The draining of a water column through a vertical discharge capillary tube is examined with the aid of a force sensor. The change of the mass of the liquid in the column with time is found to be not purely exponential as implied by Poiseuille’s law. Using observed residuals associated with a kinetic energy correction, an approximate formula for the mass as a function of time is derived and excellent agreement with experimental data is attained. These results are verified by a viscosity test of distilled water at room temperature. A simple and inexpensive weight-controlled capillary viscometer is proposed that is especially suitable for undergraduate physics and chemistry laboratories.
REFERENCES
1.
2.
J. R.
Smithson
and E. R.
Pinkston
, “Half-life of a water column as a laboratory exercise in exponential decay
,” Am. J. Phys.
28
, 740
–742
(1960
).3.
G. T.
Hageseth
, “Surface and kinetic energy densities: A fluid dynamics laboratory exercise
,” Am. J. Phys.
54
, 1011
–1014
(1986
).4.
L. C.
Cerny
, “Absolute viscosity of water, a student experiment
,” Am. J. Phys.
29
, 708
–709
(1961
).5.
T. B.
Greenslade
, “Simulated secular equilibrium
,” Phys. Teach.
40
, 21
–23
(2002
).6.
S. J.
Fairman
and T. A.
Walkiewicz
, “Fluid flow with Logger Pro
,” Phys. Teach.
41
, 345
–349
(2003
).7.
S. H.
Maron
, M. I.
Krieger
, and A. W.
Sisko
, “A capillary viscosimeter with continuously varying pressure head
,” Am. J. Phys.
25
, 971
–976
(1954
).8.
C. E.
Synolakis
and H. S.
Badeer
, “On combining the Bernulli and Poiseuille equation—A plea to authors of college physics texts
,” Am. J. Phys.
57
, 1013
–1019
(1989
).9.
M. R.
Cannon
, R. E.
Manning
, and J. D.
Bell
, “Viscosity measurement: The kinetic energy correction and a new viscometer
,” Anal. Chem.
32
, 355
–358
(1960
).10.
J. V.
Sengers
and F. T. R.
Watson
, “Improved international formulations for the viscosity and thermal conductivity of water substance
,” J. Phys. Chem. Ref. Data
15
, 1291
(1986
).© 2005 American Association of Physics Teachers.
2005
American Association of Physics Teachers
AAPT members receive access to the American Journal of Physics and The Physics Teacher as a member benefit. To learn more about this member benefit and becoming an AAPT member, visit the Joining AAPT page.
