JetToy
Challenge
Teacher Guide
Troup County
School System
Training provided by
through generous funding from
JetToy Challenge Teacher Guide
What Is a JetToy?
The JetToy is a balloon-powered vehicle involving a simple rolling
chassis (vehicle body) and a balloon motor. The motor consists of a
balloon with a piece of tubing that serves as a nozzle. To prepare the
JetToy for operation, the balloon is inflated through the nozzle, and the
nozzle is sealed by covering the opening with a finger. Then the JetToy
is placed on the floor and the nozzle seal is released. The JetToy rolls
forward as air is expelled through the nozzle.
The JetToy is a simple and fun toy, easily constructed from common
materials. It can be made to look and perform in different ways to create
a variety of moving toys that represent vehicles, animals, or whimsical machines.
JetToy Design Challenge Materials
The SAE offers a JetToy Materials Kit that
contains items for a classroom of 27
students. The JetToy Materials Kit consists
of the following items:
25 JetToy Chassis Pattern Sheets
50 push-up sticks
50 push-up platforms
50 drinking straws
100 9-inch balloons
3 balloon pumps
12 5/16-inch inner-diameter clear vinyl tubing, 10 cm long
12 3/16-inch inner-diameter clear vinyl tubing, 10 cm long
12 1/2-inch inner diameter clear vinyl tubing, 10 cm long
100 #31 rubber bands
How Does the JetToy Work?
The Forward Pushing Force Objects are set in motion by unbalanced forces. Newton’s
Second Law (net force = mass X acceleration) states that if an object is acted on by an
unbalanced (net) force, it will undergo an acceleration (which is a change to the object’s
motion in the form of speeding up, slowing down, or turning). The amount of acceleration
depends on the force and the mass of the object. More massive objects require greater
forces than less massive ones to change their motion. This is why a truck has a larger engine
than a car.
To understand the concept of “balanced” vs. “unbalanced”
forces, consider the example of a car. A car sitting at rest
requires an unbalanced forward force from the engine to start
it moving. Otherwise, nothing will happen. Once it is moving,
the driver can maintain a constant speed by pushing on the
gas pedal just the right amount. In this case, although the
engine is supplying a forward force on the car, air resistance
and friction create a drag force of equal value that acts in the
opposite direction of the engine's force.
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JetToy Challenge Teacher Guide
So, although two forces act on the car (the engine’s forward force and the backward drag
force), there is no unbalanced or net force acting— so the car’s current state of motion does
not change.
Pushing harder on the gas pedal creates a little extra
forward force, causing the car to speed up (accelerate).
Removing the foot from the gas pedal removes the
engine’s forward force, leaving only the backward drag
force, and the car slows down, also changing its motion.
Turning the steering wheel supplies another force to the
car that causes it to change its direction. Speeding up and
slowing down and turning are all examples of
“acceleration,” which is a change to an object’s current state of motion.
So, technically, the gas pedal, the brake, and the steering wheel are all “accelerators.”
When the nozzle is opened, the forces inside the balloon are no longer “balanced.” The result
of this unbalanced force is a small push on the inside of the balloon that pushes until all the
air has escaped.
Friction and Air Resistance
Friction is a force that exists between all objects that slide against each other—it uses up
energy and resists the sliding motion. Friction is increased if the two objects are pushed
harder against each other. Think of sliding a box along the floor. Give it a push and it will slide
some distance until all the energy you gave it is used up. When you put weight in the box you
push the box harder against the floor, and it will slide a shorter distance. If there were no
friction between the box and the floor, the box would never slow down or stop, like a puck
gliding on an air hockey table.
There are two main sources of friction in the JetToy: friction due to the rotating wheels and
friction due to air resistance. When the vehicle is rolling, there will always be some friction
from the axle turning inside the drinking straw, and the hubs of the wheels rubbing against
the ends of the straw.
Friction can also be caused by parts of the body, or the
balloon, rubbing against the wheels, causing the JetToy to
slow down more quickly and not travel as far.
Air resistance is another type of friction. It results from the
JetToy sliding against air particles. Air resistance increases
with the frontal area of the JetToy because more air particles
have to “get out of the way.” When the balloon is fully inflated
and the JetToy begins to roll, the air resistance force is at its
greatest. The effect of air resistance can be observed if the
balloon is not centered (flops over to one side) when it is still
inflated and propelling the JetToy. If the balloon falls over to the right,
the air resistance on that side of the JetToy is greater, and it slows that side
of the JetToy down. This causes the JetToy to steer to the right until the balloon is deflated.
The effect of air resistance is less noticeable when the balloon is centered on the JetToy.
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JetToy Challenge Teacher Guide
Performance and Control of the JetToy
Here are the characteristics that students are asked to observe and record in these activities:
Distance: how far the JetToy travels (measured in a straight line, straight ahead)
Speed: slow, medium, or fast (relative speed will suffice)
Time: the duration of travel
Construction Features
Construction methods influence the performance of the JetToys in several ways. Poor
construction may increase friction or air resistance, causing the JetToy to go slower or stop
sooner. Heavy construction will have the same effect as adding weights. (See Weight section
below)
Nozzle Size
The size of the nozzle affects the performance of the JetToy in several ways: duration of
travel, travel distance, and speed. As discussed earlier, the nozzle size determines how
much pushing force the balloon creates. The forward pushing force is proportional to the area
of the nozzle opening; therefore, a larger nozzle will produce a greater pushing force.
However, more air can leave through a larger hole than a smaller one; so a balloon with a
larger nozzle will deflate sooner and will push the vehicle for a shorter time. The air escapes
from the balloon more slowly with a small nozzle, and the pushing force exists for a longer
time. A JetToy with a small nozzle accelerates more gradually, but may roll for a longer time
than a JetToy with a large nozzle. The effects of both nozzle size and weight are too
complicated for us to predict, so let’s find out by experience.
Will the JetToy travel farther with a large nozzle or a small one? The larger force produced by
a larger nozzle is better able to overcome rolling friction and accelerate the vehicle more
effectively. You will find that the medium (5/16-inch) and large (1/2-inch) nozzle both propel
the JetToy significantly farther than the small (3/16-inch) nozzle, and that the large nozzle
propels the JetToy a small amount farther than the medium one. You can imagine that if the
small nozzle produced a force smaller than the friction force, then it would not move the car
at all even though it pushed it for a very long time.
Another effect from different nozzle sizes is the speed of the vehicle. Greater force means
that a JetToy with a larger diameter nozzle will have a greater acceleration, but for a shorter
time, and will therefore reach a higher speed more quickly than a JetToy with a smaller
diameter nozzle.
Weight
Students may add weight to the JetToy by building heavy structures or attaching decorations,
or by adding weights for the JetToy to carry. Adding weight to the JetToy affects the
performance by increasing friction between sliding parts and by making it harder for the
motor’s pushing force to accelerate the vehicle. This means that any added weight will make
the JetToy go slower and roll a shorter distance.
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JetToy Challenge Teacher Guide
A JetToy with a medium or large nozzle can carry significantly more weight than a JetToy
with a small nozzle. With the small nozzle, even a small amount of added weight (a few
pennies) may make the JetToy too heavy for the balloon to move.
Note that JetToys with medium and large nozzles are affected differently by the addition of
weight. You will see that added weight shortens the travel distance of a JetToy with a
medium nozzle more than a JetToy with a large nozzle.
Balloon Inflation
The amount of energy stored in the balloon increases as the balloon is inflated more. Larger
balloons make the car go faster and/or farther. This factor is not emphasized in the activities,
but students should be able to identify it as a major factor in determining travel distance,
speed, and duration. Since the balloon inflation effect may overshadow the effects of motor
size and added weight, students will need to keep balloon inflation constant if they are testing
other variables.
To help control this variable, use the String Method. Cut a piece of string to the desired
circumference size. Hold it around the widest part of the balloon. When the ends of the string
just touch, the balloon is ready. The circumference is pi x the diameter; for an 8-inch balloon
the circumference is 25 inches. Or, students can use the 8-inch diameter circle template.
What Difficulties Might Students Have?
Following are some common construction problems and possible solutions:
1. The balloon rubs against the wheels as it deflates, causing friction, and stops the car
prematurely. If this happens, students can try to design these body features that keep the
balloon away from the wheels:
• Fenders that go up and over the wheels.
• A higher mounting platform for the nozzle so the balloon falls down instead of to the
side.
• A wider or longer car so the balloon cannot reach the wheels.
2. The inflated balloon flops to one side when the car is traveling, increasing air resistance on
one side, and causing the car to veer off to the side. If this happens, students can add one of
these structures to keep the balloon in the center of the car:
• A ring that goes around the balloon.
• Walls that keep the balloon from going side to side.
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JetToy Challenge Teacher Guide
3. The nozzle is not mounted straight and makes the car veer off to the side. If this happens,
students may do the following:
• Be careful to point the nozzle directly backward. Since the tubing tends to have a
natural bend, fasten it so the tube curves up or down, not to the side.
• Make a straight groove or V-shaped “nozzle guide” for the nozzle to rest in. Use tape
or twist-ties to hold it in place.
4. The body is not flat and the wheels are not squarely on the ground, causing the car to veer
to the side. If this happens, students should try to get all four wheels back on the ground:
• Re-tape the corners so the bottom of the body is flat.
• Add stiffeners to hold the body flat.
• Add weight over the front and/or back wheels that are not on the ground.
5. The axles are not parallel, causing the car to veer to the side. If this happens, students
should remount the straws on the bottom of the body until they are aligned and parallel to
each other.
6. The wheels rub against the side of the car, causing the car to stop prematurely. If this
happens, students should remount the straws on the bottom of the body, making sure the
straws overhang the body on each end but do not rub the hubs of the wheels.
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JetToy Challenge Teacher Guide
Activity 1: Building and Testing the JetToy Chassis
Purpose of the Design Challenge
A goal of this design challenge is for students to build a JetToy that rolls straight and
smoothly (with low friction at the axles and wheels). The JetToy has two main components: a
rolling chassis and a balloon motor, both of which might contribute to problems with rolling
straight and well.
Each design team builds a simple chassis and uses a ramp (the force of gravity) to get it
rolling. In testing their chassis, students will discover the design factors that contribute to
rolling problems: friction at the wheels and the axles, alignment of the axles, and how well
they constructed the chassis.
Explain that design teams will begin by building a JetToy chassis and will use a ramp to see
how well the chassis rolls. Make sure they understand the goal of this activity: to build a
rolling chassis that rolls straight and smoothly. Discuss with students how the quality of their
construction affects the performance of the toys, and encourage them to pay close attention
to construction techniques.
Identify some of the components:
chassis (the folded poster board that forms the
body of the vehicle)
hub (the center part of the wheel that holds the
axle)
axle (the rod that connects to the wheels)
bearing (the drinking straw that supports the
axle)
Time
2 class periods
Materials
1 JetToy Chassis Pattern (in JetToy Materials kit) per group
Building the JetToy Chassis handout
2 axles (in JetToy Materials kit)
4 wheels (in JetToy Materials kit)
1 drinking straw
scissors
masking tape
3 pieces of heavy cardboard or mounting board approximately 30 x 45 centimeters (12
x 18 inches) for test ramps
a meter stick or tape measure
3 test areas, each a 2-meter-long table or floor area
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JetToy Challenge Teacher Guide
Activator: Thinking About Balloon Power
Inflate the balloon and let it fly across the room. The balloon flies about, but is very erratic.
Ask students to think about how they might harness balloon power to make a vehicle move.
• How could you use this balloon to power a vehicle?
• What are some of the problems you might have to solve?
To demonstrate one way to harness balloon power in a controlled way, tie a string that has a
drinking straw threaded on it across your classroom. Inflate an oblong balloon and use
masking tape to attach it to the drinking straw. Let it fly across the room. Ask students for
their ideas about what makes the balloon go.
Preparation for this Activity
Build a JetToy chassis to show the class and familiarize yourself with the
activity. Use the student instructions to construct the JetToy chassis.
Prepare space for vehicle testing. Build at least 2-3 ramps for student use.
For each ramp, stack up books to a height of approximately 22 centimeters (9 inches). Tape
the narrow end of a 30-centimeter-wide x 45-centimeterlong piece of heavy cardboard or
mounting board to the top of each stack. Leave a clear, flat area about 2 meters long where
teams’ chassis can roll after they leave the ramp. Students should conduct at least three
trials on their chassis to ensure it rolls straight and a specified minimum distance. Additional
trials and modifications may be needed.
Sharing and Interpreting
Allow time for class discussion about how the teams solved the problem of making the rolling
chassis work. Here are some questions that might help start the discussion:
What was hard about putting the vehicle together?
What was hard about making it roll straight and smoothly?
What problems did you solve in getting your vehicle to roll straight and smoothly?
Introduce terms that are helpful in discussing performance and problems:
Friction at the wheels and/or axles (the force between moving parts that tends to slow
them down)
Alignment of the axles (aligned axles are parallel to each other)
Pre-assessment
Students will complete a short Pre-Assessment. The pre-assessment is not meant to assess
what students have been taught or should be expected to know, but to assess what they
understand so far about how balloon-powered vehicles work. It serves as a baseline
assessment, for comparison with the knowledge they display at the end of the challenge.
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JetToy Challenge Teacher Guide
Activity 2: Adding a Balloon Motor
Description of this Activity
Students assemble a balloon motor and add it to the chassis they built in Activity 1. The
balloon motor consists of a short piece of tubing (the nozzle) fastened inside the neck of a
balloon by a rubber band. Students then do informal experiments with the balloon-powered
vehicle and observe its behavior.
Time
1-2 class periods
Materials
Group’s JetToy Chassis
1 nine-inch round balloon (in JetToy Materials kit)
1 piece of 5/16-inch inner-diameter plastic tubing, 10 centimeters long (in JetToy
Materials kit)
1 small rubber band (in JetToy Materials kit)
JetToy Data handout
Preparation for this Activity
Build a balloon-powered JetToy to show the class and familiarize yourself with the activity.
Use the student instructions to construct the balloon-powered JetToy. Prepare space for
vehicle testing. You will need three clear, flat floor areas about 10 meters long by 3 meters
wide. If possible, use masking tape to mark off a starting line and regular increments on the
surface so students can measure distance. Mark each 25 centimeters up to 10 meters. See
diagram below.
Tip: If the floor surface has regularly spaced markers (such as floor tiles or patterned carpet),
measure those and label the intervals for student use. A 12-inch floor tile is just over 30
centimeters long.
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JetToy Challenge Teacher Guide
Presenting the Challenge
Explain that they are going to power the chassis with a balloon motor and test it. Their goal is
to have a vehicle that rolls straight and smoothly. As they test their vehicle, students may
have new problems in getting it to go straight and far. They need to be creative as they add
new features to solve these problems. Explain that design teams can use poster board and
tape to create these new features. There are several ways to mount the balloon motor on the
chassis. Help to guide students to these possible solutions.
a. Make a hole or notch in the rear wall of the chassis, insert
the end of the nozzle through it, and tape the nozzle to the
chassis. Possible problems with this method include a
decrease of strength at the rear of the chassis (from the hole
or notch) and a tendency for the vehicle to veer off to one
side if the hole is not centered.
b. Mount the motor on a vertical support. This support can
simply be a piece of poster board taped to the back chassis
wall. A hole supports the nozzle. Tape the nozzle to the
chassis as well.
c. Mount the motor on a platform. Students
can build a small platform from poster board. It should be at least
as high as the rear chassis wall. The nozzle could then be taped
to this platform.
Explain that students can repeat this modify-and-test cycle until the vehicles go straight for at
least a few meters. Inform students that the quality of their construction will affect the
performance of the vehicles; they will need to pay close attention to construction techniques.
Ask students to record their problems and solutions and note the changes in performance in
their design logs.
Identify some of the components and terms they might use in discussing performance and
problems:
Nozzle – The 10-centimeter-long piece of plastic tubing
Air Resistance – The force that acts to slow down any object moving through air. The
bigger the object, and the faster it goes, the greater the air resistance that acts on it.
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JetToy Challenge Teacher Guide
Testing the JetToys
When design teams have assembled a JetToy, discuss the testing procedure. Establish how
design teams will share the testing areas, and what design teams will be doing while they are
waiting for a testing station. The tests should not take a long time, but you may want to set a
time limit for each team at a testing station.
Students need to practice inflating the balloon to a consistent size, then sealing the nozzle
until they are ready to release it. This can be tricky since the balloon motors are attached to
the vehicles. One way is to inflate the balloon, then use two fingers to clamp the neck of the
balloon shut behind the nozzle. Then remove the nozzle from the pump and seal the nozzle
with a finger. Sealing the nozzle with a finger, instead of pinching the balloon, will make it
easier to do testing and help the chassis roll straight.
Design teams must take care to line their JetToy up behind the starting line. They should hold
the vehicle gently, and release the vehicle as soon as they take a finger off the nozzle. They
should be careful not to hold the vehicle back (release it too late) or push the vehicle. It may
take a few tries to get the timing right. Discuss how to use the measuring device (meter stick
or marked masking tape) to mark the distance the JetToy travels. Students should record
data on the Balloon-Powered JetToy Data sheet for as many tests as needed.
Facilitating Student Exploration
Explain to the students that the goal of this activity is to build a chassis that rolls straight and
smoothly under balloon power. However, it is not enough to simply create a working JetToy.
Students are expected to begin building an understanding of why the vehicle performs the
way it does and how they can change its performance by using a different nozzle, or by
modifying the body in some way. Below are observations and performance problems
students may notice:
Heavier vehicles travel shorter distances than lighter ones – unlike the roll test in the
previous activity
Air resistance slows the vehicle
A balloon inflated more will travel farther than a balloon inflated less
A balloon that has flopped to one side may cause the vehicle to spin or veer to one
side
A balloon that flips upward as the vehicle is traveling can crimp the neck of the
balloon, cutting off the airflow
Cars whose axles have been moved may no longer travel straight
A balloon rubbing against the wheels slows down the vehicle
Wheels that rub against the body of the vehicle will cause the vehicle to travel slowly
and not as far
A balloon motor whose nozzle is not directed straight back may cause the vehicle to
travel off to one side. If the nozzle is curved, it should be curving up or down, not to the
side, or the vehicle may turn
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JetToy Challenge Teacher Guide
Activity 3: Discussing First Results and Science Concepts
Description of the Activity:
Students have spent the last two class sessions working to get their vehicles rolling straight
and smoothly—first when rolling down a ramp, then when powered by a balloon. They are
developing some hypotheses about what makes the vehicles work well, and may be able to
identify a vehicle that will not roll well before they even try it out. Now they have collected data
and made lots of observations—it is time to try to make sense of the data and learn from
others with similar experiences.
Time
½ - 1 class period
Sharing and Interpreting
Call students’ attention to the progress they have made since they built their first test
vehicles.
• How well did your vehicle roll at the beginning of the ramp test?
• How well did your vehicle roll at the end of the balloon test?
Ask each design team to state the farthest distance its vehicle traveled. Write these numbers
on the board. Compare the numbers.
• Why are these distance numbers similar or different?
The distance numbers should be fairly similar because the students tested similar vehicles.
The numbers may be different because students inflated their balloon to different sizes, or
other aspects of their testing techniques were different.
Ask students to share the problems they had with their vehicles.
• What problems arose in getting the vehicle to go straight and far?
• What problems were there with the design of the chassis?
List what design teams did to solve their problems and what happened as a result. Be sure to
note what students tried that did not work as well as those that did.
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JetToy Challenge Teacher Guide
Introducing Science Concepts
Help students identify some of the phenomena they have been observing. Some basic
properties that underlie what they have been observing are accelerating forces, friction, and
inertia.
Accelerating Forces: To make an object move, there needs to be some force acting to set
the object in motion. The forces they have observed are gravity (rolling down the ramp) and
air pressure (from the balloon motor). The jet of air coming out of the balloon acts just like the
jet of gases that push a jet airplane or a rocket to supersonic speed.
Air Resistance: Another force acting on an object moving in air results from the object
having to push the air out of its way as it moves. This force acts as a pressure on the front of
the object and tends to slow it down. The force is proportional to the area of the front of the
object.
Friction: Friction is the force that acts to resist motion and use up energy—it slows down all
moving things. There are two main sources of friction in the balloon vehicle: friction due to the
rotating wheels and air resistance. Students are reducing friction when they make sure that
the sides of the wheels are not rubbing against the body of the vehicle. Friction from the
air pushed aside by the moving toy also tends to slow it down. Air resistance is greatest when
the large balloon is fully inflated. Jet airplanes avoid this resistance by flying very high where
there is little air. In outer space where there is no air, it is missing entirely.
Inertia: Inertia is the physical property that keeps an object moving after the accelerating
force is gone. After the vehicle has left the ramp, or after the balloon is completely deflated,
the vehicle will often continue to roll. This is due to the inertia of the vehicle.
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JetToy Challenge Teacher Guide
Activity 4: JetToy Nozzle Wars
Description of the Activity:
Students assemble balloon motors in three sizes and use varying weights to experiment with
the performance of the JetToy. Based on their observations of the vehicle's performance,
they will begin to get a sense of the effects of different balloon motors and added weight.
The goal of revising the JetToy is to create a vehicle that
• rolls straight and goes at least a meter with each nozzle size
• accepts the three different sizes of balloon nozzle and has a place to carry the
weights provided
• is sturdy enough to be used for formal experimentation
Time
1-2 Class periods
Materials
Group’s JetToy
Data sheet per group
3 nine-inch balloons (in JetToy Materials kit) per group
1 10-centimeter-long plastic tubing (nozzle) with 3/16-inch inner diameter (in JetToy
Materials kit) per group
1 10-centimeter-long plastic tubing (nozzle) with 5/16-inch inner diameter (in JetToy
Materials kit) per group
1 10-centimeter-long plastic tubing (nozzle) with ½-inch inner diameter (in JetToy
Materials kit) per group
3 small rubber bands (in JetToy Materials kit) per group
Weights per group
a string measuring 25 inches for each group and/or the 8-inch diameter circle template
scissors
masking tape
a meter stick or tape measure
3 testing areas, each space 10 meters long x 3 meters wide
extra balloons and rubber bands
3 balloon pumps (in JetToy Materials kit)
Preparation for this Activity
Prepare areas for vehicle testing as in Activity 2.
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JetToy Challenge Teacher Guide
Testing the JetToys
When most design teams have assembled a new JetToy, discuss the testing procedure.
Establish how design teams will share the testing areas, and what design teams will be doing
while they are waiting for a testing station. The tests should not take a long time, but you may
want to set a time limit for each team at a testing station.
Facilitating Student Exploration
As students evaluate their new vehicle’s performance, they begin to identify new problems—
perhaps things that have not come up in past activities. Remind them to record the problem
and their thoughts about how to solve it, then encourage them to try out their solutions. Let
the students continue working in this way until all or most of the vehicles are running straight
and smoothly.
Below are observation and construction issues that students may notice:
• Heavier vehicles may travel shorter distances than lighter ones.
• Nozzle size affects travel distance.
• Larger nozzles usually start off faster.
• The large nozzle exaggerates any tendency for the vehicle to turn.
• Air resistance causes the vehicle to slow down.
• Inflating the balloon more causes a vehicle to travel farther.
• The weights slide around in the vehicle if they are not taped down.
• The location of the weight makes a difference in the stability of the vehicle.
• Students may find it difficult to mount the nozzles so they point straight back. A
nozzle that is not pointing straight back may cause the vehicle to travel off to one
side. If the nozzle is curved, it should be curving up or down, not to the side, or the
vehicle may turn.
• New mounting features get in the way of the balloon or rub against the wheels.
• The new vehicle doesn't travel as far as their first vehicle did.
• They can't get the vehicle to move at all under balloon power.
Troubleshooting Problems with the JetToy
Students may encounter some of the problems listed below. Some possible solutions are
described here. Help guide student teams to develop these solutions on their own.
1. The balloon rubs against the wheels as it deflates and stops the vehicle.
Possible Solutions:
fenders that go over the wheels to
prevent the balloon from touching them
a higher mounting platform for the
nozzle so the balloon falls straight
down instead of off to the side
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JetToy Challenge Teacher Guide
2. The balloon flops from side to side when the vehicle is
traveling, causing the vehicle to veer off to the side.
Possible Solution:
making a holder out of card stock for the
balloon
3. The balloon flips upward as the vehicle is traveling, crimping the neck of the balloon and
cutting off the airflow.
Possible Solutions:
inserting the nozzle farther into the neck of the balloon
making a holder for the balloon out of card stock or straw
4. It is hard to attach the nozzle so that it points directly backward.
Possible Solution:
a nozzle guide (made of straws
or card stock)
5. The weight shifts, causing the vehicle to be unstable as it travels.
Possible Solution:
tape the weight to the vehicle
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JetToy Challenge Teacher Guide
Activity 5: JetToy Surface Wars
Description of the Activity:
Groups will select the JetToy vehicle from Activity 4 that performed the best (furthest and
straightest). Groups will test the JetToy on three different surfaces to determine which
surface allows for greater distance.
Time:
1 Class period
Materials:
Group’s JetToy from Activity 4 (including desired nozzle size)
Data sheet per group
1 nine-inch balloon (in JetToy Materials kit) per group
1 small rubber band (in JetToy Materials kit) per group
weights as needed per group
a string measuring 25 inches and/or the 8-inch diameter circle template for each
group
scissors
masking tape
a meter stick or tape measure
1 testing area on a tiled floor, measuring 10 meters long x 3 meters wide
1 testing area on a concrete side-walk, measuring 10 meters long x 3 meters wide
1 testing area on a carpeted surface, measuring 10 meters long x 3 meters wide
extra balloons and rubber bands
3 balloon pumps (in JetToy Materials kit)
Preparation for this Activity
Prepare areas for vehicle testing as described in the Materials section.
Testing the JetToys
When most design teams have assembled a new JetToy, discuss the testing procedure.
Establish how design teams will share the testing areas, and what design teams will be doing
while they are waiting for a testing station. The tests should not take a long time, but you may
want to set a time limit for each team at a testing station.
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JetToy Challenge Teacher Guide
Activity 6: Bringing It Back to Science
Description of the Activity:
Identify and discuss the science concepts of the JetToy Challenge.
Time
1 Class period
Materials:
Bringing it Back to Science handout
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JetToy Challenge Teacher Guide
Bringing it Back to Science – ANSWER KEY
Use the image below to identify the forces at work in the JetToy.
1. List the forces acting on
the front of the JetToy:
2. List the forces acting
on/in the balloon:
Air resistance – type of
friction
Air pressure
3. List the forces acting
on the surface used for
the JetToy:
Force of friction
4. List the forces acting
on the rotating wheels:
Force of friction
5. Look at the diagram to the right. What is
the accelerating force at work (other than
air pressure)? Gravity
6. When the JetToy has left the ramp, or after the balloon is completely deflated, what
force might keep the JetToy moving? Inertia
7. In general, what causes the JetToy to move? (hint: it has to do with forces)
Unbalanced Forces
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JetToy Challenge Teacher Guide
8. Explain how the extent of balloon inflation affects the performance of the JetToy.
The amount of energy stored in the balloon increases as the balloon is inflated more. Larger
balloons make the car go faster and/or farther.
9. Which figure to the right has the greatest air
resistance? Why? Figure 1 has the greatest air
resistance because friction is the greatest when
a balloon is fully inflated.
Figure 1
Figure 2
10. Explain how air resistance is a type of friction that can affect the performance of
the JetToy.
Air resistance increases with the frontal area of the JetToy because more air particles have to
“get out of the way”. When the balloon is fully inflated and the JetToy begins to roll, the air
resistance force is at its greatest. If the balloon is not centered and flops to one side while
still inflated, the air resistance on that side is greater, and it slows that side of the JetToy
down. This causes it to steer to the right until the balloon is deflated.
11. How does a larger nozzle size affect the performance of the JetToy?
A larger nozzle will produce a greater pushing force. However, more air can leave through a
larger hole than a smaller one; so a balloon with a larger nozzle will deflate sooner and will
push the vehicle for a shorter time.
12. How does a smaller nozzle size affect the performance of the JetToy?
The air escapes from the balloon more slowly with a small nozzle, and the pushing force
exists for a longer time than a JetToy with a large nozzle.
13. Will the JetToy travel farther with a large nozzle or a small one? The larger force
produced by a larger nozzle is better able to overcome rolling friction and accelerate the
vehicle more effectively.
14. How does weight affect the performance of the JetToy? Adding weight to the JetToy
affects the performance by increasing the friction between sliding part and by making it
harder for the motor’s pushing force to accelerate the vehicle. This means that any added
weight will make the JetToy go slower and roll a shorter distance.
15. Identify ways to reduce friction in the performance of the JetToy.
Make sure that the sides of the wheels are not rubbing against the body of the vehicle
Make sure that the balloon is not rubbing against the body of the vehicle
Roll the JetToy on a smooth surface
Make sure that the balloon is centered on the JetToy so that the effect of air resistance is less
noticeable
Decrease the weight of the JetToy because weight adds friction
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