Purpose: To show the relationship between pendulum motion and waves

Introduction: In the two previous activities, you studied the motion of a pendulum. The pendulum's back-and-forth motion over the same path is mesmerizing. The repetitious motion tends to make me sleepy. This activity leads you to a very interesting connection between pendulum motion and waves. The procedure is messy, but fun.

Materials: paper cup, string, sand or fine dirt, paper, pencil, old newspapers & cellophane or masking tape

Procedure:

1. Read all steps of this procedure before you begin the activity. You will need a family member or friend to help you.

2. Use your pencil or pen to punch a small hole in the bottom of the paper cup. From the outside of the paper cup, cover the hole with tape. The cup will be your pendulum bob, and it will later be filled with sand or dirt.

3. Tape three long strings to the cup to form a funny-looking pendulum. Check the lengths of the strings. You will want the pendulum to just barely move over the floor. The distance between the swinging pendulum and the floor should be about one inch. Use a pencil, as before, to suspend your pendulum from the table or other support.

4. Spread old newspaper in the area in which the pendulum will swing. This activity can be messy.

5. Tape four pieces of notebook paper end-to-end to form one long, narrow paper. Place one of the ends of the taped paper under the pendulum.

6. Now this is the tricky part. Read this step carefully. Fill the paper cup with sand or fine dirt. Remove the tape from the bottom of the cup. The sand or dirt should begin to sift out of the cup much like sand moves out of an hourglass. Quickly set the pendulum in a swinging motion. The swing path should be no larger than the width of the paper. As the pendulum is swinging, slowly and gently move the paper under the pendulum. The notebook paper is to be pulled perpendicular to the swinging of the cup. The paper should be pulled continuously in that direction and fast enough to not let the sand overlap on itself. As you pull the paper the sand or dirt will form a pattern on the paper.

7. Answer the questions.

8. Clean the area.

9. Submit this assignment according to the directions at the end of the activity.

6.02 Discussion Question:

Go to the discussion area and post an answer to this question. Respond to at least one other person and explain why you agree or disagree with their comment.

1. Describe the pattern formed by the dirt on the paper.

2. Where have you seen a pattern like this before? Explain.