The Berry Pendulum seen from the side. (image credit: Todd Timberlake)
The Berry College Foucault Pendulum was installed in the atrium of McAllister Hall when the building opened in January 2001. The pendulum has a total length of about 16 meters with a 107-kg bob. At that length, the pendulum swings back and forth about every 8 seconds. The plane of the pendulum's oscillation precesses clockwise, taking about 42 hours to precess a full 360 degrees.
Just below the pendulum is a sand pit. A pin placed in the bottom of the pendulum bob traces the path of the pendulum's motion in the sand, making it easier to see the precession. A circular rail encloses the pendulum's oscillation area, while another larger rail extends farther out to prevent visitors from getting too close to the pendulum, since touching the pendulum disrupts the pendulum's motion and could lead to injury.
Air resistance and the drag of the pin in the sand will cause to the pendulum to slow down over time and eventually stop oscillating. To maintain the oscillation the Berry Pendulum has a drive motor located at the pivot point. This motor sustains the pendulum's oscillatory motion without altering the precession of the plane of oscillation. A malfunction in the motor caused the pendulum to stop precessing when it reached a certain orientation (but only if the motor was on). Funds were raised through a crowdfunding campaign in late 2020 and the motor was repaired in early 2021.
