FUNCTIONS EXPERIMENT
PENDULUM
Introduction
For a pendulum swinging back and forth, the amount of time required to complete one full
swing is called the period. Galileo discovered that the period depends only on the length
of the pendulum and the acceleration due to gravity. In fact, the period and the length of
the pendulum are related by a power function. In this lab we will establish the relationship
between the period and the length of the pendulum by measuring the period for differing
lengths.
Equipment and Setup
For this experiment you will need a TI calculator with the Vernier PHYSICS program loaded,
a CBL unit, a motion detector, and a pendulum.
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18"motion detector
books stand
swinging pendulum
Set up the pendulum as shown above. Place the motion detector facing the path of the
swinging pendulum. The detector will not measure objects within 18 inches, so be sure to
set it at least 18 inches from the widest point of the arc. You may need to set the motion
detector on a stack of books to get the pendulum directly in the path of the detector. To set
up the CBL unit to record measurements, first plug the motion detector into SONIC on the
CBL unit and turn the CBL unit on. Select the PHYSICS program on the calculator. In the
home menu choose SET UP PROBES. When asked for the number of probes, enter 1. In
the next menu choose MOTION. The screen will display the home menu again. Now select
COLLECT DATA, and choose TIME GRAPH. Set the calculator to take 150 measurements
0.05 second apart. The calculator will then ask if you want to change the setup or continue.
The next screen will notify you that the calculator is ready to begin taking measurements.
Procedure
When the calculator is ready to begin taking measurements, gently swing the pendulum
in the direction of the motion detector. Note that the pendulum will swing out of the
vertical range of the motion detector if the pendulum swings too high. Press ENTER on the
calculator to begin taking measurements. The calculator will then display the graph of the
distance of the pendulum from the motion detector versus time. Depending on the length
of the pendulum, you should see between three and five periods. Repeat the procedure until
you get a satisfactory graph.
