3A50.XX Damped Simple Pendulum


Damped harmonic oscillator, eddy currents


A strong permanent magnet acts as a simple pendulum, swinging back and forth while hanging from strings. A copper plate underneath the magnet can be moved up to tune the eddy current damping.



  • [1] Magnet on strings
  • [1] Copper plate on a wooden block
  • [1] Lab jack
  • [1] Lab stand
  • [1] 90-degree clamp
  • [1] Aluminum rod

Classroom Assembly

  1. Clamp rod to lab stand.
  2. Hang magnet on rod.

Important Notes

  • Danger! Strong magnets may disrupt pacemakers!
  • Strong magnets can pinch fingers.
  • Strong magnets may erase magnetic memory and magnetic stripes on credit cards.


  1. Swing the magnet to show the undamped motion.
  2. Place the lab jack and copper plate under the magnet.
  3. Swing the magnet to show the damped motion.
  4. Adjust the lab jack height for a different level of damping and repeat.


Additional Resources


  • PIRA 3A50.XX


  • Don't attempt this at home!

Last revised

  • 2020


Related AV

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If you have any questions about the demos or notes you would like to add to this page, contact Ricky Chu at ricky_chu AT sfu DOT ca.