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Pendulums have many applications, from clocks to musical timing devices, experiments, and even in art! The Foucault pendulum, named after its inventor Leon Foucault, is the most well-known. Unlike typical pendulums that swing in one direction, it appears to rotate in a slow circular motion throughout the day. This demonstrated the Earth's rotation [source: Science Daily].
While the original Foucault pendulum was massive, you can create a miniature version. Just make sure to do it outdoors on a calm, windless day. Here's what you'll need:
- Cloth or canvas bag
- Fine, dry sand
- Large trash bag
- Nail
- 13 feet (4 meters) of nylon cord
- A tall and sturdy structure, like a 12-to-15 foot (3.7-to-4.6 meter) ladder or a swing set
- Adhesive tape
Follow these steps to build a Foucault pendulum:
- Fill the sack with sand.
- Lift the sack and gently shake it to ensure there are no holes.
- Tighten the sack with the cord.
- Hang the sack from the tall structure.
- Use the nail to create a hole at the bottom of the sack. Make sure the hole is slightly bigger than a pen tip so that the sand flows slowly. Observe the flow and adjust the hole size as needed to achieve a steady, slow stream.
- Cover the hole with tape to stop the sand from spilling out.
- Place a garbage bag beneath the pendulum to cover the area around it.
- Make sure the sack is hanging straight down, adjusting the sack or cord if needed.
- Pull the sack back, keeping the cord taut, until it’s about 4 feet (1.2 meters) from the ground.
- Carefully remove the tape from the hole and start the pendulum swinging in a straight line. Ensure it does not swing in an elliptical shape.
- Allow the sack to swing for about an hour, gently pushing the cord when it begins to slow. Make sure to push in the direction of the swing, without altering the angle of the cord.
- Observe the sand traces on the garbage bag — each one should be slightly off-center from the previous one. The direction and spacing of the traces will vary depending on your location's hemisphere and latitude [source: Foucault Pendulum].
Take your time; it may require several attempts to perfect it.
