Download Energy - My Haiku

Using Energy and Heat
Forms of Energy
Energy
Some breakfast cereals promise to give you enough energy
to get your day off to a great start. News reports often mention
the price of oil, which is an energy source that provides
fuel for cars and for transporting goods around the world.
Weather reporters talk about the approach of a storm system
that has a lot of energy. News anchors report on earthquakes
and tsunamis, which carry so much energy they cause great
damage. Politicians talk about the nation’s energy policy and
the need to conserve energy and to find new energy
resources.
Energy influences everything in life, including the climate,
the economy, and your body. Scientists define energy as the
ability to cause change.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Potential Energy
Think of a book balanced on the edge of a desk. The
book’s position could easily change, which means it has
potential energy. Potential energy is stored energy due to the
interaction between objects or particles. Particles include atoms,
ions, and molecules. Objects have potential energy if they
have the potential to cause change. Examples of potential
energy include objects that could fall due to gravity and
particles that could move because of electric or magnetic
forces.
C352_001_006_RE_L1_889408.indd 1
3/8/10 11:15:53 AM
Gravitational Potential Energy
Do the items stored on the shelves in your home have
potential energy? Yes. Every item—including the shelves—has
gravitational potential energy. Objects have gravitational
potential energy if they have mass and height above Earth’s
surface. The gravitational potential energy of an object
depends on two factors—the mass of an object and the
distance of the object from Earth’s surface.
Chemical Energy
Suppose you put on skates to play ice hockey. Where does
your body get the energy it needs to play? Energy in your
body comes from the foods you eat. All objects, including
food, are made of atoms that are joined by chemical bonds.
Chemical energy is the energy stored in and released from the bonds
between atoms. Your body breaks chemical bonds in foods and
converts the released energy into other forms of energy that
your body can use.
Nuclear Energy
Kinetic Energy
Are you moving your hand as you take notes? Are you
squirming in your chair as you try to find a comfortable
position? If so, you have kinetic energy—energy due to motion.
All objects that have motion have kinetic energy.
Kinetic Energy of Objects
An object’s kinetic energy is related to the mass and the
speed of the object. For example, suppose you hold a 3.6-kg
bowling ball in your hands. Because the bowling ball is not
moving, it has no speed and, therefore, no kinetic energy.
Now suppose a friend rolls a 4.5-kg bowling ball at 8.0 m/s
and another friend rolls a 5.5-kg ball at the same speed. The
ball that has a greater mass has greater kinetic energy even
though both balls are moving at the same speed.
C352_001_006_RE_L1_889408.indd 2
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
The energy stored in and released from the nucleus of an atom is
called nuclear energy. When you watch the Sun set, you are
experiencing nuclear energy. The Sun’s energy is released
through the process of nuclear fusion. During nuclear
fusion, the nuclei of atoms join together and release large
amounts of energy. Nuclear energy also is released when an
atom breaks apart. This breaking apart of an atom is called
nuclear fission. Nuclear fission is used in nuclear power
plants to generate, or make, electricity. Nuclear fusion and
nuclear fission are examples of nuclear energy.
3/8/10 11:15:56 AM
Electric Energy
Even objects you cannot see have kinetic energy. Recall
that all materials are made of atoms. In an atom, electrons
move around a nucleus. Sometimes electrons move from one
atom to another. Because electrons are moving, they have
kinetic energy. When electrons move, they create an electric
current. The energy in an electric current is electric energy. For
example, in a simple circuit electrons move from one terminal
of a battery through the copper wire and bulb to the other
terminal of the battery. As the electrons move, their energy
is transformed into light. Your brain and the nerves in your
body that tell your arm and leg muscles to move also use
electric energy.
Combined Kinetic Energy
and Potential Energy
Your school is part of an education system. Earth is part
of the solar system. A system is a collection of parts that
interact and act together as a whole. In science, everything
that is not in a given system is the environment. For
example, a hockey player, the hockey stick, the hockey puck,
and the ice under the player can be considered a system.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Mechanical Energy
Suppose the hockey player hits the hockey puck into the
air. Does the puck have kinetic energy or potential energy?
It has mass and motion, so it has kinetic energy. It also has
height above Earth, so it has gravitational potential energy.
Scientists often study the energy of systems, such as the one
described above. The sum of the potential energy and the kinetic
energy in a system is mechanical energy. You might think of
mechanical energy as the ability to move another object.
What happens when the hockey puck hits the net? The net
moves. The hockey puck has mechanical energy that causes
another object to move.
Thermal Energy
Even when the hockey puck is lying on the floor with no
obvious motion, the particles that make up the solid puck
are in motion. The particles vibrate back and forth in place.
Therefore, the particles have kinetic energy. The particles also
have potential energy because of attractive forces between
the particles. An object’s thermal energy is the sum of the kinetic
energy and the potential energy of the particles that make up the
object. Thermal energy of an object increases when the
potential energy, the kinetic energy, or both increase.
C352_001_006_RE_L1_889408.indd 3
3/8/10 11:15:59 AM
Energy Carried by Waves
When a raindrop falls into a still pool of water, the
raindrop disturbs the water’s surface. It produces waves that
move away from the place where the raindrop hit. A wave is
a disturbance that transfers energy from one place to another without
transferring matter. Energy, not matter, moves outward from
the point where the raindrop hits the water.
Sound Energy
When the raindrop hits the water, it disturbs the surface
of the water, and it also disturbs the air. It creates a sound
wave in the air similar to water waves. Sound waves move
through matter. Each wave travels from particle to particle as
the particles bump into each other, much like falling
dominoes. Sound energy is energy carried by sound waves.
As a sound wave travels, it eventually reaches your ear.
The sound energy moves tiny hairs inside your ear. This
movement is transformed into an electric signal that travels
to your brain. Your brain interprets the electric signal as the
sound of a water splash.
Radiant Energy
Electromagnetic Waves
Electric field
Magnetic field
Electron
Direction
of travel
Wavelength
Gamma
rays
10-14
400
X-rays
10-12
Ultraviolet
rays
10-10
Infrared
rays
Radar
10-8 10-6 10-4
Visible Light
500
10-2
600
FM
1
TV
Shortwave
AM
102
104
Wavelength (meters)
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Have you ever wondered what light is? Light is a form of
energy carried by electromagnetic waves—electric and
magnetic waves moving perpendicularly to one another, as
shown in the figure. The energy carried by electromagnetic waves is
radiant energy.
700
Wavelength (nanometers)
C352_001_006_RE_L1_889408.indd 4
3/8/10 11:16:10 AM
Electromagnetic Waves Waves that travel through matter and
through spaces with little or no matter, such as outer space, are
called electromagnetic waves. Electromagnetic waves often are
described by their wavelengths. Wavelength is the distance
from one point on a wave to the nearest point just like it.
Other Forms of Radiant Energy Visible light is only one
form of radiant energy. Gamma rays and X-rays are
electromagnetic waves with very short wavelengths. Gamma
rays and X-rays often are used in medical procedures.
Ultraviolet rays have wavelengths that are a little shorter
than those of light. This form of radiant energy is what
causes your sunburn.
Copyright © Glencoe/McGraw-Hill, a division of The McGraw-Hill Companies, Inc.
Infrared rays are the form of energy used by many
television remote controls to change channels. They also
provide the warmth you feel when the Sun shines on you.
Radar, television, and radio waves have long wavelengths
compared to the wavelength of visible light.
C352_001_006_RE_L1_889408.indd 5
3/8/10 11:16:13 AM