Editing Procedure (section)

=== Period Measurement ===
[[File:CNUPendulum.jpg|thumb|40px]]
A photo-gate is a good way to measure periods of the pendulum as it swings. Considerations for the photo-gate include a rigid base for it to stand on, what part of the pendulum is breaking the beam, and what software is interpreting the photo-gate signal.

A solid base is necessary so that movement around the apparatus and natural vibrations of the lab do not cause unwanted motion of the gate.

Something other than the bar, which is approximately 2.5 cm thick, should break the photo-gate beam. A thin steel "needle" was fashioned to be attached to each end of the pendulum and can be seen in the image. This allows for much small oscillations meaning that the small angle approximation correction can be much smaller. Another point to consider is the distance from the pivot to the photo-gate. The angle of oscillation should be measured so that the data can be corrected for the small angle approximation. The distance the pendulum should be displaced can be calculated by:

: <math>x = y \tan \theta </math>

Where <math>y</math> is the distance from the pivot to the photo-gate, <math>\theta</math> is the desired angle of oscillation, and <math>x</math> is the horizontal distance the pendulum should be displaced '''at the height of the photo-gate.'''

The software easily available at CNU for interpreting the photo-gates is DataStudio. DataStudio has a photo-gate pendulum setup but use caution as the software interpolates the period based on your reported pendulum thickness. This setting can be used as a rough estimate of the period but using the state setup and taking time from either the leading or trailing edge of the data spikes is preferred.