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Chapter 15
Science Journal Entry 22
• Describe two types of energy (energy
sources for humans) and what you
believe are the advantages and
disadvantages of each type.
Science Journal Entry 23
• Saving space between each question,
create three interview questions about
energy and types of energy.
• Recording the name of the person that
you have chosen to interview, record
their answers to those 3 questions.
The Relationship of Work and Energy
• Energy is the ability to do work. Energy is
transferred by a force moving an object
through a distance. So when work is done
on an object, energy is transferred to that
object. Work is therefore the transfer of
energy. Work and energy are measured in
joules (J). Recall that a joule is equal to one
newton-meter which is the amount of work
done to move an object one meter with one
newton of force.
Kinetic Energy
• Kinetic Energy is the energy of motion.
Kinetic energy of any moving object depends
upon its mass and speed.
• Kinetic Energy (KE) = ½ mv2
• To Calculate the kinetic energy of an object in
joules, multiply ½ by the object’s mass in
kilograms (kg) and the square of its speed (v)
in meters per second.
Potential Energy
• Potential energy is energy that is stored as a
result of position or shape. Two forms of
potential energy are gravitational potential
energy and elastic potential energy.
• Potential energy that depends upon an object’s
height is called gravitational energy. When an
object’s height is increased (placed at a higher
elevation), the object’s gravitational potential
energy is also increased.
• 3:44
Gravitational Potential Energy
• Gravitational Potential Energy depends on the
mass, its height, and the acceleration due to
gravity. The gravitational energy an object gains is
equal to its weight (mg) multiplied by its height
Potential Energy (PE) = mgh
• Gravitational potential energy is expressed in
joules, the mass is expressed in kilograms, and the
height in meters. The acceleration due to gravity,
g, has a value in SI units of 9.8 m/s2. Height is
measured from the ground or floor or some other
reference level.
aF0qvxLz8TocuIwUmLgrBkhS 2:45 coaster
Doing the Math
• Example Problem:
• A diver at the top of a 10 meter high
diving platform has a mass of 50
kilograms. What is the diver’s potential
energy? The formula is PE = mgh
• What is used for the g in the equation?
• What would be the total gravitational
potential energy if the diver was
standing at ground level?
Elastic Potential Energy
• Elastic potential energy is the potential energy of
an object that is stretched or compressed.
• A rubber band when stretched has elastic potential
energy that immediately becomes kinetic energy
when the rubber band is released.
• Another example of elastic potential energy would
be the strings of a musical instrument. A basketball
has elastic potential energy since the compressed
air in the ball forces the ball to spring back.
F0qvxLz8TocuIwUmLgrBkhS 1:22 Wilie
Mechanical Energy
• Mechanical Energy is the sum of an
object’s potential and kinetic energy.
This energy is associated with the
motion and position of everyday
objects and is not limited to
Thermal Energy
• Thermal Energy is the total potential
and kinetic energy of all the
microscopic particles in an object.
Matter contains atoms that are
always in random motion. When an
object’s atoms move faster, the
object becomes warmer and has a
greater thermal energy.
Chemical Energy
• Chemical Energy is the energy stored in
chemical bonds. This energy is released
when the chemical bonds are broken.
All chemical compounds store energy.
Wood for campfires, coal and gasoline
are all examples of substances that have
the stored energy released by burning.
Electrical Energy
• Electrical Energy is the energy
associated with electric charges.
Batteries convert chemical energy to
electrical energy to operate
flashlights and calculators. In nature
lightning bolts are produced by
electrical energy.
Electromagnetic Energy
• Electromagnetic Energy is a form of
energy that travels through space in the
form of waves. Electromagnetic energy
reaches earth as it is radiated by the
sun. This radiation is able to travel
through space not needing a medium to
travel. Visible light and x-rays are two
forms of electromagnetic energy.
Many Forms of Radiation
• All forms of electromagnetic
radiation collectively are called
the electromagnetic spectrum.
Electromagnetic waves such as
radio waves are used in
communication since they can
move long distances through air
and space.
Electromagnetic Spectrum
Nuclear Energy
• Nuclear Energy is the energy stored in atomic
nuclei. The nucleus of an atom is held together
by strong and weak nuclear forces giving it great
potential energy.
• Nuclear energy is released by two processes:
fission and fusion. Energy is released in fission by
splitting apart atomic nuclei. It is the process
used by nuclear power plants to generate
electricity. The sun uses the process of fusion to
generate energy. Fusion occurs when less
massive nuclei combine to form a more massive
Quick Review
• What type of energy is used in
• What type of energy is used within the
• What type of energy is evident in
lightning bolts?
• All forms of energy can be converted
into other forms of energy.