Transcript 20170209181827x

DIRECTIONS
• Copy only what is in green
• ISN pg. 35: Energy Conversion & Conservation,
book pg. 453-459
– Next week we will do more with the math part on
conservation of energy and I’ll explain in more
details
• Do not interact on page 34
• No summary for this first set of notes
Energy Conversion
• Energy can be converted from one form to
another, known as energy conversion
• Examples:
– Wind-up toys: store elastic PE in spring, when
released the PE is converted to KE and the toy
moves
– Light bulbs: convert electrical energy to thermal
and electromagnetic energy
– See more on page 454 of book
Conservation of Energy
• The law of conservation of energy states that
energy cannot be created or destroyed
– Energy can be converted from one form to
another
– In a closed system, the amount of energy present
at the beginning of a process is the same as the
amount of energy at the end
– See example on page 455
Energy Conversions
• Gravitational potential energy of an object is
converted to the kinetic energy of motion as
the object falls
• Conversions between KE and PE can happen in
both directions
Energy Conversion in Pendulums
• Rope swing is an example of a pendulum.
– Pendulum consists of a weight swinging back and
forth from a rope or string
– KE and PE undergo constant conversion as a
pendulum swings.
– At HIGHEST point in swing, pendulum is
momentarily motionless: the weight at the end
has zero KE and maximum PE
– As is swings downward, PE is converted to KE
– At the bottom of the swing, the pendulum has
maximum KE and zero PE
Energy Conversion in the Pole Vault
• Pole-vaulter’s KE is partially converted into
elastic PE as the pole bends. It springs back
into shape, propelling the pole-vaulter upward
– As he soars KE decreases while he gains
gravitational PE
– At the highest point, gravitational PE begins to
convert back to KE
Energy Conversion Calculations
• Conservation of Mechanical Energy
– When friction is small enough to be ignored
• Math Practice pg. 458
Energy and Mass
• Einstein (1879-1955)
– Developed theory of relativity
• E = mc2
(Energy = mass X c-the speed of light squared)
• Einstein’s equation, E =mc2 says that energy
and mass are equivalent and can be
converted into each other
– In other words: energy is released as matter is
destroyed, and matter can be created from
energy
Energy and Mass
• In nuclear fission and fusion reactions, large
amounts of energy are released by the
destruction of very small amounts of matter.
• The law of conservation of energy has been
modified to say that mass and energy
together are always conserved
Directions
• Notes part 2- TURN THE PAGE
• ISN pg. 37: Energy Resources, book pg. 462466
• Copy only what is in green
• You do not have to write a summary
• You DO NEED to interact on page 36
Nonrenewable Energy Resources
• Nonrenewable energy resources- exist in
limited quantities, once used, cannot be
replaced except over the course of millions of
years
• Examples: oil, natural gas, coal, and uranium
• Fossil fuels: oil, natural gas, and coal
– Creates pollution
• Many of these resources are being used faster
than they can be replaced
Nonrenewable Energy Resources
Renewable Energy Resources
• Renewable energy resources- resources that
can be replaced in a relatively short period of
time
– Most originate directly/indirectly from the sun
– Example: hydroelectric, solar, geothermal, wind,
biomass
– Challenge is to find efficient ways to make these
energy resources inexpensive and convenient
Renewable Energy Resources
Hydroelectric Energy
• Hydroelectric energy- energy obtained from
flowing water
• As water flows downhill, its gravitational PE is
converted into KE which can be used to turn
turbines that are connected to electric
generators
• Many hydroelectric power plants rely on dams
– Cause a few environmental problems (fish
spawning)
Hydroelectric Energy
Solar Energy
• Solar energy- sunlight that is converted into
usable energy
– nonpolluting
Geothermal Energy
• Geothermal energythermal energy beneath
Earth’s surface
• Steam is used to drive
electric generators
• Nonpolluting
• Not widely available
Other Renewable Resources
• Biomass energy- the chemical energy stored
in living things
– Can be converted directly into thermal energy (ex:
wood burning)
• Hydrogen fuel cell- generates electricity by
reacting hydrogen with oxygen
– End product is water, nonpolluting
Renewable vs. Nonrenewable
Conserving Energy Resources
• Energy resources can be conserved by
reducing energy needs and by increasing the
efficiency of energy use
• Energy conservation- finding ways to use less
energy or to use energy more efficiently
– Turn of lights when not in use
– Energy efficient products (appliances, cars, light
bulbs)
IF YOU STILL HAVE TIME….
• Check out the TedEd link to see some
examples on energy transformations. (Things
can get a little confusing with all the energy
stuff going on in this chapter).
• I also recommend reading over pages 453-466