Download Energy

Energy - What Is Energy?
Using Prior Knowledge
Before you read, look at the section headings and visuals to
see what this section is about. Then write what you know
about energy in a graphic organizer like the one below. As
you read, write what you learn.
1.
2.
What You Know
The joule is the unit of work.
Energy has different forms.
What You Learned
Energy - What Is Energy?
Kinetic Energy
Kinetic energy increases as mass and velocity increases.
Energy
Kinetic Energy
Definition
The energy of motion
Kinetic energy
depends on…
Mass and Velocity
Calculating Kinetic
Energy
½ mass times velocity2
Increase in Mass
A similar increase in kinetic energy. Example
doubling mass doubles kinetic energy.
Increase in Velocity Increase in velocity changes kinetic energy
differently due to the exponent. Example: doubling
velocity, quadruples kinetic energy.
Energy - What Is Energy?
Exponents
An exponent tells how many times a number is used as a
factor. For example, 3 X 3 can be written as 32. You read
this number as “three squared.” An exponent of 2 indicates
that the number 3 is used as a factor two times. To find the
value of a squared number, multiply the number by itself.
32 = 3 X 3 = 9
Practice Problem
What is the value of the number 82?
64
Energy - What Is Energy?
Potential Energy
Gravitational potential energy increases as weight and height
increase.
Energy
Potential Energy
Definition
Energy that is stored and held in readiness.
Gravitational
Potential Energy
Based on Height and Weight
Elastic Potential
Energy
Energy stored in objects that are stressed or
compressed
Potential Chemical
Energy
Energy stored in chemical bonds.
Calculating
Gravitational
Potential Energy
Gravitational Potential Energy = weight times
height
Energy
Energy, Work, and Power
Energy
The ability to do work or cause change
Transfer of Energy
When an object or organism does work on another
object or organism, some of the energy is
transferred to the object or organism being acted
on.
Power
The rate at which energy is being transferred
Calculating Power
The amount of energy transferred divided by the
amount of time required for the transfer. This is
described as a unit rate. The higher the unit rate,
the more power.
Energy
End of Section:
What Is Energy?
Energy - Forms of Energy
Calculating Mechanical Energy
The kinetic energy of a 500-N
diver during a dive from a 10-m
platform was measured. These
data are shown in the graph.
Energy - Forms of Energy
Calculating Mechanical Energy
Reading Graphs:
According to the graph, how
much kinetic energy does the
diver have at 8 m?
About 1000 J
Energy - Forms of Energy
Calculating Mechanical Energy
Calculating:
Using the graph, find the
kinetic energy of the diver at 6
m. Then calculate the diver’s
potential energy at that point.
Kinetic energy = about 2000
J; potential energy = about
3000 J
Energy - Forms of Energy
Calculating Mechanical Energy
Inferring:
The mechanical energy of the
diver is the same at every
height. What is the
mechanical energy of the
diver?
About 5000 J
Energy - Forms of Energy
Building Vocabulary
After you read the section, reread the paragraphs that
contain definitions of Key Terms. Use the information you
have learned to write a definition of each Key Term in your
own words.
Key Terms:
Examples:
mechanical
nuclear
energy
energy
A type
The
form
of potential
of energyenergy
associated
calledwith
nuclear
the position
energyand
is
motion in
stored
ofthe
an object
nucleus
is of
called
an atom.
mechanical energy.
electromagnetic
thermal energy
energy
The sunlight
that you
eachenergy
day is of
a form
of
total potential
andsee
kinetic
the particles
in
electromagnetic
an object is calledenergy.
thermal energy.
electrical energy
The energy of electric charges is electrical energy.
chemical energy
Chemical energy is potential energy stored in the
chemical bonds that hold chemical compounds
together.
Energy
Mechanical Energy
Definition
Mechanical energy is a result of the potential and
kinetic energy associated with an object.
Measurement
Mechanical Energy is measured in Joules (J).
Calculating
Mechanical Energy
Add together the potential and kinetic energy of an
object.
Energy
Examples of Other Forms of Energy
Thermal Energy
Created by combustion or friction. The faster the
particles move the more thermal energy produced.
Electrical Energy
Static Electricity
Chemical Energy
Energy stored in the food you eat.
Nuclear Energy
Energy stored in the nucleus of an atom.
Energy
End of Section:
Forms of Energy
Energy - Energy Transformations and Conservation
Energy Transformations
Question
Answer
What is an energy
transformation?
An energy transformation is a
change from one form of energy
to another.
What are some examples of
transformations between
potential and kinetic energy?
Juggling and pendulums show
transformations between
potential and kinetic energy.
What is conservation of
energy?
The law of conservation of
energy states that energy
cannot be created or destroyed.
Energy - Energy Transformations and Conservation
Energy Transformations
Most forms of energy can be transformed into other forms.
Energy
Potential and Kinetic Transformation
Kinetic to Potential As you throw something in the air, the kinetic
energy decreases and the potential energy
increases until the object reaches its
maximum height.
Potential to Kinetic Once an object reaches its maximum height
after being thrown in the air and begins to fall,
potential energy decreases as kinetic energy
increases.
What is
conservation of
energy?
The law of conservation of energy states that
energy cannot be created or destroyed.
Energy - Energy Transformations and Conservation
Transformations Between
Potential and Kinetic Energy
A pendulum continuously transforms energy from kinetic to
potential energy and back.
Energy
Other Transformation
Friction causes…
•Mechanical energy to convert to thermal
energy
• Because of this no machine is 100% efficient
Einstein’s Theory
of Relativity
Explains that energy can sometimes be
created by destroying matter.
Based on
Einstein’s
Theory…
In some situations, energy alone is not
conserved. However, since matter can be
transformed to energy, scientists say matter
and energy together are always conserved.
Energy
End of Section:
Energy
Transformations
and Conservation
Energy - Energy and Fossil Fuels
Previewing Visuals
When you preview, you look ahead at the material to be
read. Preview Figure 18. Then write two questions that you
have about the diagram in a graphic organizer like the one
below. As you read, answer your questions.
Using Fossil Fuel Energy
Q. What energy transformation occurs in the sun?
A. Nuclear energy to thermal energy and electromagnetic energy
Q. What energy transformation takes place when coal is burned?
A. Chemical energy to thermal energy
Energy
Fossil Fuels
Examples:
Coal, petroleum, and natural gas are all
examples of fossil fuels.
Stored as…
Chemical Potential Energy
Originated from… The sun
Release of
Release of potential energy is a result of
potential chemical burning fossil fuels. Also know as combustion.
energy
Energy
Energy Conversions
On the Sun
During nuclear fusion, nuclear energy is
transformed into electromagnetic energy and
thermal energy.
During
Photosynthesis
Electromagnetic energy from the sun is
transformed to chemical potential energy in
the plant.
During Combustion Potential chemical energy is transformed to
thermal energy.
Use of generators
Converts mechanical energy into electrical
energy
Energy - Energy and Fossil Fuels
Use of Fossil Fuels
Fossil fuels can be burned to release the chemical energy
stored millions of years ago.
Energy
End of Section:
Energy and
Fossil Fuels