3A40.10 Circular Motion vs. Mass on a Spring


Simple harmonic motion, uniform circular motion


The shadow projections of uniform circular motion and simple harmonic motion look identical when the periods of the respective motions are the same. The moving objects are a ping pong ball on a turntable and a mass hanging from a spring.



  • [1] Turntable with ping pong ball
  • [1] Lab stand
  • [1] 90-degree clamp
  • [1] Aluminum rod
  • [1] Hook clamp
  • [1] Lab jack
  • [1] 100 g mass
  • [1] Pasco spring
  • [1] DC power supply (at least 20 V, 1 A)
  • [1] DMM
  • [4] Banana cable
  • [1] Desk lamp
  • [1] Viewing screen
  • [1] Power bar

Classroom Assembly

  1. Assemble a stand for the 100 g mass by attaching the hook clamp to the aluminum rod, then clamping the rod to the lab stand.
  2. Use the banana cables to connect the turntable to the DC power supply and DMM.
  3. Set up the viewing screen.
  4. Align the turntable and mass in front of the desk lamp to get a suitable silhouette.
  5. Tune the DC power supply voltage until the periods of motion for the turntable and spring are the same. Start searching around 15.5 V.
  6. Turn off the desk lamp and DC power supply.


  1. Turn on the desk lamp and the DC power supply.
  2. Start the oscillation of the mass in phase with the ping pong ball.
  3. Turn off the desk lamp and the DC power supply.


Additional Resources


  • PIRA 3A40.10


  • Don't attempt this at home!

Last revised

  • 2019


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.