Pendulums
Teacher’s Guide
by: Jeff Molitor (Idaho State University)
Lesson Overview: Introduce the idea of a pendulum and have the students
discover what factors influence the period of the pendulum.
National Science Education Standards Addressed:
1. List them here
Subject area(s): Physics
Resources:
1. Information on pendulums
a. http://hyperphysics.phy-astr.gsu.edu/hbase/pend.html
b. http://hyperphysics.phy-astr.gsu.edu/hbase/pendl.html#c1
Suggested time: 1 hour
Topic: Pendulums
Audience: 5th-6th
Materials:
 String
 Metal Washers
 Stopwatch
 Tape
Learning Objectives:
Students will:
1. Learn what a pendulum is
2. Identify the factor(s) that effect the period of a pendulum.
Background:
1. Gives students an opportunity to explore a physical phenomenon and determine through
experimentation the factors that affect the pendulum.
2. Pendulums, in various forms, are found in clocks, swing sets, metronomes, and seismometers, just
to name a few.
Assessment Strategy:
1. Students will need to hypothesize, analyze, and form their own conclusions about the results
of the experiment.
Teaching Tips:
Since the primary focus of this activity is experimenting with different factors of the pendulum the majority of
the time will need to be spent letting the students experiment. However, some primary information needs to be
discussed.
The most important topic is the definition of period. The period is the time it takes for the pendulum to go from
the starting position, then down and back to the same position. This is one complete cycle of the pendulum.
For example, the period of the pendulum used in a clock will be one second because the pendulum is the device
that regulates the clock.
Idaho State University’s GK-12 Project
http://www.isu.edu/%7Esanghann/Index.html
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At this point a short discussion could be initiated where the students indentify different places where they have
seen a pendulum. The students should be able to identify the period, not necessarily a numerical value. This
discussion can then lead into the factors of a simple pendulum that change its period. The students should try to
come up with these factors on their own, if not the teacher should try to ask questions to lead the students to the
following factors: length of the string, weight of the bob.
The experiment can then be introduced.
Preparation:
The only preparation required for this experiment is to tie a washer to the end of a string and ensure that there
are enough for each group, which will consist of no more than two students.
Experiment:
This experiment will consist of four experiments with 3 trials minimum for each. The students will measure the
period of a pendulum by changing the length of the string and also by changing the weight of the bob. Only one
factor should be changed per experiment so that students will be able to see how the different factors affect the
period. The suggested trials are listed below:
1. Pendulum unaffected
2. Shortened string length, original bob weight
3. Original string length, additional washers
4. Shortened string length, additional washers
The students should write down a hypothesis on whether the string length or additional weight will affect the
period of the pendulum.
The string should be marked at the two lengths so that the lengths stay consistent. One way to attach the
pendulum is to tape the loose end to the end of a table. When the string length needs to be changed the string
simply needs to be taped at the new length. Additional weight can be added by placing additional washers onto
the pendulum by slipping the pendulum string through the hole of the washer and letting it rest on top of the
existing washer.
To obtain the data for the experiment the students will count the number of full swings the pendulum makes in
30 seconds. To find the period of one swing the total number of swings needs to be divided by 30. Each
experiment will be run a total of three times. The average of the three runs should be computed.
It is important that when these experiments are run that the pendulum be released at the same angle. Ideally the
pendulum should be released at an angle that is less than 45 degrees. Large angles affect the period differently
than at small angles.
Once all of the trials have been completed students should analyze their data and draw conclusions based on the
data.
Idaho State University’s GK-12 Project
http://www.isu.edu/%7Esanghann/Index.html
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References:
Watson, J., Watson, N. (2003). Teachers guide teaching science with the yo-yo. Duncan YoYo. Retrieved
March, 2007 from http://www.yo-yo.com/lessonplans/yo_yo.pdf
This material was developed with support from the National Science Foundation’s Graduate Teaching Fellows in K-12 Education (GK-12) program
(DGE-0338184) and Idaho State University. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the
author(s) and do not necessarily reflect the views of the NSF.
Idaho State University’s GK-12 Project
http://www.isu.edu/%7Esanghann/Index.html
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