Description of the Pendulum
A pendulum is a weight suspended from a pivot so that it can swing freely. When a pendulum is displaced sideways from its resting, equilibrium position, it is subject to a restoring 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 period depends on the length of the pendulum, and also to a slight degree on the amplitude, the width of the pendulum's swing.
The simple gravity pendulum is an idealized mathematical model of a pendulum. This is a weight on the end of a massless cord suspended from a pivot, without friction. When given an initial push, it will swing back and forth at constant amplitude. Real pendulums are subject to friction and air drag, so the amplitude of their swings declines.
The load undergoes terrestrial acceleration on the one hand and the horizontal acceleration of the trolley on the other hand; it is thus subject to a pendula movement and swaying in accordance with the following simplified expression as left.