A Barton's Pendulums device is a great tool for teaching students about resonance.1 Such a setup typically has several pendulums attached to a single string or solid support, where each pendulum is excited at a single frequency. The excitation can be produced by a large pendulum mass or by a motor. If a pendulum has a natural frequency that closely matches the excitation frequency, it swings with a large amplitude; otherwise, it does not. While these visual demonstrations are helpful, resonance behavior can be even better understood by graphically displaying the responses of oscillators to different excitations.
REFERENCES
1.
Monte M.
Giles
, “A resonance demonstration
,” Phys. Teach.
12
, 178
(March 1974
); http://faraday.physics.uiowa.edu/acoust/3A60.30.htm and http://www.fas.harvard.edu/∼scdiroff/lds/Oscillations Waves/BartonsPendulum/BartonsPendulum.html.2.
“Miniature Metal Gear Motor — 71 RPM” (http://www.hobby engineering.com). For the highest frequency shown, this motor required 7.2 V and 50 mA.
3.
Of course a more professional‐looking setup can easily be constructed, e.g., the motor can be held with a lab clamp.
4.
Timothy J.
Moran
, “Electricity: From tabletop to power plant
,” Phys. Teach.
47
, 18
–20
(Jan. 2009
);Timothy J.
Moran
, “Applications of sound spectrum analysis
,” Phys. Teach.
45
, 93
–95
(Feb. 2007
).
This content is only available via PDF.
© 2009 American Association of Physics Teachers.
2009
American Association of Physics Teachers
AAPT members receive access to The Physics Teacher and the American Journal of Physics as a member benefit. To learn more about this member benefit and becoming an AAPT member, visit the Joining AAPT page.
