When a pendulum is displaced from its resting equilibrium position, it is subject to arestoring force due to gravity that will accelerate it back toward the equilibrium position. When released, the restoring force combined with the pendulum’s mass causes it to oscillate about the equilibrium position, swinging back and forth. The time for one complete cycle, a left swing and a right swing, is called the period.
The photograph was taken by Louis Dallara at the Franklin Institute, Philadelphia, PA
The photo is submitted to http://www.photofriday.com/