Tech Support: Pendulum



Helpful Tips

  • There is no need to remove the washers from the string when you are testing the mass variable. Simply remove the string from the hanger slot and let the excess washers hang over the back of the pendulum. The cord stop device will keep the washers from falling off the string.
  • When you use the photogate with the pendulum, please remember that you must have the timer in period mode, and then you must multiply the resulting number of seconds by 2 to get the true period of the pendulum. This is because the bob will break the beam twice in one cycle, and the timer will only ready the time it takes the bob to go ½ of a cycle. Thus, when you multiply the timer readout by 2, you will have the correct time for one complete cycle of the pendulum, which is the period.
  • If students are having trouble getting the pendulum to swing clearly through the photogate without hitting it, have the bob releaser stand to the side and "sight" the bob through the gate before releasing it. It is much easier to get the bob to swing cleanly through the gate. A little practice goes a long way!
  • In order for you to use the Pendulum with a photogate, you must attach the photogate to the physics stand with a black female knob.
  • Set your Timer to period mode.


Q: Can you use the pendulum without the timer and photogate?

A: Yes. Students can actually use a regular clock second hand or a stopwatch to time the pendulum. The results will not be as accurate, but for younger students, the accuracy will be sufficient.

Q: Why is the pendulum featured in the sound and waves portion of the Foundations of Physical Science curricula? Isn't this a basic motion/energy demonstration?

A: The pendulum provides a great opportunity for students to work with harmonic motion vocabulary that can be confusing. Words like "cycle", "period", and "amplitude" are demonstrated very nicely by working with the pendulum. The pendulum is also a wonderful example of potential to kinetic energy conversions, and can be used to demonstrate and study those concepts as well.