Harford Community College
Physical Science 106
Period of a Simple Pendulum Lab
Introduction
In order to understand the motion of a pendulum, one must analyze the
forces involved as we do using Newton's Laws of Motion. For the simple
pendulum, the forces depend on the angle of inclination of the mass attached to a
light string attached to a support as pictured below.
Forces on a simple pendulum.
In the diagram, the force of gravity mg acts vertically downward. This force may
be broken down into 2 forces, one parallel to the string and the other perpendicular.
The parallel force mgcos
simply pulls the string tight, and no motion occurs due
to this force.
Discussion Questions
1. What forces cancel and why?
2. Which force (refer to the diagram) moves the pendulum bob?
