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Author: Janice VanCleave

So You Want to Do a Project about Pendulums!

Let's Explore


To determine the frequency of a pendulum.


  • Pencil
  • Transparent tape
  • I6-inch (40-cm) piece of string
  • Metal washer
  • Helper


  1. Lay the pencil on a table so that about half the pencil extends over the edge of the table, eraser end out. Secure the pencil to the table with tape.
  2. Tie one end of the string to the washer, and then tie the other end of the string around the free end of the pencil. You have made a pendulum.
  3. Use your hand to lift the washer to one side so that it is level with the pencil and the string is straight.
  4. Ask your helper to time 10 seconds. When your helper says "go," release the washer and let it fall. Count the number of swings (a swing is one complete back-and-forth motion) until your helper says "stop." If the final swing is three-fourths or more of a full swing, count it as one swing.
  5. Record the number of swings in a Pendulum Data table like the one shown.
  6. Repeat steps 3 to 5 three or more times. Average all the tests.



The author's pendulum averaged 9 swings.


The hanging string and washer is a pendulum. A pendulum is a weight hung by a rod or string from a fixed point in a way that allows the weight to swing back and forth freely. Every pendulum has a natural frequency (number of times a regularly repeating event, such as a pendulum moving back and forth, occurs per second) at which it swings when moved.

For Further Investigation

Would a longer string make the pendulum swing slower? A project question might be, Does the length of a pendulum affect its natural frequency?

Clues for Your Investigation

  1. Prepare two more pendulums, one 10 inches (25 cm) and the other 24 inches (60 cm) long.
  2. Repeat the original investigation, counting the swings of each pendulum in 10 seconds.


References and Project Books

Doherty, Paul, and Don Rathjen. The Spinning Blackboard and Other Dynamic Experiments on Force and Motion. New York: Wiley, 1996.

Franklin, Sharon, and Mary Leontovich. Force, 0/ Course! Glenview, Ill.: Good Year Books, 1995.

Hann, Judith. How Science Works. Pleasantville, NY.: Reader's Digest, 1991.

Melton, lisa Taylor, and Eric Landizinsky. 50 Nifty Science Experiments. Chicago: Lowell House, 1992.

Potter, Jean. Science in Seconds/or Kids. New York: Wiley, 1995.

VanCleave, Janice.]anice VanCleave's Physics/or Every Kid. New York: Wiley, 1991.

Janice VanCleave's 200 Gooey, Slippery, Slimy, Weird, and Fun Experiments. New York: Wiley, 1993.

Wiese, Jim. Roller Coaster Science. New York: Wiley, 1994.

Wood, Robert W. Mechanics Fundamentals: Funtastic Science Activities/or Kids. New York: Learning Triangle Press, 1997.

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