Instructions for Constructing a Pendulum

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Pendulums are utilized in a variety of ways, including clocks, music timing devices, experiments, and art. The most well-known form of pendulum is the Foucault pendulum, named after its inventor, Leon Foucault, which would swing all day but appeared to rotate slowly in a circle instead of swinging in the same direction. This proved that the Earth rotates [source: Science Daily].

Although the original Foucault pendulum was very large, you can create a smaller version of it. However, you will need to do this outdoors on a calm day. Here are the materials you will require:

  • Cloth or canvas sack
  • Fine, dry sand
  • Large garbage bag
  • Nail
  • Nylon cord, 13 feet (4 meters) long
  • Tall stable structure, such as a 12-to-15 foot (3.7-to-4.6 meter) ladder or swing set
  • Tape

Here’s how to make a Foucault pendulum:

  1. Fill the sack with sand.
  2. Check that the sack has no holes by lifting it up and gently shaking it.
  3. Seal the sack with the cord.
  4. Hang the sack from the high structure.
  5. Poke a hole in the bottom of the sack with the nail. Make the hole a little larger than the tip of a pen, so the sand doesn’t come out too quick. Check the rate of flow, and adjust the size of the hole if necessary.
  6. Seal the hole with tape.
  7. Spread a garbage bag under the pendulum, so it covers the surrounding area.
  8. Check that the sack is hanging straight down. Adjust the cord or sack if necessary.
  9. Pull the sack back while keeping the cord taut until it’s around 4 feet (1.2 meters) above the ground.
  10. Remove the tape from the hole and carefully start the pendulum swinging in a straight line. It shouldn’t swing in an ellipse.
  11. Let the sack swing for an hour, gently pushing the cord whenever it starts slowing down. Be careful to push it in the direction of the swing; don’t shift or redirect the cord.
  12. Watch the sand traces on the garbage bag — each trace should be slightly offset from the previous one. The direction and distance between each trace depends on the hemisphere and latitude of your location [source: Foucault Pendulum].

Be patient; it may take several attempts to get it just right.


1. What is a pendulum?

A pendulum is a weight suspended from a fixed point that swings back and forth due to the force of gravity. It is commonly used in clocks as a timekeeping device.

2. What materials do I need to build a pendulum?

You will need a weight, a string or rod to suspend the weight from, a fixed point to hang the string or rod from, and a surface to mount the pendulum on.

3. How do I choose the weight for my pendulum?

The weight of your pendulum should be determined by the length of the string or rod you are using. The longer the string or rod, the heavier the weight should be to maintain a consistent swing.

4. How do I attach the weight to the string or rod?

You can attach the weight to the string or rod using a hook or by tying a knot. Make sure the weight is securely attached and balanced.

5. How do I determine the length of the string or rod?

The length of the string or rod should be determined by the desired swing time of the pendulum. The longer the string or rod, the slower the pendulum will swing.

6. How do I mount the pendulum?

You can mount the pendulum on a sturdy surface using screws or adhesive. Make sure the surface is level and stable.

7. How do I set the pendulum in motion?

To set the pendulum in motion, simply pull the weight to one side and release it. The pendulum will swing back and forth in a consistent motion.

8. How do I adjust the swing of the pendulum?

You can adjust the swing of the pendulum by changing the weight, length of the string or rod, or by adjusting the position of the fixed point.

9. What factors affect the swing of the pendulum?

The swing of the pendulum is affected by gravity, the weight of the pendulum, the length of the string or rod, and the position of the fixed point.

10. Can I use a pendulum for anything besides timekeeping?

Yes, pendulums can be used in a variety of scientific experiments, such as measuring the acceleration due to gravity or determining the properties of materials.

11. How do I care for my pendulum?

Keep your pendulum clean and free of dust. Check the weight and string or rod periodically to ensure they are secure and balanced. If the pendulum is not swinging properly, check for any obstructions or changes in the environment that may be affecting its motion.

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