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Energy
SC Physical Science Standards
Standard PS-6: The student will
demonstrate an understanding of the
nature, conservation, and transformation
of energy.
PS-6.1
Explain how the law of conservation of energy
applies to the transformation of various forms of
energy (including mechanical energy, electrical
energy, chemical energy, light energy, sound
energy, and thermal energy).
PS-6.2
Explain the factors that determine potential and
kinetic energy and the transformation of one to the
other.
Energy: The ability to do work or cause
change.
James Prescott Joule
Studied
transformations
of energy,
devised many of
the energy
calculations we
use today.
 Joule (J)- SI
unit of energy.
Law of Conservation of Energy
Energy may
change from
one form to
another, but
the total
amount of
energy
NEVER
changes.
FORMS OF ENERGY
1. Mechanical - Energy due to something’s position or
motion. It is either potential, kinetic, or the sum of the
two.
2. Chemical - Energy associated with chemical bonds
between atoms or ions. Transformations occur during
chemical reactions.
3. Nuclear - Energy associated with reactions involving
the nucleus of the atom.
4. Electrical - Energy associated with current and voltage.
5. Thermal (Heat) - Energy associated with movement of
particles.
6. Light - Energy associated with electromagnetic waves.
7. Sound - Energy associated with longitudinal waves.
How to Remember the Forms of Energy
My children never eat tiny little snots.
Mechanical:
• Potential Energy – Energy is greater when height above
ground is greater, due to gravity.
– Energy is greater when weight is
greater, due to gravity.
• Kinetic Energy – Energy is greater when speed is
greater, due to motion.
– Energy is greater when mass is
greater, due to motion.
An example:
Potential & Kinetic Energy
As the
baseball's
height
increases the
potential
energy
increases
and vice
versa
(potential).
Potential Energy
• Stored energy
• Energy of position
• The amount of usable energy in a
body at rest
• Sometimes called
GRAVITATIONAL POTENTIAL
ENERGY
Potential Energy
Can be calculated mathematically
• PE = (weight) (height) or
• PEgrav = mass • gravity • height
m = mass of the object
h = height of the object above
the ground
g = gravitational field strength
(9.8 m/s2 on Earth)
Potential Energy
Can be increased by:
• Increasing height
• Increasing mass
Kinetic Energy
• Energy of motion
• Energy an object has because it is
moving
Can be calculated mathematically
KE = ½ mv2
• KE = kinetic energy in joules (J)
m = mass of the object in kilograms
(kg)
v = the velocity of the object in
meters per second (ms-1 or m/s).
Kinetic energy can be increased by:
• Increasing mass
• Increasing speed
KE & PE Interactions
• Generally, as the potential energy of
an object increases, its kinetic
energy decreases.
Transformation:
• The different types of energy can
change from one form to another
without changing the total amount of
energy…
• Here are some examples:
What energy transformations are
taking place?
Electrical to
light / thermal
Chemical
to heat
Chemical to
light / sound
Kinetic to
electrical
Nuclear to
electrical
Radiant to
electrical
The Law of Conservation of Energy
energy cannot be created or
destroyed; it can only change forms
Following Energy’s Trail
• If energy is conserved, why do
objects that are moving eventually
stop (seem to lose energy)?
– The energy is converted to other
forms
Converting Mass into Energy
• Two processes convert a small
amount of mass into a large amount
of energy
– Nuclear fission – the splitting of an
atomic nuclei
Nuclear fusion – the combining of
small nuclei
• This is what powers the sun
Energy and The Human Body
• We get our energy from the foods we
eat (chemical potential energy)
• We convert that energy to kinetic
energy, sound energy, & thermal
energy
• The energy we get from foods is
measured in Calories
– 1 Calorie = 4,184J
ENERGY TRANSFORMATIONS
Example #1
• An object on the ground has zero potential
energy.
• Lift it to some height, it now has PE equal to the
work it took to lift it to that height. Its PE
depends on its weight and height above the
ground.
• Drop the object and the PE is transformed to
kinetic energy as it speeds up due to the
attraction of gravity. However, the total energy
remains the same, throughout the
transformation.
• Just before the object hits the ground, most of
the PE is now KE. It has lost the PE because its
height has returned to nearly zero.
• When it hits the ground, some of the KE will be
transformed again to sound energy and thermal
energy as the particles speed up when they
strike the ground.
Example #2
• A swinging pendulum has mechanical energy
(both potential and kinetic energy are involved in
the swing).
• At the top of the swing PE is greatest; and
depends on its height and weight.
• KE is greatest at the bottom of the swing
because the speed is greatest.
• Between top and bottom, PE is transforming to
KE because of the changes in both height and
motion.
• Eventually the pendulum comes to a stop
because of friction.
• Friction transforms mechanical energy to
thermal energy.
Example #3
• A light bulb is glowing in an electric circuit
powered by a battery.
• Chemical energy transforms to electrical
energy.
• Electrical energy (electrons) flows through
the bulb transforming to light and thermal
energy due to the resistance of the filament
to the movement of the electrons through the
wire.
• The total energy from the chemical reaction
of the battery is equal to the total energy that
it transforms into in the form of light and heat
through the bulb and through the wires.
Example #4
• A baseball is thrown from the catcher to the first
baseman.
• The catcher transforms chemical energy from
food to mechanical energy when moving her arm
to throw the ball.
• The work done on the ball converts the moving
(kinetic) energy of her arm to KE of the moving
ball.
• When the first baseman catches the ball, the ball
does work on his hand and glove, giving them
some mechanical energy.
• The ball also moves particles in the glove upon
impact, transforming KE to thermal energy when
it is caught.
• The player catching the ball absorbs the energy
of the ball and this energy is turned to heat.
• The total heat energy produced in the first
baseman is equal to the energy used to throw the
ball by the catcher.
Other Examples…
• A swing- Kinetic energy to Potential
energy and back again to Kinetic
• Friction- Mechanical energy to
Thermal energy
• Nuclear Fusion and Fission- Mass
becomes energy
• Digestion- Chemical bond energy to
thermal energy, mechanical energy,
etc. depending on your bodies need
Energy Interactive Notes
Tuesday, February 14, 2012
_________________: The ability to do work or cause change.
James Prescott Joule Law of Conservation of Energy - Energy may change from one ___________ to another, but the ________
amount of energy never changes.
How to Remember the Forms of Energy - My children never eat tiny little snots.
Mechanical:
•
•
•
•
Potential Energy –
Energy is ___________ when height above ground is greater, due to ___________.
–
Energy is greater when ___________ is greater, due to gravity.
Kinetic Energy –
Energy is greater when ___________ is greater, due to ___________.
–
Energy is greater when ___________ is greater, due to motion.
Potential Energy
•
___________ energy
•
Energy of ___________
•
The amount of usable energy in a body at ___________
•
Sometimes called GRAVITATIONAL _________________________________ ENERGY
•
Potential Energy - PE = (weight) (height) or PEgrav = mass • gravity • height
•
___________ = mass of the object
•
___________ = height of the object
•
___________ = gravitational field strength (9.8 m/s2 on Earth)
Can be increased by:
•
Increasing ___________
•
Increasing ___________
Kinetic Energy
•
Energy of ___________
•
Energy an object has because it is ___________