Construction Details of a Home-Made Foucault Pendulum.

The aim is to build a working Foucault pendulum (to demonstrate the rotation of the earth on its axis) using materials from a modern American mall. The pendulum, mounted on a 4 foot ladder, is shown at the right.

The two main engineering problems are:

1) Replacing the energy lost (mostly due to wind resistance) so that the pendulum continues to swing without "dying down." If this is not done, for a pendulum of ordinary size, the swing comes to a stop before the earth has had time to rotate significantly, and the evidence for the rotation is lost.

2) Ensuring that the pendulum will swing with equal ease in all directions. Without special care a pendulum has a preferred direction of swing. When its plane of oscillation arrives at a preferred direction, the pendulum tends to stay there, and evidence for the earth's rotation is lost.

For discussion of the two problems, click on the problem number.

The pendulum bob can be connected to the pivot in a number of ways. One is shown here.

The process of matching the natural frequency of the pendulum to the frequency of the square wave requires adjusting the length of the pendulum, much as old fashioned grandfather clocks were regulated. Click here to see a description.

For a more thorough discussion of the short, driven, Foucault Pendulum, and live snapshots of its motion, visit the Millersville University Physics website.