This project is from spring 2007. Its really fun to plan, build and use.
You make a cone to hold fine sand or (we used) salt. It must be constructed and hung so that it can swing freely in every direction. The bottom or narrow end of the cone needs to have just the right size hole to let the salt leak out in a fine line. We recommend laying down black paper to contrast the white salt. Its also good for clean up - if you use the bare floor and sweep your salt up each time you tend to get dirt and dust in it and the salt does not flow as evenly the next time.

We suggest that you brainstorm ahead of time about how to build your pendulum: discuss 1.) materials, 2.) string length and attachment from the cone upward, 3.) size of cone hole, 4.) distance between bottom of pendulum and floor. Make predictions then test them out! You'll be surprised at how much it effects your pendulum. Don't get frustrated if it doesn't work the first time. We had to make several alterations before we got it right. Good Luck!