Chapter Introduction
Lesson 1
Types of
Energy
Lesson 2
Energy
Transformations
and Work
Lesson 3
Machines
Chapter Wrap-Up
How does energy cause
change?
What do you think?
Before you begin, decide if you agree or
disagree with each of these statements.
As you view this presentation, see if you
change your mind about any of the
statements.
Do you agree or disagree?
1. Energy is the ability to produce motion.
2. Waves transfer energy from place to
place.
3. Energy cannot be created or destroyed,
but it can be transformed.
Do you agree or disagree?
4. Work describes how much energy it
takes for a force to push or to pull an
object.
5. All machines are 100 percent efficient.
6. Simple machines do work using one
motion.
Types of Energy
• What is energy?
• What are the different forms of energy?
• How is energy used?
Types of Energy
•
•
•
•
•
•
energy
kinetic energy
electric energy
potential energy
chemical energy
nuclear energy
•
•
•
•
•
mechanical energy
thermal energy
sound energy
seismic energy
radiant energy
What is energy?
• Energy is the ability to cause a
change.
• Wind, coal, nuclear fuel, Earth’s
interior, and the Sun also are sources
of energy that can be transformed into
other forms of energy, such as
electrical energy.
What is energy? (cont.)
What is energy?
Kinetic Energy
• Kinetic energy is the energy an object
has because it is in motion.
• Anything that is in motion has kinetic
energy, including large objects that you
can see as well as small particles, such
as molecules, ions, atoms, and
electrons.
Kinetic Energy (cont.)
• Electrons move around the nucleus of an
atom, and they can move from one atom
to another.
• When electrons move, they have kinetic
energy and create an electric current.
• The energy that an electric current
carries is a form of kinetic energy called
electric energy.
When the blades of wind turbines rotate,
they turn a generator that changes the
kinetic energy of the moving blades into
electric energy.
The McGraw-Hill Companies, Inc./John Flournoy, photographer
Kinetic Energy (cont.)
• Kinetic energy depends on mass.
• If the turbine blades were smaller and
had less mass, they would have less
kinetic energy.
Kinetic Energy (cont.)
• Kinetic energy also depends on speed.
• When the wind blows harder, the blades
move faster and have more kinetic
energy.
Kinetic Energy (cont.)
electric
from Greek electrum, means
“amber”; because electricity was
first generated by rubbing pieces
of amber together
Potential Energy
• Potential energy is stored energy that
depends on the interaction of objects,
particles, or atoms.
• Gravitational potential energy is a type of
potential energy stored in an object due
to its height above Earth’s surface.
Potential Energy (cont.)
• Gravitational potential energy depends
on the mass of an object and its distance
from Earth’s surface.
• The more mass an object has and the
greater its distance from Earth, the
greater its gravitational potential energy.
Hydroelectric energy plants convert the
gravitational potential energy of water into
electric energy.
Potential Energy (cont.)
• Most electric energy in the United States
comes from fossil fuels such as
petroleum, natural gas, and coal.
• The atoms that make up these fossil
fuels are joined by chemical bonds.
• Chemical energy is energy that is
stored in and released from the bonds
between atoms.
When fossil fuels burn, the chemical bonds
between the atoms that make up the fossil
fuel break apart. When this happens,
chemical energy transforms to thermal
energy.
This energy is used to heat water and form
steam. The steam is used to turn a turbine,
which is connected to a generator that
generates electric energy.
Potential Energy (cont.)
• A drawback of fossil fuels is that they
introduce harmful waste products, such
as sulfur dioxide and carbon dioxide, into
the environment.
• Scientists are searching for replacement
fuels that do not harm the environment.
Potential Energy (cont.)
• Chemical energy also is stored in the
foods you eat.
• Your body converts the energy stored in
chemical bonds in food into the kinetic
energy of your moving muscles and into
the electric energy that sends signals
through your nerves to your brain.
Potential Energy (cont.)
• The majority of energy on Earth comes
from the Sun.
• Nuclear fusion, a process found in the
Sun, joins the nuclei of atoms and
releases large amounts of energy.
Nuclear energy plants break apart the
nuclei of certain atoms using a process
called nuclear fission.
Nuclear fission produces a large amount of
energy from just a small amount of fuel.
Potential Energy (cont.)
• Both nuclear fusion and nuclear fission
release nuclear energy—energy stored
in and released from the nucleus of an
atom.
• Nuclear fission produces radioactive
waste that is hazardous and difficult to
dispose of safely.
Kinetic and Potential Energies
Combined
Objects such as wind turbine blades and
particles, such as molecules, ions, atoms,
and electrons, often have kinetic and
potential energies.
Kinetic and Potential Energies
Combined (cont.)
• The sum of potential energy and kinetic
energy in a system of objects is
mechanical energy.
• Mechanical energy is the energy an
object has because of a combination
of the following:
•
the movement of its parts (kinetic energy)
•
the position of its parts (potential energy)
Kinetic and Potential Energies
Combined (cont.)
• Thermal energy is the sum of the kinetic
energy and potential energy of the
particles that make up an object.
• Individual particles vibrate
back and forth in place, giving
them kinetic energy.
• The particles also have potential energy
because of the distance between
particles and the charge of the particles.
Kinetic and Potential Energies
Combined (cont.)
• The particles in Earth’s interior contain
great amounts of thermal energy.
• This energy is called geothermal energy.
Geothermal energy plants turn water into
steam, which turns turbines in electric
generators that covert the geothermal
energy to electric energy.
Energy from Waves
• Waves are disturbances that carry
energy from one place to another.
• Sound energy is energy
carried by sound waves.
• Some animals, such as
bats, emit sound waves
to find prey
CORBIS
Energy from Waves (cont.)
• The kinetic energy of tectonic plate
movement is carried through the
ground by seismic waves.
• Seismic energy is the energy
transferred by waves moving through
the ground.
Seismic energy can destroy buildings and
roads.
Dr. Roger Hutchinson/NOAA
Energy from Waves (cont.)
What are the different forms
of energy?
Energy from Waves (cont.)
• Electromagnetic waves are
electric and magnetic waves
that move perpendicular to
each other.
• Some electromagnetic
waves can travel through
solids, liquids, gases, and
vacuums.
Energy from Waves (cont.)
vacuum
Science Use a space that
contains no matter
Common Use to clean with a
vacuum cleaner or sweeper
Energy from Waves (cont.)
• The energy carried by electromagnetic
waves is radiant energy.
• The Sun’s energy is transmitted to Earth
by electromagnetic waves.
Radio waves, light waves, and microwaves
are all electromagnetic waves.
Energy from Waves (cont.)
How is radiant energy used?
• There are different forms of energy,
including solar energy.
• Wind turbines have different kinds of
energy including kinetic, mechanical,
potential, and thermal.
• Nuclear fuel pellets contain potential
energy that is stored in the nuclei of
atoms.
The McGraw-Hill Companies, Inc./John Flournoy, photographer
Which energy type is stored in
and released from the bonds
between atoms?
A. chemical
B. electrical
C. kinetic
D. potential
Which term refers to thermal
energy that originates from
particles in the Earth’s interior?
A. geothermal energy
B. nuclear fission
C. nuclear fusion
D. seismic energy
Which energy type is carried by
electromagnetic waves?
A. mechanical
B. radiant
C. seismic
D. thermal
Do you agree or disagree?
1. Energy is the ability to produce motion.
2. Waves transfer energy from place to
place.
Energy Transformations
and Work
• What is the law of conservation of
energy?
• In what ways can energy be
transformed?
• How are energy and work related?
Energy Transformations
and Work
• energy transformation
• law of conservation of energy
• work
Energy Transformations
• Energy transformation is the
conversion of one form of energy to
another.
• When energy is transferred, the form of
energy does not have to change.
Energy Conservation
• The law of conservation of energy
says that energy can be transformed
from one form to another, but it cannot
be created or destroyed.
• Even though energy can change forms,
the total amount of energy in the
universe does not change. It just
changes form.
Energy Conservation (cont.)
What is the law of conservation
of energy?
When you ride a roller coaster, your
gravitational potential energy is transformed
to kinetic energy and back to gravitational
potential energy.
Energy Conservation (cont.)
• When a plant carries
on photosynthesis, it
transforms radiant
energy from the Sun
into chemical energy.
• The chemical energy is
stored in the bonds of
the plant’s molecules.
Energy Conservation (cont.)
• When electric energy plants burn fossil
fuels, they transform the chemical
energy from the molecules that were
made by plants that lived millions of
years ago.
• That chemical energy is transformed to
the electric energy that you use in your
home and school.
Energy Conservation (cont.)
Identify three energy
transformations that occur
to make electric energy.
Energy and Work
• Work is the transfer of energy that
occurs when a force makes an object
move in the direction of the force while
the force acts on the object.
• Forces are pushes or pulls.
The student does work on the drums when
he lifts them. Once the drums are in place,
no work is being done.
Energy and Work (cont.)
If you do work on an object,
how will its energy change?
Energy and Work (cont.)
• To do work on an object, an object must
move in the direction of the force.
• Work is done only while the force is
moving the object.
Energy and Work (cont.)
work
from Greek ergon, means “activity”
Energy and Work (cont.)
• Work also depends on the distance an
object moves during the time the force is
applied.
• The equation for work is shown below.
Energy and Work (cont.)
• Force is the force applied to the object.
Distance is the distance the object
moves in the direction of the force while
the force is acting on it.
• The force in the equation is in newtons,
and distance is in meters.
• The product of newtons and meters is
newton-meter.
• A newton-meter is a joule.
Energy and Work (cont.)
Energy and Heat
• Friction is a force between two surfaces
in contact with each other.
• The direction of friction is in the opposite
direction of the motion.
• In every energy transformation and every
energy transfer, some energy is
transformed into thermal energy.
Energy and Heat (cont.)
• This thermal energy is transferred to the
surroundings.
• Thermal energy moving from a region of
higher temperature to a region of lower
temperature is called heat.
• Scientists sometimes call this heat waste
energy because it is not easily used to
do useful work.
• Energy is always conserved.
• Energy can be transformed into
different kinds of energy.
• Work and energy are
related.
Which energy type is radiant
energy from the Sun transformed
into during photosynthesis?
A. chemical
B. kinetic
C. mechanical
D. thermal
Which term refers to the
conversion of one form of
energy to another?
A. energy transfer
B. energy transformation
C. law of conservation of energy
D. work
In every energy transformation,
some energy is transformed into
what type of energy??
A. thermal
B. radiant
C. kinetic
D. chemical
Do you agree or disagree?
3. Energy cannot be created or
destroyed, but it can be transformed.
4. Work describes how much energy it
takes for a force to push or to pull an
object.
Machines
• What are simple machines?
• In what ways can machines make
work easier?
Machines
• simple machine
• wheel and axle
• inclined plane
• pulley
• screw
• complex machine
• wedge
• efficiency
• lever
Machines Transfer Mechanical
Energy
• Many machines transfer mechanical
energy from one object to another.
• Simple machines are machines that do
work using one movement.
Machines Transfer Mechanical
Energy (cont.)
• Simple machines do not change the
amount of work required to do a task;
they only change the way work is done.
• A simple machine can be an inclined
plane, a screw, a wedge, a lever, a
pulley, or a wheel and axle.
• An inclined plane
is a flat, sloped
surface.
• A screw is an
inclined plane
wrapped around
a cylinder.
The McGraw-Hill Companies, Inc./Jacques Cornell photographer
• A wedge is an inclined
plane that moves.
• A lever is a simple
machine that pivots
around a fixed point.
• A wheel and axle is a
simple machine that is a
shaft attached to a wheel
of a larger diameter so that
both rotate together.
Dynamic Graphics/Jupiterimages
• A pulley is a grooved
wheel with a rope or cable
wrapped around it.
Machines Transfer Mechanical
Energy (cont.)
What are examples of simple
machines?
Machines Transfer Mechanical
Energy (cont.)
• Two or more simple machines working
together are a complex machine.
• Complex machines use more than one
motion to accomplish tasks.
A bicycle is an example of a complex
machine.
Brand X Pictures
Machines and Work
• The work you do on a machine is called
the input work.
• The work the machine does on an object
is the output work.
• Machines make work easier by changing
the distance the object moves or the
force required to do work on an object.
Machines and Work (cont.)
• When the input distance of a machine is
larger than the output distance, the
output force is larger than the input force.
• Machines also can change the direction
of a force.
The window washer’s pulley system
makes the work of lifting easier.
Machines and Work (cont.)
How can machines make
work easier?
Efficiency
Efficiency is the ratio of output work to
input work.
Efficiency (cont.)
• Input and output work are measured in
joules.
• Efficiency is expressed as a percentage
by multiplying the ratio by 100%.
Efficiency (cont.)
• The efficiency of a machine is never
100%—some work is always
transformed into wasted thermal energy
because of friction.
• Lubricating the moving parts of a
machine reduces the friction between the
moving parts so that less input work is
transformed to waste energy.
Efficiency (cont.)
efficiency
from Latin efficere, means “work
out, accomplish”
Newton’s Laws and Simple
Machines
Newton’s third law
says that if one object
applies a force on a
second object, the
second object applies
an equal and opposite
force on the first
object.
Newton’s Laws and Simple
Machines (cont.)
According to Newton’s
first law, the motion of
an object changes
when the forces that
act on the object are
unbalanced.
Newton’s Laws and Simple
Machines (cont.)
According to Newton’s
second law of motion,
the change in motion
of an object is in the
same direction as the
total, or net.
• A bottle opener is a simple machine.
• There are six types of simple
machines, and a ramp is one
example.
• A bicycle is an example of a complex
machine that is made up of different
simple machines.
Which type of machine does work
using one movement?
A. complex
B. efficient
C. mechanical
D. simple
Which term describes a grooved
wheel with a rope or cable
wrapped around it?
A. complex machine
B. inclined plane
C. pulley
D. wedge
What does lubricating the moving
parts of a machine reduce?
A. efficiency
B. force
C. friction
D. work
Do you agree or disagree?
5. All machines are 100 percent efficient.
6. Simple machines do work using one
motion.
Key Concept Summary
Interactive Concept Map
Chapter Review
Standardized Test Practice
Energy causes change
by affecting the
movement and
position of objects.
Energy can be
transformed from one
form to another and
transferred from object
to object.
Lesson 1: Types of Energy
• Energy is the ability to cause change.
• Kinetic energy is the energy of objects in motion,
including electric energy. The forms of potential
energy include gravitational potential energy,
chemical energy, and nuclear energy. Thermal
energy and mechanical energy are forms of energy
involving both kinetic and potential energies. Sound
energy, seismic energy, and radiant energy are all
transferred by waves.
• Energy is used to move cars, heat homes, produce
light, move muscles, catch prey, and cook food
among many other examples.
Lesson 2: Energy Transformations
and Work
• The law of conservation of energy states that energy
can be transformed from one form to another, but it
can never be created or destroyed.
• Energy can be transformed from one form to
another in a variety of ways.
• Doing work on an object transfers energy to the
object.
Lesson 3: Machines
• Simple machines do work using one movement.
• Machines make work easier by changing the size of
the force required, the distance over which the
object moves, or the direction of the input and
output forces.
Which describes stored energy
that depends on the interaction of
objects, particles, or atoms?
A. chemical
B. kinetic
C. nuclear
D. potential
Where does the majority of
energy on Earth come from?
A. fossil fuels
B. the Sun
C. water
D. wind
Which describes how much
energy it takes for a force to push
or to pull an object?
A. energy transformation
B. friction
C. law of conservation of energy
D. work
Which term refers to two or more
simple machines working
together?
A. complex machine
B. inclined plane
C. pulley
D. wheel and axle
Which is an inclined plane that
wraps around a cylinder?
A. lever
B. pulley
C. screw
D. wedge
Which refers to the energy an
object has because it is in
motion?
A. gravitational
B. kinetic
C. mechanical
D. potential
Which describes energy stored in
and released from the nucleus of
an atom?
A. chemical
B. mechanical
C. nuclear
D. sound
Which is NOT true about what
machines are used to do?
A. They make it easier to do work.
B. They change the direction of a force.
C. They increase the amount of work
done on an object.
D. They reduce the force needed to do
the work.
Which term describes the ratio of
output work to input work?
A. work
B. simple machine
C. efficiency
D. complex machine
Which is an inclined plane that
moves?
A. lever
B. pulley
C. wedge
D. wheel and axle