Transcript Investigation #1

Investigation #1
Getting To Work With Energy
Investigating How Forces Transfer Energy
ENERGY
What is ENERGY?
What do you think of
when you hear the word
ENERGY?
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?
ENERGY defined …
• Energy is a term that is used often, yet is very
difficult to define.
• Energy is typically defined by the CHANGE
that is caused when energy changes form or
moves form one object to another object.
• The concept of energy flow is one of the most
fundamental ideas in all of science.
Review of Energy Forms
Mechanical Energy
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. A
person climbing a ladder increases her height above the ground, she
increases her GPE.
Give three examples of objects with gravitational potential energy.
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.
Electromagnetic Energy - the energy of waves. This form of
energy is often referred to as solar energy and light energy as
well. 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, 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 appliances and
make artificial light. When the charged particles vibrate, they
transfer energy by electromagnetic waves.
Give three other examples of electromagnetic energy.
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 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.
Dropping Golf Balls ...
You will drop the golf
ball from four different
heights looking for
evidence of energy by
a change that is
produced.
Goals/Objective
To determine how the varying
heights of a golf ball affects the
golf balls’ gravitational potential
energy as well as its kinetic energy
when it is released.
Hypothesis
If a golf ball is dropped at varying
heights, then its change to the
sands surface on impact will be
directly proportional to the height
at which the ball is dropped. (A ball
dropped at a low height will
produce less of a crater than a ball
dropped at a higher height.)
Material
• A golf ball
• A gallon of sand
• An 8X11 metal pan with 2 inch
sides
Investigation Reflection:
•
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)
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 height of 25cm above the pan?
•
Question #3: How did the golf ball get its energy? Where did this
energy come from?
Release the ball and discuss the crater produced by the golf ball.
Repeat the process from 50 cm, 75 cm, and 100 cm (1m).
Discuss why the craters are larger as the height
increases; what we see is a greater CHANGE. Drop each
trial’s 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)?
Introduce a hollow practice golf ball into the investigation. Repeat
the same process as was done with the solid 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?
Energy Transfer vs. Energy Transformation
• Energy TRANSFER is the passing of
energy from one object to another
object.
• Energy TRANSFORMATION is the
changing of energy from one form of
energy to another form 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.
Energy Chains
• Energy chains are graphical
representations of the flow of
energy in a system.
• They typically contain words,
phrases, and images.
Rube Goldberg
Challenge!!
Click on Picture to see commercial
Rube Goldberg challenge
• Get in gum drop groups
• You will have 15 min to design your
own Rube Goldberg invention with the
materials that your group is given.
• Once the invention is designed I would
like you show me your design and then
drawl the design in you warm up journal
• Then I would like you to complete a
DETAILED energy chain of your
invention.
• Be creative and have fun!!
Newton's first law of motion is often stated as
An object at rest stays at rest and an object in motion stays
in motion with the same speed and in the same direction
unless acted upon by an unbalanced force.
There are two parts to this statement - one that predicts the
behavior of stationary objects and the other that predicts
the behavior of moving objects. The two parts are
summarized in the following diagram.
Forces That Transfer Energy
Making Crash Barriers
Investigating How Forces Transfer Energy
Part A: Creating a Barrier
Focus Question: What barrier design will stop the car in
the
shortest distance?
Your task is to create a stopping barrier out of dominoes that
will stop the car in the shortest distance possible.
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 and 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?
Stopping Distances:
Investigating How Forces Transfer Energy
Part B: Creating a Safe Stopping Barrier
Focus Question: What is the shortest distance that your
car
needs to safely stop the moving car?
Your task is to create a stopping barrier out of dominoes that
will stop the car safely (the domino passenger can not fall
over or out of the car) in the shortest distance possible.
Stopping Distances:
Investigation Reflection:
• 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?
WORK
The Transfer of Energy
How does the previous investigation help us to
understand how forces transfer energy?
(Fs) x (
D ) = (Fs) x (
D
) = ( KE )
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.