SOTM LAB: P7R
I.
TEACHER NOTES & GUIDELINES
TITLE OF LAB
Motion of a Pendulum
DEVELOPERS OF LAB
Holly Antoni, Washingtonville High School, JD702@maristb.marist.edu
Thomas Blon, Washingtonville High School, JD707@maristb.marist.edu
James Kirby, S.S. Seward Institute, JD726@maristb.marist.edu
Adapted from lab written by: Ken Evans, Kingston High School, JD881@maristb.marist.edu
OVERVIEW OF LAB
DESCRIPTION
As a group activity, students find the period of a simple pendulum. Individual groups are
asked to explore the variables of length, mass, and amplitude of swing in order to create a
pendulum with a given period.
Length of lab: 90 minutes
CURRICULUM CONSIDERATIONS
The NYS Regents Physics Syllabus requires students to demonstrate that they can
determine the period for a pendulum of given mass and length. This lab fulfills that
requirement.
Motion of a pendulum may be studied in conjunction with any of the following topics:
Unit on Energy, topic – conservation of energy
Unit of Motion in a Plane, topic – simple harmonic motion, periodic motion
SAFETY CONSIDERATIONS
Students must be aware of the proximity of other groups.
Students must attach bob tightly to the string.
BACKGROUND INFORMATION
A. SCIENTIFIC VIEWPOINT
The square of the period of a pendulum varies directly with the length of
the pendulum. Period is independent of the mass of the bob.
Assumptions are:
15 degree or less amplitude
neglect friction due to air resistance.
string does not stretch.
mass of string is negligible
B. COMMON MISCONCEPTIONS
Period increases with mass of the bob.
Period decreases as pendulum slows down and amplitude decreases.
The bob never has a zero velocity.
OBJECTIVES
1. Determine that the period of a simple pendulum depends upon pendulum length.
2. Collect length versus period data for each trial.
3. Graph length versus period data for each trial.
EQUIPMENT/MATERIALS
PROVIDED BY SOTM
Photogate timer with memory
Pasco Motion sensor
Pasco 500 Interface
IBM Thinkpad
PROVIDED LOCALLY
String
Scissors
Masking tape
Stopwatches
Pendulum clamp
Graph paper
Demos: metronome, pendulum clock, pictures
ball etc.
2 Interface cables
set of density spheres
Mass set
Balance
Meterstick
Pole support / pendulum stand
Protractor
of foucault pendulum, wrecking
ADVANCE PREPARATION
Set up simple pendulum demonstration for pre-lab.
Set up IBM Thinkpads to take data from the motion sensor.
II. PRE-LAB
PRE-LAB EXERCISE TO ELICIT STUDENTS’ PRIOR KNOWLEDGE AND
MISCONCEPTIONS
Students are broken into groups of 3 or 4.
Distribute pre-lab questionnaire. (below)
Release a simple pendulum. Ask each group to write an answer to the following
questions:
1. What is this system?
2. What other objects exhibit this behavior?
3. Why does the object swing?
4. What forces are acting on the bob?
5. What parts of this system could you vary?
6. What can we measure in this system?
7. Where is the bob traveling the fastest?
8. Where is the velocity zero?
9. What happens when the bob is released? Is it truly falling?
10. Any other observations?
DISCUSSION OF PRECONCEPTIONS
Each group will be asked to present their responses to the questions. This will branch
into a short class discussion about the misconceptions.
III. EXPLORATION OF SCIENTIFIC PRINCIPLE
& INTRODUCTION OF EXPERIMENTAL
PROTOCOL
PROBLEM
How long will it take for a 40 cm pendulum to complete 10 full swings?
EXPERIMENT AND TECHNICAL OPERATION OF EQUIPMENT
1. The teacher should explain the following:
How is the length of pendulum measured?
What range of motion defines a period?
What is the maximum angle the bob should be released from?
What is our experimental design?
How are we going to collect data? (Place a sample data table on the board to record time.)
How are we going to analyze our data and calculate one period?
2. Distribute stopwatches to groups of students. Have students do a practice run, timing the
motion of ten swings of the pendulum.
3. Take the first trial run of data. Ask the groups to report their results. Record results on the
chalk board or overhead.
4. Do a second trial run of taking data.
5. Ask students why results were not identical. Discuss possible margin for error.
6. Using the data, calculate the average time for ten swings. Divide by ten to find the period of
the pendulum. This will lead into a demonstration using the photogate as an alternative to the
stopwatch.
7. Use simple pendulum to demonstrate operation of photogate with memory. Make sure AC
adaptor has small end plug and is plugged in. (Books or blocks of wood may be needed to
raise the photogate depending on the length of the pendulum.)
8. Optional: Use the pendulum to demonstrate how to operate the motion sensor.
IV. ELABORATION OF SCIENTIFIC PRINCIPLE:
INQUIRY-BASED STUDENT INVESTIGATION
BACKGROUND
Vocabulary:
 Mass: should be relatively small, dense. Also known as “bob”.
 The mass is suspended from a fixed support with thin thread.
 Equilibrium point: the “rest” position of a simple pendulum.
 The length (l) of the pendulum is measured from the point of support to the center of the
mass at the equilibrium point.
 Cycle: a “round trip” for the bob.
 Period: the time (in seconds) for one cycle.
 Amplitude: the maximum displacement from the equilibrium point, the limit of the bob
travels to from rest position.
PROBLEM
Using the materials available, design a lab that will demonstrate the effect of the physical
characteristics of a pendulum upon the period of the pendulum.
HYPOTHESIS OR PREDICTION
Decide what variables you will measure.
Develop a hypothesis that may be tested as you gather data. Explain your reasoning.
EXPERIMENTAL DESIGN
Guidelines:
 Design a lab to show how the physical characteristics of a pendulum effect the period
of the pendulum.
 Describe methods used to perform the experiment that will test your hypothesis.
 Methods must be clearly written so that anyone may duplicate the experiment.
 Design tables to record data.
 Plan how to organize data graphically.
 Assume: small swings of pendulum (specifically, 15 degree displacement from rest
position)
Checkpoint (Teacher checks students’ experimental design for feasibility.)
Ask students:
What variables are important in your investigation?
Give a brief overview of your procedure.
What will you be measuring?
PLAN FOR DATA COLLECTION & ANALYSIS
 Prepare a table to record data.
 Plan how you will graph your results.
Checkpoint (Teacher checks students’ plan for feasibility.)
Ask students:
Does your group have tables set to record data?
How will your group show the results graphically?
CONDUCTING THE EXPERIMENT
Conduct designed experiment after it is approved by the teacher.
Checkpoint (Teacher monitors students’ investigations in progress.)
ANALYSIS OF DATA
 Graphs must be neat and legible.
 Be sure your graph has a title and labeled axes.
 What are the units of your constants? What physical meaning might go into your
constant(s) ?
Checkpoint (Teacher checks students’ analysis.)
DISCUSSION OF RESULTS
COMPARE
How do your results support your hypothesis?
What variables have other lab groups tested?
Have other lab groups found similar results?
PERSUADE
Explain what your group discovered from the results of your experiment.
RELATE
What applications can you think of for the phenomena you have observed during this lab?
What other topics in physics are related to this lab?
V. EVALUATION
POST-LAB SURVEY OF STUDENTS’ CONCEPTIONS
Have students retake the Pre-Lab Exercise. Compare pre-lab and post-lab responses.
Have students answer the post-lab questionnaire on motion of a simple pendulum. (Hand
out to students after they have done their experiment.)
TRADITIONAL
Each student must write up the pendulum experiment their group performed. The writeup must include:
Background/theory
Hypothesis
Equipment/materials
Procedure
Data
Results
Conclusions
ALTERNATIVE
1. Using the results from your experiment, design a pendulum that had a period of 2.0
seconds.
2. Demonstrate that the pendulum has the correct period. Explain how your group
arrived at this design.
3. Observe your pendulum in motion. Explain the motion in terms of velocity of the
bob as it travels through one full swing.
Alternative Assessment Rubric:
Excellent 5 pts.
-Made pendulum with period of 2.0 seconds.
-Understands that length not mass affects period.
-Can explain relationship between position and velocity.
Good 4 pts
-Made pendulum with period of 2.0 seconds.
-Understands that length not mass affects period.
-Cannot explain relationship between position and velocity.
Fair 3 pts
-Pendulum period is close to 2.0 seconds.
-Understands that length not mass affects period.
-Cannot explain relationship between position and velocity.
Poor 2 pts
-Students made an effort but achieved none of the goals.
Unacceptable 1 pt.
-Students showed no effort and achieved none of the goals.
ELABORATION:
Use the motion sensor to show how pendulum motion can be tracked.
relationships between position, velocity, and acceleration of the bob.
Identify
Use the graphing calculator to graph your results. Manipulate your data to achieve a
straight-line graph. Find the slope and compare it to theoretical constant, g/42 .
This material is based upon work supported by the National Science Foundation under Grant No. ESI 9618936. 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 National Science Foundation.
Pre-lab Questionnaire
1. What is this?
2. What other objects exhibit this behavior?
3. Why does the object swing?
4. What forces are acting on the bob?
5. What parts of this system could you vary?
6. What can we measure in this system?
7. Where is the bob traveling the fastest?
8. Is there any point where velocity is zero?
9. What happens when the bob is released? Is it truly falling?
10. Any other observations?
Post-Lab Questionnaire:
1. What is periodic motion?
2. Describe period.
3. How does period relate to the mass of the bob?
4. What is the relationship between period and pendulum length?
5. How did your data relate to your hypothesis?
Student Copy
Motion of a Pendulum
BACKGROUND
Vocabulary:
 Mass: should be relatively small, dense. Also known as “bob”.
 The mass is suspended from a fixed support with thin thread.
 Equilibrium point: the “rest” position of a simple pendulum.
 The length (l) of the pendulum is measured from the point of support to the center of the
mass at the equilibrium point.
 Cycle: a “round trip” for the bob.
 Period: the time (in seconds) for one cycle.
 Amplitude: the maximum displacement from the equilibrium point, the limit of the bob
travels to from rest position.
PROBLEM
Using the materials available, design a lab that will demonstrate the effect of the physical
characteristics of a pendulum upon the period of the pendulum.
HYPOTHESIS OR PREDICTION
1. Decide what variables you will measure.
2. Develop a hypothesis that may be tested as you gather data. Explain your reasoning.
EXPERIMENTAL DESIGN
Guidelines:
1. Design a lab to show how the physical characteristics of a pendulum effect the period of the
pendulum.
2. Describe methods used to perform the experiment that will test your hypothesis.
3. Methods must be clearly written so that anyone may duplicate the experiment. Be sure to list
any equipment or materials that will be needed.
4. Design tables to record data.
5. Plan how to organize data graphically.
6. Assume: small swings of pendulum (specifically, 15 degree displacement from rest position)
7. Before setting up your experiment you must have your design approved by your teacher.
PLAN FOR DATA COLLECTION & ANALYSIS
1. Prepare a table to record data.
2. Plan how you will graph your results.
3. Before setting up your experiment you must have your plan approved by your teacher.
CONDUCTING THE EXPERIMENT
Set up your equipment and get started! Be sure to ASK if you have questions.
ANALYSIS OF DATA
Graphs must be neat and legible.
Be sure your graph has a title and labeled axes.
DISCUSSION OF RESULTS
COMPARE
1. How do your results support your hypothesis?
2. Have other lab groups found similar results?
PERSUADE
Explain what your group discovered from the results of your experiment.
RELATE
1. What applications can you think of for the phenomena you have observed during this
lab?
2. What other topics in physics are related to this lab?
This material is based upon work supported by the National Science Foundation under Grant No. ESI 9618936. 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 National Science Foundation.