An important concept in physics is simple harmonic motion – the periodic motion of a mass with a restoring force proportinal to its displacement. This force might come from gravity, a spring, or many other sources, but the same mathematics describes their motion. We have many demonstrations of simple harmonic motion (or SHM) in our collection, including G1-01 and G1-52, which you can see in action in this video starring UMD PhD student Subhayan Sayu.
You can experiment with this at home! Any mass on a spring or on a string or rolling in a well can be a pendulum. Or, try out these Periodic Motion simulations at the PhET Collection: Pendulum Lab or Masses and Springs.
The University of Cambridge offers an example of a simple pendulum experiment to try at home; check it out at https://nrich.maths.org/5376