
draining bathtubs," ibid.; (c) C. Robertson, "Still more on Coriolis
myths and draining bathtubs - films and video tapes," ibid.
2. A. H. Shapiro, "Bathtub Vortex," Nature 196, 1080 - 1081 (1962);
film Vorticity, Educational Services, Inc., Watertown, Mass., 1961);
film loop #FM-15, The Bathtub Vortex, ibid., 1963.
3. L.M. Trefethen, R.W. Bilger, P.T. Fink, R.E. Luxton, and R.I.
Tanner, "Bathtub Vortex in the Southern Hemisphere," Nature 207, 1084
- 1085 (1965).
4. J. Walker, "The Flying Circus of Physics" (With Answers) (John
Wiley & Sons, New York, 1975) p. 95. Walker gives other references
germane to the experiments.
5. R.R. Hake, Socratic Dialogue Inducing (SDI) Lab #3 "Circular
Motion and Frictional Forces, online at
<http://www.physics.indiana.edu/~sdi>. A Teacher's Guide (password
protected) is online (password protected) at the Harvard Galileo site
<http://galileo.harvard.edu/> under Hands-On Methods/SDI
Labs/Resources/Teacher's Guides, where "/" means click on the
following text.
SDI labs (see, e.g., ref. 6) are among the more effective
interactive-engagement methods (for a partial listing see ref. 8),
are freely available on the web, but are sadly neglected by physics
teachers and rarely mentioned by physics-education researchers.
Possible reasons for the unpopularity of the Socratic method and SDI
labs have been given (7).
6. R.R. Hake, "Socratic pedagogy in the introductory physics lab,"
Phys. Teach. 30:546-552; updated version (4/27/98) online at
<http://physics.indiana.edu/~sdi/>.
8. Hake, R.R. 2002. "Lessons from the physics education reform
effort." Conservation Ecology 5(2): 28; online at
<http://www.consecol.org/vol5/iss2/art28>, especially the section
"Popular interactive engagement methods." "Conservation Ecology," is
a FREE "peer-reviewed journal of integrative science and fundamental
policy research" with about 11,000 subscribers in about 108
countries. Volume 5, issue 2
<http://www.consecol.org/Journal/vol5/iss2/index.html> contains a
special feature on "Interactive Science Education."