ENERGY AND POWER

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ENERGY AND POWER

• Chapter 13

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The Nature of EnergySection 13 - 1
I. What is Energy? - the ability to do work or
cause change. Remember - Work is force over
a distance. - or the transfer of energy.
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II. Kinetic Energy
(There are two general kinds of energy. -
kinetic potential) A. Kinetic Energy is the
energy of motion. 1. Moving objects can do work
so they must have energy. 2.
Kinetos - Greek for moving
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(II. Kinetic Energy)
B. Mass Velocity - influence an
objects kinetic energy - ex. - think of a
bowling ball a golf ball Which would you
need to exert more force on to move?
Why?? Greater force greater energy
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III. Calculating Kinetic Energy
A. Kinetic energy mass x velocity2 2 -
what would have a greater affect on kinetic
energy - doubling the mass or doubling the
velocity?
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List the order of the 3 vehicles by increasing
K.E.
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IV. Potential Energy
A. Energy that is stored and held in
readiness. B. Two types of potential
energy 1. Elastic 2. Gravitational
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Elastic potential energy -P.E. that is
associated with things can be stretched or
compressed.
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Gravitational Potential Energy
Energy dependent on height
GPA
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A rock posed for a fall has potential energy.
How did it get its potential energy?
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Different Forms Of Energy
Some of the major forms of energy
are Mechanical Thermal Chemical
Electrical Electromagnetic Nuclear
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Mechanical Energy
M.E. is associated with the motion or position of
an object. M.E. can occur as kinetic or potential
energy.
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Mechanical Energy
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Mechanical Energy
What illustrates mechanical energy in this
picture?
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Thermal Energy
-All matter is made up of particles. -These
particles have both kinetic potential energy -
due to their arrangement motion. - Thermal
energy is the total energy of the particles in an
object.
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Thermal Energy
When the thermal energy of an object increases,
its particles move faster, making it feel warmer.
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Chemical Energy
Chemical energy is potential energy stored in
chemical bonds that hold chemical compounds
together. - stored in - foods -
matches -cells of your body
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Chemical Energy
Food is chemical energy that is converted to
mechanical energy.
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Electrical Energy
Moving electric charges produce electricity and
the energy they carry is electrical
energy. -Sources - Power lines, batteries -
lightning, static electricity
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Electrical energy
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Electromagnetic Energy
E.M.E. energy travels in waves. These waves have
some electrical properties and some magnetic.
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Electromagnetic CT scan
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Light is E.M.E.
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Laser light is E.M.E.
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Nuclear Energy

• Nuclear energy is stored in the nucleus of an
  atom and is released during nuclear reactions
• These reactions release
• a tremendous amount
• of energy

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2 Types of nuclear reactions

• Nuclear Fission when a nucleus splits
• Example
• nuclear power plants use fission to produce
  electricity

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Nuclear Fusion when a nuclei fuse (join
together) Occurs in the sun and other
stars
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The birth of a star - nuclear fusion takes place
in stars.
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13 - 2Energy Conversion Conservation
Niagara Falls generates electricity.
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Conversions Between Forms of Energy

• Energy Conversion a change from one form of
  energy to another
• Also referred to as energy transformation
• Most forms of energy can be converted into any
  other form

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Energy Conversions - Electrical to
electromagnetic.
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Energy Conversions - Chemical to thermal.
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Energy Conversions - Chemical to mechanical.
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Kinetic and Potential Energy

• Most common conversion is potential to kinetic
  energy.
• Ex Stretching a rubber band gives it elastic
  potential energy. When the rubber band is
  moving, it has kinetic energy. The potential
  energy of the stretched rubber band is converted
  to the kinetic energy of the moving rubber band.

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Energy conversions enable this athlete to vault
into the air. What conversions are taking place?
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Energy Conversion

• Juggling
• Any object that rises or falls experiences a
  change in its kinetic gravitation potential
  energy.

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At what point(s) does K.E. to zero?
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Energy Conversions

• Waterfall
• The water at the top of the falls has
  gravitational potential energy (because it is
  higher than the bottom of the falls).
• But as the water falls, its height decreases, so
  it loses potential energy.
• At the same time its kinetic energy increases
  because its velocity increases.
• So, the P.E. is converted into K.E.

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What is wrong with this picture?
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Energy Conversions

• Pole Vault
• As a pole vaulter runs, he has K.E because he is
  moving.
• His K.E is converted to E.P.E as his pole bends
  and absorbs energy.
• As the pole straightens, E.P.E is converted to
  G.P.E as the vaulter is lifted into the air.
• G.P.E is converted to K.E as the vaulter clears
  the bar and falls to the mat.

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Energy Conversions

• Pendulum
• A continuous conversion of K.E and P.E takes
  place in a pendulum.

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(Gravitational)
(Gravitational)
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Conservation of Energy

• Law of Conservation of Energy states that energy
  cannot be created or destroyed.
• When one form of energy is converted to another,
  no energy is destroyed in the process.

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Conservation of Energy

• Question
• If you set a pendulum in motion, does it remain
  in motion forever?
• No, it will not. All energy can be accounted
  for. So, where did it go?
• Converted to other forms

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Energy and Friction

• So, what happens to the K.E of the pendulum?
• When objects experience friction, the motion
  (the K.E) of the atoms or molecules
  increases?thermal energy increases!
• So, mechanical energy of the moving pendulum is
  converted to thermal energy.
• The pendulum slows down but its energy is not
  destroyed!

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Now, can you explain why no machine is 100
efficient?

• In a machine, work output is always less than
  work input because the energy wasted on
  friction is converted to thermal energy in a
  machine.

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Energy Matter

• In nuclear reactions, where huge amounts of
  energy are produced by destroying tiny amounts of
  matter.
• Energy alone is not conserved but matter energy
  together are conserved!
• Remember E mc2

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Conserving Energy

• Conserving energy means saving energy, or not
  wasting it.
• Dont confuse this with the Law of Conservation
  of Energy which refers to a quantity that remains
  constant.
• Remember, in science, energy is always conserved
  because its total quantity does not change.

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Sec 3 Energy Conversions Fossil Fuels

• Fossil Fuels contain energy that came from the
  sun.
• Coal, Petroleum, natural gas
• Created millions of years ago from ancient plants
  animals.

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This ancient forest was part of the Carboniferous
Period.
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Use of Fossil Fuels

• Fossil fuels can be burned to release the
  potential chemical energy stored millions of
  years ago. (Rich in carbon compounds)
• Process of burning fuel combustion.

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Coal - a FOSSIL fuel. The carbon remains of
plants deposited during the Carboniferous Period.
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Exploring Energy Conversions
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Ancient plants and animals convert
electromagnetic energy from the sun into stored
chemical energy.
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The remains of plants animals become coal over
millions of years.
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Stored chemical energy in coal is converted to
thermal energy to make steam. Thermal energy is
converted to mechanical energy as the steam turns
turbines. Mechanical energy is converted into
electrical energy as the moving turbines generate
electricity.
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Electrical energy is converted to thermal energy
in a toaster.
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Sec 4 Power

• Power is the rate at which work is done or the
  amount of work done in a unit of time.
• Power Work / Time
• Power (Force x Distance) / Time

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• Work is measured in joules, time in seconds, the
  unit of power is the joule. So, the unit for
  power is Joule/second (J/s).
• J/s is also called the watt (W).
• 1 watt 1 J/s
• 1kW 1,000 watts
• Washing machines use about 1kW when its running.

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Power Energy

• Recall that work is the transfer of energy.
• So, power can be considered the rate at which
  energy is transferred from one object to another
  or converted to one form to another.
• For this reason, power is not limited to
  situations in which objects are moved.
• Power can be found whenever energy is being
  transferred or converted.

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Example Comparing Light Bulbs

• 100 W light bulb is much brighter than a 40 W
  light bulb.
• A 100 W light bulb converts
• electrical energy at a rate
• of 100 J each second
• A 100 W bulb is brighter
• because it gives off more
• energy per second than a
• 40 W.

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Horsepower

• James Watt used the term horsepower to
  advertise the advantages of his steam engine.
• He defined 1 horsepower as the amount of work a
  horse does to lift a 33,000-pound weight a
  distance of 1 foot in 1 minute.

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One horsepower 746 watts. This is not an SI
unit.
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THE END