Lesson Plan on
Surface Friction and Wear Characteristics of Common Materials1
ORLANDO M. PATRICIO2
E3 Teacher Summer Research Program
Texas A & M University, College Station3
Subject: Physical Science and Physics
Objectives: In this lesson, the students should be able to:
1. describe an object as it moves/slides across to different surfaces;
2. compare the length of time for the rubbing surfaces to show wear out
features and qualitatively describe the amount of wear of two rubbed
surfaces;
3. design an experiment to quantitatively measure the force of friction.
4. determine the factors affecting the amount of friction between two
rubbing surfaces and investigate the effect of lubricants on rubbing
surfaces;
5. calculate the amount of friction of two surfaces rubbing together using
different surface type, and weight or pressure;
6. explain how friction helps and hinders everything we do in everyday
life.
7. research on the practical and scientific applications of friction.
TEKS Objectives: The student is expected to:
4.C demonstrate the effects of forces on the motion of objects;
4.D develop and interpret a free-body diagram for force analysis; and
6.A identify the influence of mass or compressive force on friction.
National Science Standards:
Science as Inquiry 2a and 2b (9-12 Targets)
http://www.nasaexplores.com/standards/standards-s2.php
Physical Science 3d, 3e, and 3f (9-12 Targets)
http://www.nasaexplores.com/standards/standards-s3.php
_______________
1
A lesson plan relating the research on tribology and wear characteristics of chicken joints.
2
Teaches AP and Pre-AP Physics at the United HS Engineering and Technology Magnet in Laredo, Texas,
78041.
3
This lesson plan was developed during the 2005 E3 Teacher Summer Research Program in Texas A & M
University, College Station with the supervision and invaluable suggestions/comments of Dr. Hong (Helen)
Liang (mentor), her graduate students, and Dr. Sudeep Ingole at the Department of Mechanical
Engineering.
Lesson 1. Defining Friction and Wear-Out Time/Features
Materials: [Prepare materials ahead of time.] For each team activity:

Small round party balloon or toy car with rubber tire

Piece of wood with sandpaper one side

Carpet squares

Tile floor or wax paper

Stopwatch
Procedure:
1. Rub a small round party balloon or toy car on carpet squares for two
minutes or until wear-out features are observable.
http://www.californiaclassix.com/archive/61_MGA-V8.html
2. Record your observations and the length of time in rubbing.
3. Slide sandpaper (which is attached to a piece of wood) on carpet squares
for two minutes or until wear-out features are evident.
http://www.jwwoodcraft.com/quality.php
4. Make observations and record.
5. Repeat steps 1 through 4 using tile floor or wax paper as the other contact
surface.
6. Record your observations.
7. Determine the products of two rubbing surfaces or effects when two
surfaces come in contact.
8. Define friction.
9. Compare the length of time for the rubbing surfaces to show wear-out
features.
10. Qualitatively describe the amount of wear of two rubbed surfaces.
Homework:
The students are required to design an experiment using indigenous or
household available materials to quantitatively measure the force of friction
between two objects rub together or slide over one another.
Interpret the following illustrations and get ideas on how to design your
own experiment. When designing your own experiment be sure to follow the
scientific method of solving problems. Discuss in class your own experiment the
following meeting.
Lesson 2: Factors Affecting Friction
Materials for the teacher demonstration [Prepare materials ahead of time]:
 Miniature toy parachutist
 Sound tube
 Stack of coins
 Stack of books
 Rolling cart or any item on rollers
For each team in the lab activity [Prepare materials ahead of time]:















Four pins
Styrofoam meat tray
Masking tape
Flexible straw
Scissors
Drawing compass
Marker pens or colored markers/pens
Small round party balloon
Ruler
One stopwatch
10-meter tape measure or other measuring markers for track
Set of slotted weights, large washers, quarters, or any item that can add
weight
Oil or any lubricant
Tracks: Aluminum foil; Sandpaper; Carpet squares if floor is tiled; and Tile
floor or wax paper if floor is carpeted
Student Sheets (one set per group)
Day one:
1. Read the NASAexplores article, "Slippery When Wet!" with your students
(http://www.nasaexplores.com/show2_articlea.php?id=01-053) and then
discuss what friction is and why it is important to automobile safety using
information above and any other sources available.
2. Throw a toy parachutist in the air. Ask students how this relates to friction.
Spin a sound tube, and ask the same question. (Both items are examples
of fluid friction.) Next, push a stack of books across the floor, a stack of
coins across a desk, and ask how they relate to friction. (Both are
examples of sliding friction) Finally, use an item that rolls, and ask the
same question. Explain that this is an example of rolling friction, which is
what they will be testing in this experiment.
3. Hand out Student Sheets for each group. [Have your students in groups of
four.]
4. Distribute the materials and constructions tools to each team. Students
should plan the arrangement of parts on the tray before cutting them out.
5. Remind students to follow directions. If time allows, they can name and
decorate their rocket cars and conduct team races.
6. Teams can test cars for the next day's experiment.
Day Two:
1. Lay out the four (4) tracks on the floor approximately 10 meters long each.
Several metric tape measures or meter sticks joined together can be
placed on the floor for determining how far the cars travel. The students
should measure in 10-centimeter intervals.
2. Students will be looking at how a surface can affect car speed. In order to
gauge the results of this activity accurately, they will need to try to inflate
the balloon with the same amount of air before releasing the car each
time. Tie a loop of string around the inflated balloon before releasing the
car to measure the size of the balloon thus insuring the balloon inflates
with the same amount of air. Inflate the balloon inside the string loop each
time. Put a cap at the free-end of the straw to prevent air from coming out
the balloon before you let it go.
3. Remind students to make predictions of what they think is going to
happen, and record them on the "Rocket Car Data Sheet" before they
begin to race their cars each time.
4. Teams will race their rocket cars on each track (aluminum foil, sandpaper,
carpet squares, and tile floor) three times. One team member should blow
up the balloon, another member uses a stopwatch to time the car, another
measures the distance traveled, and one needs to record results on the
"Rocket Car Data Sheet."
5. Repeat steps 3 – 4 until all four track set-ups are done.
6. Teams will race cars on each track (aluminum foil, sandpaper, carpet
squares, and tile floor) again, this time adding some type of weights (See
materials list for suggestions). Make predictions, and record information
like before. (Repeat steps 2 - 5 above.)
7. Teams will graph the average speed results on the Student Sheet, "Rocket
Car Average Speed Graph."
8. Teams will put a lubrication fluid (i.e. oil) on the rim of the four wheels of
the rocket car and make a test run to each of the four track set-ups and
determine their speeds.
Student Sheet:
Procedure
1. Lay out your pattern on a Styrofoam tray. You need one rectangle, four
wheels, and four hubcaps. Use a compass to draw the wheels or cutout the
wheels and hubcaps patterns and trace them on the Styrofoam tray.
2. Blow up the balloon, and let the air out. This will stretch the balloon and make
it easier to blow up for the other trials. Tape the balloon to the short end of a
flexible straw, and then tape the straw to the rectangle. For the test trial,
inflate the balloon, and tie a loop of string around the inflated balloon before
releasing the car. Inflate the balloon inside the string loop each time you test
the car to help insure the balloon inflates the same amount each time.
3. Push pins through the hubcaps into the wheels and then into the edges of the
rectangle.
4. Blow up the balloon through the straw. Squeeze the end of the straw or put a
cap at the free-end of the straw to prevent air from coming out the balloon
before letting the car go. Place the car on the floor, and let it go.
5. Record data for three different trials for each track on your data sheets.
6. Add weight to your cars, secure with tape, and repeat the three trials, again
record data for each track. Put a lubrication fluid (i.e. oil) on the rim of the four
wheels of the rocket car and make a test run to each of the four track set-ups
and determine/record their speeds.
Rocket Car Data Sheet:
Trial/
Average
Type of
Track
Aluminum
Foil
1
Weight
Without
With
Without
With
2
3
Average
Sandpaper
1
2
3
Without
With
Without
With
Without
With
Without
With
Without
With
Average
Without
With
Carpet
Squares
1
Without
With
2
3
Average
Tile Floor
1
2
3
Average
Without
With
Without
With
Without
With
Without
With
Without
With
Without
With
Without
With
Prediction
Speed
Distance Time
Speed
Speed=Distance/Time
(cm)
(sec)
(cm/sec)
(cm/sec)
Rocket Car Wheels and Hubcap Patterns:
Rocket Car Average Speed Graph:
1. Label the vertical axis (y) in cm/sec for average speed. Make a scale of 5cm/sec intervals then up at the far left-hand portion of the graph. Start writing
the scale from the first row and label as 0 then the second row as 5, 10, and
so on.
2. Draw a heavy line tracing the fifth column to divide the graph into two. On the
horizontal axis (x), label the first four columns as rocket car average speed
without weight and the second four columns as rocket car with weight. Label
the first four columns as aluminum foil, sandpaper, carpet squares, and tile
floor, respectively. Do the same thing in the second four columns.
3. Plot the points on grid and compare the speed of the rocket cars in different
surface types and weights.
4. Discuss the effects of lubricants or fluid lubrication on rubbing surfaces.
Discussion/Wrap-up:


Discuss each team's findings and observations. Focus students' attention to
the relationship between the surface type and the amount of friction there is
between the car and surface, as demonstrated by the ability of the car to
move across each surface.
Explain that friction plays many roles in our everyday lives. Sometimes we
try to increase friction, while other times we try to decrease the amount of
friction depending on the circumstance.
Lesson 3: Coefficient of Friction
Discuss in class the relationship between force of friction on a surface (F f)
and the force applied perpendicular to the direction of friction (FN ). Explain how
the direct proportions (Ff
FN) can be expressed as linear functions with the
proportionality coefficient ( ); Ff = FN .
Have the students in groups of four and let them do the following activity:
Materials
(Suggested material list—all items may or may not be used. Students may wish to
use additional materials depending on their procedure design)
 Small rectangular object
 Wooden board
 String
 Masking tape
 Protractor
 Meter stick
 Spring scales
 Triple-beam balances
 Pulley
 Balance
 Weights
Procedure
1. Formulate a hypothesis about the angles at which an object will begin to
slide, the object slides at constant speed on an incline plane, and the relative
magnitudes of the coefficients of static friction and sliding friction.
2. Write a procedure using the suggested materials to measure the force of
sliding friction, which is the force needed to pull an object along a board at
constant speed when the board is horizontal; the angle at which an object at
rest begins to slide down an inclined plane; and the angle at which the same
object, already in motion, slides at a constant speed down an inclined plane.
3. Decide what data to collect and how to analyze it. Put your collected data in
an organized format.
4. Have your teacher approve your procedure before you begin the experiment.
Questions
1. Calculate the coefficient of sliding friction, using only the data on weight and
the average force of sliding friction. Then, calculate it using the angle of tilt
and the equation involving the tangent of θ. Are the coefficients equal? Why
or why not?
2. Calculate the coefficient of static friction. How does this coefficient compare to
the coefficient of kinetic friction that you found?
3. Based on your experiment, describe the factors that influence the force of
friction.
4. Does the shape of the object affect friction?
5. Compare static friction, rolling friction, and sliding friction.
6. Why do some materials increase friction and some materials reduce friction?
7. How is friction affected by surface area?
8. What effect does a lubricant have on the coefficient of friction?
Lesson 4: Advantages and Disadvantages of Friction
1. Tell your students to be with a partner.
2. Divide the class into two.
3. Have the first group research on graphics showing the advantages and
disadvantages of friction related to everyday life. They will prepare a
PowerPoint Presentation of their research and discuss them in class.
4. Have the second group research on the applications of friction in
science and engineering. They will also present their output in class.
5. Discuss the rubric in grading the students’ PowerPoint Presentation.
(You may agree on what is important. Hence, you will come up with the
rubric incorporating the student’s suggestions.)
References:
http://www.nasaexplores.com/show_58_teacher_st.php?id=030109142027
http://www.michigan.gov/scope/0,1607,7-155-13481_13487_13490-45472--,00.html
http://www.michigan.gov/scope/0,1607,7-155-10702-45460--,00.html
http://www.handsonlinelearning.com/July%20HSC.pdf#search='Lesson%20plan%20on
%20friction'
http://www.bbc.co.uk/schools/scienceclips/teachersresources/ages8_9/tr_friction_offlp.sh
tml
http://school.discovery.com/lessonplans/programs/frictioninourlives/
http://www.utm.edu/departments/ed/cece/fifth/5A2.shtml
http://www.parisisd.net/parishigh/teachers/kferguson/page2.htm
http://www.edison.edu/faculty/manacheril/phy_2048/webphy2048/Lesson17.htm