Download Conservation of Energy

Nature of Energy
 Energy is all around you!
 You can hear energy as sound.
 You can see energy as light.
 And you can feel it as wind.
Energy is usually described
as kinetic or potential
Thermal or Heat Energy
 The internal motion of the
atoms is called heat energy,
because moving particles
produce heat.
 Heat energy can be produced
by friction.
 Heat energy causes changes
in temperature and phase of
any form of matter.
Chemical Energy
 Chemical Energy is required to bond
atoms together.
 And when bonds are broken, energy is
released.
 Fuel and food are forms
of stored chemical energy
Electromagnetic Energy
 Light is a form of electromagnetic energy.
 Each color of light (Roy G Biv) represents a
different amount of electromagnetic energy.
 Electromagnetic Energy is also carried by X-rays,
radio waves, and laser light.
Electromagnetic Spectrum
Increasing Energy
Electromagnetic
Energy
 Power lines carry
electromagnetic energy into your
home in the form of electricity.
Nuclear Energy
 The nucleus of an atom is the source of
nuclear energy.
 When the nucleus splits (fission), nuclear
energy is released in the form of heat energy
and light energy.
 Nuclear energy is also released when nuclei
collide at high speeds and join (fuse).
Nuclear Power Plant
Nuclear Energy
The sun’s
energy is
produced from a
nuclear fusion
reaction in which
hydrogen nuclei
fuse to form
helium nuclei.
Mechanical Energy
 Mechanical energy is due to
the position and motion of
the object.
 When work is done to an
object, it acquires energy.
The energy it acquires is
known as mechanical
energy.
Mechanical Energy
 What happens to the mechanical
energy of an apple as it falls from a
tree?
Mechanical Energy
 As the apple falls to the ground, its height
decreases.
 Therefore, its GPE decreases. Potential
energy that is dependent on height is
called gravitational potential energy.
 The potential energy is not lost… it is
converted into kinetic energy as the
velocity of the apple increases.
 What happens to the mechanical
energy?
Mechanical Energy
 The mechanical energy does not change
because the loss in potential energy is
simply transferred into kinetic energy.
 The energy in the system remains
constant!!
Swinging Along
 Think about the changes in energy when
you are on a swing…
 At what point do you have the most
potential energy?
 At what point do you have the most
kinetic energy?
 What happens to the mechanical
energy?
Conservation of Energy
 Energy is transformed… not destroyed!!
The Law of Conservation of Energy
• The law of conservation of energy
states that energy cannot be
created or destroyed.
• Energy can be changed from one
form to another. Changes in the
form of energy are called
energy conversions.
Energy Conversion
Examples
The Law of Conservation of Energy
• Even when energy changes form from
electrical to thermal and other energy forms
as in the hair
dryer shown
energy is never
destroyed.
The Law of Conservation
of Energy
 The Law of Conservation of Energy
states that energy cannot be created or
destroyed.
 The big picture… the total energy in the
universe remains constant.
Changing Forms of Energy
 Energy is most noticeable as it
transforms from one type to another.
 What are some examples of transforming
electrical energy?
 A lightbulb
 A hair dryer
Potential to Kinetic
 The most common energy
conversion is between potential
and kinetic energy.
 All forms of energy can be in either
of two states:
 Kinetic is the energy of motion.
 Potential is stored energy
Changing forms of Energy
 An example of transforming chemical
energy is a car engine.
 Chemical potential energy in gasoline is
transformed into kinetic energy of the car
as it moves!!
Energy transfer
Photosynthesis
 Photosynthesis
changes light energy
into food (chemical)
energy.
 Plants convert the
energy of sunlight into
the energy of chemical
bonds of carbohydrates
http://www.eia.doe.gov/kids/energyfacts/source
s/renewable/images/photosynthesis1.gif
Energy conversion
Digestion is the process in
the body that breaks these
chemical bonds and
releases the chemical
energy in foods
This chemical potential
energy is changed into
kinetic energy as your body
moves
Conserving Energy
 When you “use” energy
by turning on a light, you
are really converting
energy from one form
(electricity) to other forms
(light and heat).
How does the bulb light up?
What forms of energy are
seen?
 The bulb gets its energy from
the battery.
 There is chemical energy in
the battery
 Electrical energy in the wires
 Thermal energy in the bulb
filament
 Light energy and thermal
energy seen from the bulb.
 Energy changes form to light
the bulb.
Conserving Energy
 Electric power plants don’t make electrical energy.
 Energy cannot be created.
 Energy CAN be converted from other forms of
energy such as chemical, solar, or nuclear energy.
Conserving Energy
 An average electric
power plant puts out
1,000,000 kwh of
electrical energy per
hour.
 That means 120 power
plants are burning up
resources each hour
just to run light bulbs!
Solar Energy
• Solar Power, along with wind and hydroelectric
account for most of the renewable energy source
available to use.
• Solar energy can be collected by humans
through photovoltaics or solar panels.
 What do the photovoltaic and the wheat
plant, shown in the images below, have in
common?
 Photovoltaic
Wheat
 ANSWER: They both convert sunlight,
(electromagnetic energy), into chemical
potential energy
 The photovoltaic absorbs solar energy and
stores it as chemical potential energy in
batteries.
 The leaves of the wheat plant absorb solar
energy which is (mainly) stored as chemical
potential energy in compounds called
carbohydrates.
Kinetic Energy
 The faster an object moves, the more
kinetic energy it has.
 The greater the mass of a moving
object, the more kinetic energy it has.
 Kinetic energy depends on both mass
and velocity.
Kinetic Energy
K.E. = mass x velocity
2
What has a greater effect on kinetic energy,
mass or velocity? Why?
the velocity because it is being squared so
it is increasing by a factor of 4
Potential Energy
 “The bigger they are the harder they
fall” is not just a saying. It’s true.
Objects with more mass have greater
P.E.
 The formula to find P.E. is
P.E. = Weight X Height.
Ball slows down
Ball speeds up
At the point of maximum potential energy,
the car has minimum kinetic energy.