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Great Robot Race, The
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Classroom Activity
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Activity Summary
Students
will design, build, and test a rubber band-powered car.
Learning Objectives
Students will be able to:
brainstorm solutions to design challenges. build, test, and evaluate a rubber band-powered car. communicate the design approach to others. distinguish between potential and kinetic energy.
- copy of the "Off to the Rubber Band Races" student handout
(PDF or
HTML)
- copy of the "Vehicle Construction" student handout
(PDF or
HTML)
- copy of the "Performance Expectations" student handout
(PDF or
HTML)
- rubber band (1/4-inch x 3-inch) (for energy source)
- bamboo skewers, pipe cleaners, drinking straws, dowels, and/or other
material (for axles)
- CDs, plain and corrugated cardboard, milk cartons, and/or other material
(for body and wheels)
- masking tape, small nails or screws, glue, staples, and/or other material
(for assembling vehicle)
- compass (for drawing circles for wheels)
- scissors
- spring scale or appropriate balance for weighing the vehicles
- tape measure or meter stick
- several 250-gram masses or objects of equivalent mass (about 100 pennies)
Background
The
purpose of this activity is for students to experience the process of designing
and building a device to meet a set of design and performance criteria just as
the teams competing in the DARPA challenge had to. The performance criteria
have been specifically chosen to present students with sometimes competing
requirements. Just as in real life, students may find that a winning solution
to a problem must involve compromise—for example, while large wheels may
mean more distance covered than smaller wheels, they also add mass to the
vehicle.
The sample rubber band car shown in the student handout consists of two axles
mounted with four wheels. The power source is the rubber band mounted around
the axle. Winding up the wheels (in reverse so they will create a forward
motion when released) winds the rubber band and stores potential energy. When
released, the rubber band spins the axle and the wheels. How far the car
travels depends upon how much potential energy is stored in the rubber band,
how efficiently the potential energy is transferred, and how much friction the
car encounters.
Key Terms
friction:
The resistance of an object to the medium through which it is traveling,
such as air or water, or that it is in contact with, such as a solid floor.
inertia: The tendency of a body at rest to stay at rest and a body in
motion to remain in motion unless acted upon by an outside force.
kinetic energy: The energy due to the motion of an object.
potential energy: The energy an object has due to its position or
internal condition rather than its motion.
Prior to vehicle construction:
Review the design rules and performance expectations. Review each part of the model car with students. Discuss the parts of the model car that might be changed to make it
travel farther (wheels, power source, body design) Explain that a front-wheel-drive car will have the rubber band winding
around the front axle, a rear-wheel-drive car will have the rubber band around
the rear axle, and an all-wheel-drive car will make use of both axles. Discuss the materials that will be used to construct the vehicle.
Students must all use the same-sized rubber band as their energy source, and
all other materials must be made from everyday supplies, such as those listed
in the materials list. Students cannot use store-bought wheels, axles, or car
bodies. Identify a relatively smooth surface where the vehicles will be
tested.
Copy student handouts and gather and distribute the materials. Require each team to draw three views of its proposed vehicle (side, top,
and rear). This will help teams further think through their design prior to
construction. Teams should use the example drawing in their handout for
guidance in making this drawing. Have students design their vehicles. Have students build, weigh, and test their vehicles. Decide on and tell
students how much time they will have to work with their vehicles. Students can
make as many changes to their vehicles as time allows, but must change and test
only one variable at a time. Make sure to allow time for any glued parts to
dry. Students should note on their three-view drawing any design changes they
made when they built their vehicle. Use the masking tape to mark the starting line and one-meter intervals down
the course. As a class, decide on a consistent method for launching vehicles so
that students do not add energy with a forward hand motion when the vehicles
are launched. Conduct the competition. Have each team carry out three or more trials of
each of the last two performance expectations (farthest distance traveled and
farthest distance traveled with load), and average the scores for each
expectation. (If your class is large, have teams carry out two trials and
choose the best trial for the final score.) You should act as scorekeeper,
keeping each team's scores private. Following the competition, have each team present its design approach. Have
students consider the following questions:
What were the benefits of drawing your design before you built your
vehicle? What worked and what didn't work in each approach? After each of your tests did your vehicle perform as expected?
Explain. What final modifications did you make to your vehicle? Why?
Announce the top three overall winners and the top three in each category.
As a class, summarize the most successful characteristics of the overall
winning designs and the most successful characteristics of those designs that
were top in their performance expectation categories. What did the winning
vehicles have in common? If students had another chance at design, what would
they do for their next-generation vehicle? Have students support their reasoning. As an extension, have students race their vehicles on a completely different terrain, such as grass or dirt. How did the vehicles perform? What changes would students make to the vehicles based on test results? Why?
Student Handout Questions
Where does the energy to move the vehicle come from? The potential energy
stored in the rubber band, which received energy from the person who wound
it. What affects the distance the vehicle travels? Students should mention
various types of friction (air resistance, resistance in the wheel bearings,
etc.) as well as the circumference of the wheels, the strength of the rubber
band, how much the rubber band was wound, and the mass of the vehicle. Describe one type of energy transfer in this activity. Correct answers
should make it clear that the energy still exists but in other forms. Three
energy transfers that occurred were kinetic to potential energy when students
wound the rubber band, potential into kinetic energy when the car was released,
and kinetic into heat energy as friction slowed the car down. What was the most difficult part of this activity? Any reasonable answer
is acceptable here. The purpose of this question is to have students think
about what they have done.
If you were going to make improvements to your vehicle, what would they be?
Why would you make them? Many different answers are acceptable here, but
more credit should be given for clear, detailed answers that are well thought
out, well presented, and based on evidence.
Web Sites
NOVA—The Great Robot Race
www.pbs.org/nova/darpa
Learn more about 12 of the teams that raced, discover some real-world
applications for autonomous vehicles, see video extras, and view a slide show
that reveals what racing robots see.
DARPA Grand Challenge '05
www.darpa.mil/grandchallenge
Provides an explanation of the event and its importance to the U.S.
Defense Department.
Rubber Band Vehicle Competition
driscoll.brookline.mec.edu/iMovieworkshop/rubberbandvehicles.html
Presents a video clip of middle school students testing their rubber band
vehicles.
Books
Absolute Beginner's Guide to Building Robots
by Gareth Branwyn. Que
Publishing, 2003.
Relates the history of robotics and provides detailed instructions on how
to build three robots—from a simple one-motor walking machine to a
programmable robot platform.
The New Way Things Work
by David Macauley. Houghton Mifflin, 1998.
Provides detailed explanations and illustrations of how things work,
including a section on digital technologies.
Robots
by
Clive Gifford. Smart Apple Media, 2006.
Describes what a robot is and looks at various ways that robots are
used.
The "Off to the Rubber Band Races" activity aligns with the following National
Science Education Standards (see books.nap.edu/html/nses).
Grades 5-8
Science Standard B
Physical Science
Motions and forces
Science Standard E
Science and Technology
Abilities of technological design
Grades 9-12
Science Standard B
Physical Science
Motions and forces
Science Standard E
Science and Technology
Abilities of technological design
Classroom Activity Author
Charles Low is a science teacher at Malden High School in Massachusetts and
has participated in a Tufts University School of Engineering program.
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