The Leybold-Heraeus gravitational torsion balance is commonly used in undergraduate laboratories to measure the gravitational attraction between known masses to find the gravitational constant . Because the difficult task of data acquisition reduces its usefulness, we have implemented a simple design that minimizes this task and achieves more accurate results. This design features a small car that tracks the oscillating laser with the use of a stepper motor and some simple control circuitry. Step counting yields the location of the reflected laser in time.
REFERENCES
1.
Model number 33210: LD Didactic GmbH, Leyboldstrasse 1 D-50354 Huerth, Germany, www.leybold-didactic.com/data_e/.
2.
C. W.
Fischer
, J. L.
Hunt
, and P.
Sawatzky
, “Automatic recording for the Cavendish balance
,” Am. J. Phys.
55
, 855
–856
(1987
).3.
PASCO, 10101 Foothills Blvd., Roseville, CA 95747, www.pasco.com/
4.
Data Studio is Pasco’s interface software for their Science Workshop data acquisition equipment.
5.
See EPAPS Document No. E-AJPIAS-75-001703 for the data analysis Mathematica notebook. This document can be reached via a direct link in the online article’s HTML reference section or via the EPAPS homepage (http://www.aip.org/pubservs/epaps.html).
6.
Jon
Pellish
, Med
Webster
, and Jim
Waters
, “Gravitational torsion balance
,” Vanderbilt University, unpublished. Available at www.hep.vanderbilt.edu/∼webster/classes/p225lab/cavmain.pdf.© 2007 American Association of Physics Teachers.
2007
American Association of Physics Teachers
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