Shadow projection of circular motion

Purpose: Describe Simple Harmonic motion as projection of circular motion.


  • Turntable
  • Ball with a metal stand(cylinder)
  • Pendulum


Keep the ball on the metal cylinder and place it on the turntable as shown in the picture.  Adjust the height of the pendulum, so that two balls are in same vertical level. Start the rotating platform, release the pendulum from a certain height so that the shadow of both will move almost together. Watch the shadow of these motions.