Download 9th Grade science_Lesson 1

DSCYF EDUCATION UNIT
Total marks: _________/ 30
Learning Goals for this Lesson
Standards
Standard 3: Energy and Its Effects: Energy takes
many forms. These forms can be grouped into types
of energy that are associated with the motion of mass
(kinetic energy), and types of energy associated with
the position of mass and energy fields
Students Will Know
Students Will Be Able To

Elastic potential energy (EPE) is a form of
stored “potential” energy in a stretched or
compressed material.


The amount of stretch or compression of a
substance when a force is applied is related to
the structure of the substance. This relationship
between force and stretch or compression is
called the elastic constant. The elastic
constant is different for every elastic material.


The elastic force, the elastic constant, and the
distance that the elastic material is stretch or
compressed can be related mathematically.
This relationship is commonly stated using the
equation F = kx; where x is the distance the
elastic material is stretched or compressed, k is
the elastic constant for that particular elastic
material, and F is the elastic force.

All elastic materials have an elastic limit, which
is the point at which the material no longer will
return to its original shape and no longer
behaves like an elastic material.

The amount of EPE is influenced by the type of
elastic material and the amount of stretch or
compression of this material. It is more heavily
influenced by the amount of the material’s
stretch or compression since the relationship
between the amount of stretch/compression and
EPE is exponential. (i.e., if the stretch is
doubled, the EPE is quadrupled)

An object’s EPE can be quantified by multiplying
the constant ½ by the elastic constant and the
square of the object’s stretch/compression.
EPE = ½ k x2
Lesson Essential Question
How are elastic forces and their stretch related?



Recognize that the relationship between the Elastic
Potential Energy and the elastic stretch /
compression is not simple (i.e. if the stretch or
compression is doubled, then the EPE is
quadrupled).
Quantify the EPE of an object using mathematical
equations.
Recognize that every material has a unique property
that determines the elasticity of the material known
as the elastic constant.
Recognize that each elastic material has an elastic
limit, which is the point where the elastic material is
stretched or compressed such that it will no longer
return to its original shape.
Recognize that in most examples EPE is
transformed into KE; a good example of this is
earthquakes.
DSCYF EDUCATION UNIT
Activating Strategy:
Show the Olympic pole vault picture (Energy Across Systems Investigation 4 ppt, slide #2)
Have students discuss with collaborative partners the following questions:
1. List some examples of elastic materials and describe how you think these materials would store
elastic potential energy.
2. Do elastic materials always return to their original shape and/or position? If not, what might cause
them not to do so?
Have students share their thoughts with each other; and then share out with the class. Remind students of the
transfer and transformation of energy reviewed in earlier lessons; as well as the Law of Conservation of Energy.
Key vocabulary to preview
Elastic- force, constant, and limit
Slope, linear regression
Elastic force (f) = kx (distance)(elastic constant)
Vocabulary Strategy
Have students create T-charts in notebooks; one column for word, one column for definition. Provide the definitions
for any words the students do not know; have all students write the formula for Elastic force. Explain that it will be
used later in the investigation.
Lesson Instruction
Learning Activity 1
Partner read page 1 of Investigation 4 Elastic Energy student guide (pole
vault). Provide the focus question for the investigation: How are elastic forces
and their stretch related?
Graphic Organizer

Depending on the facility, either present as teacher demonstration or have
students work in groups of 2-4 to complete.
**Teacher should set up investigation (force probe and computer) ahead of
time.
Have groups either a.) each answer one question s (1-7), or answer all
questions.
Assessment Prompt for Learning Activity 1
Exit ticket- How are elastic forces and their stretch related?
Learning Activity 2
Investigation- Elastic forces and elastic energy- Complete investigation as
whole group demonstration, or have students complete in small groups.
Focus question- How is EPE related to the stretch or compression distance of
the elastic material?
Answer questions 1-3 (in student packet, p. 11)
Assessment Prompt for Learning Activity 2
Exit ticket- How is EPE related to the stretch or compression distance of the
elastic material?
Assignment
Sports and Elastic Potential Energy
Read through page 16 in student
DSCYF EDUCATION UNIT
Learning Activity 3
Making sense of energy- EPE and Earthquakes
Read through ages 13-14 in student packet- as whole group or through
partner reading.
Complete investigation (page 15) as teacher demonstration
Assessment Prompt for Learning Activity 3
Investigation analysis and reflection questions:
1. Does each movement of the block (the earthquake) happen
predictably? Are there any patterns that arise from the experiment?
2. A student observes the graph and states that the bungee earthquake
stored more elastic potential energy than did the rubber band
earthquake. Can the student justify his conclusion using the
information provided on the graph? Explain.
Summarizing Strategy
Investigation 4 formative assessment.
packet (whole group or partner
reading). Can show sports clips
(baseball, car races, tennis, pole
vault, etc.)
Question- What other examples can
you think of to illustrate how EPE is
used in sports? Write a paragraph
explaining your examples.
DSCYF EDUCATION UNIT
FORMATIVE ASSESSMENT
Energy Chains
1. Construct an energy chain that shows
the forms of energy as well as the
energy transfers and transformations
for a baseball during a game.
Start
the energy chain with the ball moving
towards the batter and end with the ball
being caught by the outfielder.
DSCYF EDUCATION UNIT
Grade Level : 9 Unit: Energy Across Systems
Lesson: Investigation #1
This formative item measures student’s ability to describe the flow of energy in a
physical system using an energy chain.
This item links to this Delaware Science Content Standard:
3.3.1.
Energy cannot be created nor destroyed. Energy can be transferred from one object to
another and can be transformed from one form to another, but the total amount of energy
never changes. Recognizing that energy is conserved, the processes of energy
transformation and energy transfer can be used to understand the changes that take
place in physical systems.
3.3.2.
Most of the changes that occur in the universe involve the transformation of energy from
one form to another. Almost all of these energy transformations lead to the production of
some heat energy, whether or not heat energy is the desired output of the transformation
process.
Item:
Construct an energy chain that shows the forms of energy as well as the energy transfers
and transformations for a baseball during a game. Start the energy chain with the ball
moving towards the batter and end with the ball being caught by the outfielder.
Desired Response:
The ball is moving towards the batter and is elevated above the ground (KE & GPE); the
KE of the moving bat is transferred to the moving baseball during the swing, the GPE
stays the same; as the ball moves up into the air the KE of the baseball is transformed into
GPE until it reaches its highest point in the arc; as the ball returns to the ground the GPE
is now transformed into KE; as the ball is caught by the outfielder the KE of the baseball
is transferred to the player’s mitt and eventually transformed into heat energy, the ball
still has some GPE because it is elevated above the ground.
OR
DSCYF EDUCATION UNIT
Item Rubric
Level
Response
Includes an adequate energy chain, but includes more detail than
4
(Advanced) expected in an “adequate” response. Some examples may be the
interaction of the ball and the bat as a transformation of KE (of the ball)
to EPE (of the bat) for a split second and recognizing the fact that at the
top of the arc the forward motion of the ball has not been affected so it
still has a significant amount of KE (most will assume that all of the KE
of the ball has been transformed to GPE, which would only happen if the
ball was hit straight upwards).
3
(Correct)
The student responds with an energy chain that encompasses 90% or
more of the “desired response.”
2
(Partially
Correct)
1
(Incorrect)
The student responds with an energy chain that encompasses 50% or
more of the “desired response.”
0
(Off task)
Irrelevant or no response
Portions of the energy chain are scientifically incorrect or the student
responds with an energy chain that encompasses less than 50% of the
“desired response.”
DSCYF EDUCATION UNIT
Energy Across Systems
Pre-Learning Concept Check
Statement: The farther above the ground an object, such as a book, is raised,
the greater the object’s Gravitational Potential Energy (GPE).
Several students are talking about the previous statement in class. Each has different
ideas about the statement. Circle the statement below which most closely matches your
thinking and then in the space below explain your thinking process.
A. Yes, everything has some potential energy.
B. Yes, but it only gets potential energy when it falls.
C. Yes, because gravity is stronger the higher you go up.
D. Yes, one thing that determines the GPE is the distance between the object and the
ground.
E. No, there is no force or motion happening.
F. No, it is not in contact with anything which could give it energy.
Explain your thinking. Describe the “rule” or reasoning you used to select your answer to
the task.
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________________________________________________________________
________________
DSCYF EDUCATION UNIT
CORRECT RESPONSE:
The correct response is (D). Students should link an increase in height to an increase in
GPE.
STANDARD(S) ADDRESSED:
Standard #3, Strand #1
3.1.2.
An object has kinetic energy because of its linear motion, rotational motion, or both. The kinetic
energy of an object can be determined knowing its mass and speed. The object’s geometry also
needs to be known to determine its rotational kinetic energy. An object can have potential energy
when under the influence of gravity, elastic forces or electric forces and its potential energy can be
determined from its position.
WHAT DOES RESEARCH TELL US?
Research on the topic of potential energy shows that students have a difficult time
conceptualizing “potential” energy”. They can rationalize kinetic energy because they can
see something moving; with stored energies this is not the case.
Joseph Stepans (1996) notes some additional misconceptions about energy in the text
Targeting Students’ Science Misconceptions.
1. Many students believe that energy is only associated with human beings or things that
have human attributes.
2. A person pushing {an object} has energy, but the {object] can’t have energy.
3. Stored energy is something that causes energy later. It is not energy until it has been
released.
INSTRUCTIONAL IMPLICATIONS:
Teachers should be aware of the aforementioned misconceptions and target them in
classroom instruction. Students must first confront their own misconceptions before there
is a chance for them to accept new explanations. Research suggests that if this step is not
undertaken, students will revert back to their previous beliefs after the lesson is completed.
Good classroom discussion, especially in small peer groups, can be effective in identifying
the beliefs students hold about specific concepts.
DSCYF EDUCATION UNIT
INVESTIGATION #1: GETTING TO WORK WITH ENERGY
INVESTIGATING HOW FORCES TRANSFER ENERGY
ENERGY, what do you think of when you hear the word energy? Do you picture a
speeding racecar or perhaps a spinning windmill? Maybe you imagine a street luge
participant speeding down a twisting mountain road or you think of an explosion.
We frequently read about energy in the newspaper.
In the news, ENERGY usually refers to electrical energy or
the energy stored in oil/gasoline. These are two good
examples of energy that dramatically affect our daily lives.
Are there other examples? How do we make use of this
energy? Why are these two forms so important to us?
Energy is a topic that makes its way into all of the
sciences. As you move through this year’s science class
you will learn about energy in many different forms and in
many different contexts. Energy is hard to define, so we
generally define it by providing examples of energy.
Energy can move from one place to another and it can also change forms. Keeping track
of the energy in an example can help you understand and explain the science involved.
 Why is energy so important
to us?
 What types of energy do you
encounter most often?
 How does energy get from
one place to another?
GOALS:
In this lab investigation,
you will …





Review the concepts of energy transfer and energy transformation and the basic
forms of energy (from the grade 6-8 science content standards)
Discuss the significance of the Law of Conservation of Energy.
Describe how force and distance combine mathematically to quantify the energy
transfer in a process called work.
Quantify the work done (energy transferred or transformed) in examples.
Create and explain energy chains.
DSCYF EDUCATION UNIT
INVESTIGATION OVERVIEW:
A synopsis of this lesson is as follows…
In this lesson you will begin by reviewing key energy concepts from earlier grades,
primarily middle school. These ideas will be expanded upon, arriving at the concept of
work and the Law of Conservation of Energy. Energy chains will be used as a tool to
analyze energy systems. You will be asked to create crash barriers from dominoes to
investigate how forces transfer energy from a moving car. The final task it to apply what
you’ve learned to create a crash barrier from assorted materials to stop a fast moving car in
a short distance.
CONNECTIONS
Scientific Content –
Energy can exist in different forms.
 Energy can be categorized into several forms (kinetic, potential, elastic, heat,
electrical, etc.) Since energy can not be seen, it is defined by the change that
is produced when energy is transferred and/or transformed.
 Mechanical energy is the sum of both the kinetic energy (KE) and the
Gravitational Potential Energy (GPE) of an object. KE is dependent upon the
mass and speed of the object; GPE is dependent upon the mass and the
height of the object.
 Chemical potential energy (or chemical energy) is the potential energy
stored in the bonding of the particles that make up matter.
 Heat energy is the random kinetic energy of the particles that make up a
substance.
 Electromagnetic energy is the energy transferred by electromagnetic waves
 Elastic potential energy is the energy stored in elastic materials by
compressing or stretching them beyond their normal position.
 Sound energy is the energy carried by the organized vibrations of particles
as a mechanical wave.
Energy can be transferred from one object to another.
 An energy transfer occurs when energy is passed from one object to another
object but stays in the same form.
 When one object pushes or pulls on another object often (but not always)
energy is transferred from one of the objects to the other. As a result of this
transfer, the motion of one or both of the objects will change.
 When a force transfers energy, the process is called work. The “work done”
by the force involved in the energy transfer can be quantified by multiplying
the force by the distance over which that force acted during the energy
transfer process.
 When kinetic energy is transferred to a large stationary solid this energy is
transferred to the particles that make up the object. The kinetic energy may
take the form of organized vibrations within the solid (a mechanical wave), but
will ultimately become the random vibrational kinetic energy of the particles.
This collective random kinetic energy of the particles is called heat energy.
DSCYF EDUCATION UNIT
Energy can be changed from one form to another. This process is called the
transformation of energy.
 An energy transformation occurs when energy is passed from one object to
another and it changes forms.
 In most cases, the energy of objects eventually becomes the random kinetic
energy of the particles that make up the object. We call this form of energy
heat energy.
By understanding energy transformation and energy transfer, we can begin to
understand that the energy of an object can change forms and be passed to
other objects but cannot be created nor destroyed.



Energy can not be created nor destroyed. Energy can be transferred from
one object to another and can be transformed from one form to another, but
the total amount of energy never changes. This concept is known as the Law
of Conservation of Energy and is one of the most significant laws in science.
Identifying the energy transformations and transfers that occur when an event
takes place helps us to better understand what factors influence these
changes. This understanding helps us to appreciate how objects interact and
enable us to make predictions about the outcomes of these changes.
Energy chains help to understand the Law of Conservation of Energy.
Identifying where energy comes from and where it goes builds an acceptance
that energy can change form, or be transferred from object to object, but
cannot disappear. When energy seems to go away, it really is just changing
forms and spreading out. These concepts are the foundation for the Law of
Conservation of Energy.
Scientific Process  Identifying the different forms of energy, and where it is transferred
and/or transformed during an event are important skills that lead to
a richer understanding of the flow of energy in everyday
phenomena.
 Creating energy chains requires an understanding of the flow of
energy that takes place during the changes in any physical system.
Accurate completion of an energy chain and/or diagram reflects a
student’s understanding of the flow of energy in systems.
Math/Graphing  Calculations of work will be completed. Graphical displays of
energy flow will be created and analyzed.
DSCYF EDUCATION UNIT
Section I: Reviewing Key Energy Concepts
MAKING SENSE OF ENERGY …
Energy is the most central concept in all of science. Energy is the thread that ties
the physical, life, and earth sciences together. Matter and energy make up the universe.
While matter is tangible and something that we can hold in our hands, energy is far more
abstract.
We commonly say that objects have energy, but we can’t really see this energy. We
recognize energy mainly through the effects it has on objects. We see the changes that
occur when an object or substance has energy and shares that energy with other objects.
Energy is not easily defined. So scientists study energy by looking at the effects
energy has on other things. A definition that is often used
for energy is “the ability to bring about some sort of change.”
If something has energy, then that energy can cause a
change in the object or in its surroundings. By designing
experiments to study these changes, scientists learn more about energy.
Energy comes in many forms. You may remember some of these forms from your
8th grade study of energy or from previous studies in energy. It is important for us to be
able to identify the forms of energy. It is also important to be able to describe how energy
moves from one place to another and changes forms.
In some cases, the same type of energy is simply passed along from one object to
another; this is called an energy transfer. In other cases, the energy changes forms
(converted from one form of energy to another form of energy); this process is called
energy transformation. It is common for many energy transfers and transformations to
happen together. It is often helpful, in order to understand a sequence of events, to create
a description of how the energy moved. This is generally done using words and pictures;
the result is called an energy chain.
DSCYF EDUCATION UNIT
Let’s Investigate … Energy as a “change”
Part A: Investigating GPE and KE
Question #1: Does the golf ball have energy while it is sitting on the top of
the sand? (Assume that the sand represents the ground)
1. Pick up the golf ball and hold it about 25 cm above the pan.
Question #2: What type of energy does the
golf ball have while the ball is being held at a
of 25cm above the pan?
height
Question #3: How did the golf ball get its
energy? Where did this energy
come from?
2. Release the ball and discuss the crater
produced by the golf ball.
3. Repeat the process from 50 cm, 75 cm, and 100 cm (1m). Drop each ball in a
different spot in the sand so that they can be compared in the end.
Question #4: Which trial created the most change in the sand (the largest
crater)?
4. Repeat the experiment with a hollow golf ball.
Question #5: What variable was changed in this part of the investigation?
What effect did this change have on the crater in the sand?
Question #6: Did the hollow ball and the solid ball impact the sand with the
same speed? In other words, did gravity speed them up both golf balls at the same
rate?
Question #7: What can you conclude from our investigation?
DSCYF EDUCATION UNIT
A REVIEW OF SOME COMMON FORMS OF ENERGY ….
Mechanical Energy (ME) – the combination of potential and
kinetic energies. Mechanical energy is a broad category of energy that includes the
two main forms of energy, potential and kinetic. In many cases the combination of the
two forms is an important quantity to keep track of, so the term mechanical energy
refers to the sum of these two forms.
Kinetic Energy (KE) – the energy of motion. The energy associated with
moving objects is called kinetic energy (KE), and is often
referred to as the most fundamental form of energy. The
size of the KE is determined by an object’s speed and its
mass. A moving baseball has kinetic energy. If you have
ever been hit by a pitched ball, you are aware of the energy
a moving object can have.

Give three examples of other objects that may have kinetic energy.
Gravitational Potential Energy (GPE) – the energy of position. This is
energy that an object possesses due to its position. The size
of the GPE is determined by the object’s mass and its height
above the ground. As a person climbs a ladder, increasing
his/her height above the ground, he/she increases his/her
GPE.

Give three examples of objects with gravitational
potential energy.
DSCYF EDUCATION UNIT
Heat Energy (HE) – the random kinetic energy of particles. Heat energy is
the random, and very disorganized, kinetic energy of the particles in a
substance. Thermal energy is another term often used as a synonym
for heat energy. In most cases the distinction between the exact
definitions of heat energy and thermal energy is not made.
Due to the random nature of this form of energy, it is difficult to
make heat energy a useful form of energy. For this reason it is usually
the form of energy that appears at the end of energy chains. It
happens so often that scientists refer to
heat
energy as the “graveyard of energy”. For
example, if you pound a nail into a piece of wood, the nail gets
hot due
to the energy transferred to it by the hammer and the force of
friction
with the wood.

Give three examples of objects that have thermal energy.
Chemical Potential Energy (CPE) – the energy of bonds. Chemical potential
energy, sometimes just called chemical energy, is the
energy stored in the bonds that hold the particles in a
substance together. When these bonds are formed, or are
broken, energy transfers and/or transformations take place.
In many cases, the energy stored in the bonds of substances
is transformed into other forms of energy. Food is a source
of chemical energy for our bodies, so we sometimes use
‘food energy’ in place of chemical energy in energy chains
that involve people. In most cases this chemical potential energy is later transformed into
heat energy

Give three other examples of chemical potential energy.
DSCYF EDUCATION UNIT
Electromagnetic Energy – the energy of waves. This form of energy is often
referred to as solar energy or light energy. Electromagnetic energy is the energy that is
carried by electromagnetic waves. The most common form of electromagnetic energy is
“light”. Light energy is a term that can be used to describe
the energy ranges that our human eyes are sensitive to
and it may include some forms of ‘light’ that we can not
see with our eyes, such as infrared and ultraviolet. The
sun is the most important source of electromagnetic
energy for the Earth, supplying the vast majority of our
planet’s energy. In some cases, chemical potential energy
can be transformed into electromagnetic energy. This
form of energy is very important in the scientific field of
astronomy.
Electrical energy is a subset of electromagnetic energy, characterized by moving
charges.
It is used
to run
appliance
s and
make
artificial
light.
When the
charged
particles vibrate, they transfer energy by electromagnetic waves.

Give three other examples of electromagnetic energy.
DSCYF EDUCATION UNIT
Sound Energy – the energy of vibrating particles. This form of energy is
transferred by mechanical waves. The particles that make up a substance vibrate in a
highly organized manner and transfer energy through the substance. The particles in the
substance vibrate, but do not change their location. In most cases, sound energy is
classified into three categories; infrasonic is the sound that is below our human hearing
level, sonic is the sound that our human ears are
sensitive to, and ultrasonic is the sound that is
above our human hearing level. Have you ever
made a tin can telephone? If so, you have
already experimented with sound waves and
how vibrations are involved in the energy
transfer process.
A good example of the use of sound
waves is sonar. Humans have created devices
that enable us to send out a sound wave and listen for the echo so that we can determine
how far away something is to the source. Seismic waves or “earthquake” waves also fit
into this category because they involve the transfer of energy through vibrating matter in
the form of mechanical waves. Ultrasounds in the medical field are used for a variety of
purposes. Perhaps you have seen an ultrasound image of a baby. In most energy chains,
the sound energy is transformed into heat energy (the disorganized and random KE of
particles).

Give three other examples of sound energy.
Elastic Potential Energy (EPE) – energy of deformed materials.
This form of energy comes from the stretching or compressing of elastic materials.
When an elastic material is deformed (by stretching or compressing), it exerts a force,
called the elastic force, to return to its original shape. In many cases, the elastic material
DSCYF EDUCATION UNIT
is held temporarily in this deformed position and the material has a stored amount of
energy.
Bow hunters make use of EPE to shoot their arrows. The EPE of the bow string is
converted to the KE of the arrow. Catapults and slingshots also operate in this manner.
Tennis players rely on the elastic properties of their tennis racquets and the tennis ball.
Pole vaulters depend on the stored
energy in
the bent pole to help them get over
the bar.
The science behind the design of
the pole
relies on knowledge of how
material
store EPE. Surprisingly, certain
types of
rock can have elastic properties.
They can
be stretched or compressed under
huge
forces.

Give three other
examples
of elastic potential
energy.
DSCYF EDUCATION UNIT
TWO IMPORTANT PROPERTIES OF ENERGY ARE:

Energy transfer is the passing of energy from one object to another.

Energy transformation is the changing of energy from one form of energy to
another form of energy.
DSCYF EDUCATION UNIT
MAKING SENSE OF ENERGY … the Law of Conservation of Energy
We have done the entire investigation based upon the assumption that the total
energy in the example is constant (not changing). Is this true? Can we account for all of
the energy? Scientific evidence leads us to believe that all of the energy in any example
can be accounted for; it changes forms (it is transferred and transformed) but it does not go
away. This idea is called the Law of Conservation of Energy.
Energy can not be created nor destroyed. Energy
can be transferred from one object to another and can
be transformed from one form to another, but the total
amount of energy never changes.
Most of the events in our daily lives though
tend to tell us that this law is not true. How many
times have you heard about energy being “lost” or
that a machine “wastes energy”? In most cases,
what we mean is that energy has been transformed
into a form that is not useful to us so we say that
some of the energy was “lost”. What we really mean
is that the energy was transformed into a non-useful
form of energy. Heat energy is the ending form of all
energy chains.
DSCYF EDUCATION UNIT
MAKING SENSE OF ENERGY … Creating Energy Chains
What is an energy chain?
Energy is transferred and transformed all the time. It is helpful to be able to track the
‘flow’ of energy in our everyday life. A map of what happens to the energy, where it goes,
and how it changes, is called an ENERGY CHAIN. Energy chains can be created using
words, pictures, arrows, or any combination of things that illustrate the movement of energy
in an example. A good chain should include the forms of energy and any transfers or
transformations that happen in the example. It will also be helpful to identify a starting point
and an ending point.
As you get older, the management of energy will become more important to you.
Energy management will help you decide whether you should leave your computer on, or
DSCYF EDUCATION UNIT
turn it off while you are at school. On a much larger scale, our country and the rest of the
world are struggling with the cost of energy. As oil supplies shrink worldwide, serious
questions emerge.

What will we do to replace diminishing supplies of gasoline?

How much longer will coal be available?

How affordable is solar energy?

What other energy resources can we use?
Using energy chains can help you make good decisions on how to best use energy in your
daily lives.
TASK: Work with your teacher and/or independently to create an energy chain for an
example of energy movement. It can involve moving objects, such as cars, or it can involve
things such as light energy coming from the Sun.
Display and discuss your energy chains with your classmates. Make careful observations
of the forms of energy and when energy is transferred and when energy is transformed.
DSCYF EDUCATION UNIT
Section II: Investigating How Forces Transfer Energy
Let’s Investigate … Making a Crash Barrier
In automobile collisions, a great deal of energy must be transferred from the car (and
its occupants) to other objects and transformed into other forms of energy. Major
automobile manufacturers spend millions of dollars each year testing new safety features.
Engineers will talk about “energy absorbing materials” and “crumple zones” in new car
designs. They take advantage of the fact that
materials transfer energy in different ways and
at different rates.
Your ultimate task in this activity is to
engineer a crash barrier that will stop the car
without causing the passenger (represented
by a small wooden block or domino) to be
ejected from the car. Prior to this task though,
we will need to explore and discuss discus
how the concepts of energy transfer and
energy transformation can be used to prepare
us for this activity.
In order for a moving car to stop, its kinetic energy must be transferred to another
object and/or transformed into another form of energy. When the car stops, it has no KE.
Where does the energy go? What can transfer energy to an object or away from on
object? Forces are responsible for the transfer of energy. The forces are defined as
pushes or pulls. In many cases the direction of the force is important in determining
whether the force will transfer energy to an object or away from an object. We will be
investigating this relationship between force and energy transfer in the following parts of the
investigation.
DSCYF EDUCATION UNIT
Part A – Creating a Barrier to Stop the Car in the Shortest Distance
FOCUS QUESTION: What barrier design will stop the car in the shortest
distance?
You are expected to answer this question by conducting a scientific investigation.
We know that when conducting an investigation it is important to clearly identify which
variables will be changed and which variables will not be allowed to change.
Design of the Investigation
 You will be investigating how the barrier you build affects the stopping distance. You
can change the number of blocks in the barrier and the way the blocks are arranged,
but the barrier is the only thing that should be changed from trial to trial.

If we want to make fair judgments about how effectively each barrier stops the car,
than we need to ‘control’ all the other possible variables. Only the barrier should
change. Everything else (the car, the ramp, the car’s KE, etc.) needs to remain the
same.
Preparing the Ramp for Your Investigation
 Start this investigation by building a ramp. Place a block of wood under the track on
one end so that end is elevated about two inches from the table surface (the 1½ inch
2x4 width is sufficient if laid flat on table).

Start the car from the top of the ramp each time. Allow the car to roll freely down the
ramp until the 60 cm (1/2 way mark), which is where your barrier design will begin to
stop the moving car.

You will be given 15 dominoes to build your barrier. Design, build, and test a barrier
that you think will stop the moving car in the shortest distance. You do not have to
use all of the blocks, but as in any experiment, you will need to keep careful records
DSCYF EDUCATION UNIT
of how you arranged the blocks for each trial. Record your research in your journals.
You will most likely want to record the stopping distance in a data table.
Pre-Investigation Questions …
Question #1: What form of energy is present when the car is sitting at the top of
the ramp? How do you know this?
Question #2: What will happen to the energy of the car as it moves down the
ramp? What evidence could you collect to justify your answer?
Question #3: When the car strikes the barrier what will happen to the energy of
the car? How do you know this?
Question #4: Let’s assume we release the car from rest at the top of your ramp.
What can you do to be sure that the car strikes your barrier with the same
KE in each trial? Explain.
Conduct your Investigation
Record your results carefully and be prepared to report to the class
 the design of your barrier that stopped the car in the shortest distance by
exerting the largest stopping force
 the answers to the questions asked below
Question #5: What forces are causing the car to stop?
Question #6: Why is the stopping distance shorter for some arrangements of blocks than
for other arrangements?
DSCYF EDUCATION UNIT
Part B – Creating a Barrier to Stop the Car Safely
FOCUS QUESTION: What is the shortest distance that your
barrier needs to safely stop the moving car?
Background:
Using barriers to stop a real moving car can be a challenge. Using barriers to stop a
real moving car safely is an even bigger challenge. Suppose the brakes of a car or a truck
fail while the vehicle is traveling downhill on a long stretch of highway. We know that the
GPE of the vehicle will be transformed into KE as it moves down the inclined road. Without
brakes, the vehicle will leave the road and crash, or worse yet, collide with other vehicles.
The number one challenge in cases such as this is to stop the vehicle before it can cause
any damage. But it is equally important to stop the vehicle safely. If a barrier is created to
stop the vehicle quickly (in a short distance) the stopping forces acting on the vehicle will
need to be very large. The driver and passengers of the vehicle will also be stopped in a
short distance so they too must experience large stopping forces.
If the stopping force acting on a person is too large, the force will cause injury. So
your new challenge is to stop the car in as short a distance as possible, but safely! We can
simulate whether the stopping force is too small by standing a block up in the car. If the
stopping force is too large, the impact will knock the block over. As long as the block
remains upright, the stopping force will be considered small enough to be ‘safe’.
DSCYF EDUCATION UNIT
Conduct Your Investigation
Use the blocks provided to you to construct barriers to safely bring the car to rest. Be sure
to ‘control’ all the other variables in the experiment and carefully record all of your results.
Start your investigation by determining whether or not your stopping barrier from Part A is a
“safe” barrier.
Once again, record your results carefully and be prepared to report to the class
 the design of your barrier that safely stopped the car in the shortest distance
 the answers to the questions asked below
Question #7: How did the smallest “safe” stopping distance from Part B compare to the
stopping distance in Part A?
Question #8: Can you think of other materials that would make safer barriers than the
ones you made out of blocks? Explain why you think these other materials
would make safer barriers?
DSCYF EDUCATION UNIT
MAKING SENSE OF ENERGY … Work – The Transfer of Energy by Forces
To stop a moving car, all of its kinetic energy must be transferred away from the car.
This usually involves transforming (changing) the car’s KE into another form of energy. We
learned in middle school that forces transfer energy. A push or a pull can transfer energy
to a car, increasing its KE. But a force can also transfer energy away from a moving car,
slowing it down by reducing its KE.
Scientists call this energy transfer process work. Whenever a force increases or
decreases an object’s KE, the force does work. When investigating the properties of
simple machines in middle school we learned that the work done by a force when it pushes
or pulls on an object can be easily calculated.
In simpler terms:
Work done = Force x distance
W = F·d
or
How does this knowledge help us design a crash barrier that will safely
stop a car?
When a car that is traveling down a road is brought to a stop, we can say that a
force did work to remove all of the car’s KE. This force transferred the car’s energy to
some other object.
Work done by the force = KE of the car
(Stopping Force) X (stopping distance) = KE of the car
Even without knowing the details of the stopping force, this equation helps us understand
why some ‘stops’ are more dangerous than others. Suppose there are two cars moving
down a road with the same KE. The first car is
forced to stop suddenly, in a very short distance.
DSCYF EDUCATION UNIT
The second car stops slowly, taking a large distance to stop. Will the forces that stop the
two cars be the same size? We can find the answer in the equation for ‘work done’ by a
stopping force.
For the first car, the stopping distance was small (D) so
(stopping force) x (D ) = ( KE ) the KE of car 2
For the second car, the stopping distance was large (
(stopping force) X (
D) so
D ) = ( KE ) the KE of car 1
The initial KE of the two cars is the same size, but if the two stopping distances are
different, then the stopping forces must be different in size too. But which stopping force
(Fs ) is larger? Looking at the equation for work can help us.
D ) = (Fs) x (
(Fs) x (
D
) = ( KE )
If one of the cars stopped in a very short distance by colliding with a large object, the
stopping force would be dangerously large. The real problem is that the driver and the
passengers of this car also must stop in a very short distance. That means that they too
will experience very large stopping forces. These forces can be large enough to cause
bodily injury, or worse.
DSCYF EDUCATION UNIT
Summary of Investigation …
In your journal, write a concise summary of this investigation. Be sure to
address the following questions and use your data to support your responses.
 What is the difference between an energy transfer and an energy transformation?
 How can the same amount of energy be transferred (work done) if the forces acting
on the object are different?
 Can energy ever be “lost”? What is meant by the Law of Conservation of Energy?
 How can an energy chain or an energy diagram be useful in our everyday life?
DSCYF EDUCATION UNIT
Investigating Further …
SAFER CRASH BARRIERS
An excellent application of these concepts is the “soft walls” used by major racing
facilities across the nation (Dover International Speedway being one of these). The new
SAFER (Steel And Foam Energy Reduction) barriers have revolutionized the sport of
automobile racing and made it much safer for both the drivers and the fans.
So how do SAFER barriers absorb energy? The barriers move upon impact so that
the KE of the car is transferred to a very large area of the wall (a large portion of the wall
flexes upon impact). The key idea is that no one portion of the wall receives a large
amount of the car’s KE. The KE of the flexing soft wall is then transferred to the outer
permanent wall and support structure. The materials that make up the wall are not elastic.
Imagine what the collision would be like if the wall was elastic! Still other portions of the
car’s initial KE are transformed into heat energy and sound energy.
The previous illustration is a cut-away drawing of a soft wall at a race track used by the
major forms of racing. Access the site http://www.indycar.com/tech/safer.php and view the link
to the video file discussing how the Indianapolis Motor Speedway uses this technology.