The simple pendulum has long been used to measure g, the acceleration due to gravity, with a precision of a few percent. Achieving agreement with the accepted value of less than 1% is feasible in the high school laboratory, though it requires some care.1 The precision of the measurement is bound by how accurately the period and the pendulum length are determined. To improve on the period measurement, we have developed a simple and inexpensive method using a magnet and telephone pickup.2
REFERENCES
1.
Parker
Moreland
, “Improving precision and accuracy in the g lab
,” Phys. Teach.
38
, 367
–369
(Sept. 2000
).2.
We purchased the telephone pickup at RadioShack (item # 44–533) for $7.99.
3.
Soundcard Oszilloscope version 1.24, by Christian Zeitnitz, may be downloaded at zeitnitz.de/Christian/Scope/Scope_en.html subject to the author's terms of usage.
4.
The time between two consecutive pulses is only half the period and must be doubled. Alternatively, the time from one pulse to the third in a series gives a direct measure of the period.
5.
For a discussion of the error associated with measuring the length of a pendulum, see
Randall D.
Peters
, “Student‐friendly precision pendulum
,” Phys. Teach.
37
, 390
–393
(Oct. 1999
).6.
We inserted our latitude and elevation into the formula found in Wolfgang Torge, Gravimetry (Walter de Gruyter, Berlin, 1989), Chap. 3.
7.
For another “computerized” pendulum experiment, see
T. J.
Bensky
, “Measuring g with a joystick pendulum
,” Phys. Teach.
39
, 88
–89
(Feb. 2001
).
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