1 Skills, Methods, and the Nature of Physics - BC Science Physics 11

Investigation 1-4 Making a Pendulum Clock
Purpose
To learn how a pendulum can be used as a clock
Procedure
1. Prepare a simple pendulum by tying a string to a pendulum bob, either a large washer, as in Figure 1.4.6, or
a drilled metal ball. Feed the string through the opening of the pendulum support. Avoid winding the string
around the support rod. If you do this, the length of the pendulum changes during a swing.
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Figure 1.4.6 Setup for Investigation 1-4
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2. Start by adjusting the length l of the pendulum so that it is as close to being 10.00 cm as you can make it.
Measure l from the bottom of the pendulum clamp to the centre of the bob, as shown in Figure 1.4.6.
3. Push the bob a small distance, about 2 cm, to one side and let it swing freely. To get a rough idea of how long
the pendulum takes to make one swing, use a stopwatch to measure the time it takes for the bob to swing
from the highest point on one side of the swing to the highest point on the other side, then back to its starting
position. The time it takes the pendulum bob to complete a full swing like this is called the period (T) of the
pendulum. Try measuring the period of one swing several times with your stopwatch. Why do you think your
measurements are so inconsistent?
4. To obtain a more reliable measurement of the period of the pendulum, you will now measure the time for
a large number of swings (50) and find the average time for one swing by dividing by 50. Set your 10.00 cm
pendulum swinging through a small arc, as before. Start counting backward (3, 2, 1, 0, 1, 2, 3, 4, etc.) and start
your stopwatch at 0. Stop your watch after 50 swings and record the time your pendulum took to complete
50 swings.
5. To figure out the period of the pendulum, divide the time for 50 swings by 50.0. Record the period, T, in a table
like Table 1.4.3. Check your result by repeating the measurement. If necessary, repeat a third time.
© Edvantage Interactive 2012 ISBN 978-0-9864778-3-6 Chapter 1 Skills, Methods, and the Nature of Physics 31