The word “pendulum” comes from the Latin word “pendulus” which means “hanging”. A pendulum is an object hanging from a fixed point that when pulled back and released, swings freely. A pendulum swings due to gravity and inertia. Gravity pulls the pendulum toward the center of the Earth and inertia causes a moving pendulum to continue moving, or a pendulum at rest to remain still.
Galileo became interested in investigating pendulums as he watched a lamp swinging in a cathedral in Pisa, Italy while he was a university student. In 1602, he began experimenting with pendulums and discovered that the period of a pendulum is not affected by the amplitude. Galileo had the idea that a clock could be made using a pendulum, and made plans to build one, but he never did. In 1665, a Dutch scientist named Christiaan Huygens was the first person to create a clock using a pendulum. It is said that his clock was accurate, only losing one minute per day, which was quite an accomplishment. He later improved the clock further so that it only lost 10 seconds per day.
Pendulum Parts and Vocabulary:
Some important terms to know when working with a pendulum are: cycle (or period), amplitude (or arc or pullback distance) and frequency. A cycle or period is defined as one swing, including the both the trip out and the return swing. The frequency is the number of cycles that occur in a period of time. These terms are important when discussing the various experiments that can be done with a pendulum. The amplitude is the angle at which the bob is released.
Experimenting with a Pendulum:
A pendulum makes an interesting object of scientific study as there are several simple variables with which to experiment. The results might be unexpected to those that are not familiar with the behavior of a pendulum. Not only does a pendulum provide a method in which to study physics, but it also provides a way to apply and gain experience with the scientific method.
See my article on “experiments with pendula” for more information.