Transcript Nature of Energy

Nature of Energy
Pgs. 402 - 414
The Mysterious Everything
What is this stuff?
Whatever happens is caused by it. Whatever is, is made up of it.
You need it, you are made up of it.
Everything needs it. Everything is it. It is everything!
You need it to run, to walk, to sit,
to think, to sleep, "perchance to dream", to eat, "perchance to belch."
You use it constantly, every moment, awake or asleep.
You can't get mad without it.
You can't get glad without it
You can't get anything without it.
It makes the wind blow, rain fall and lightning zap and thunder.
It "feeds" volcanoes and earthquakes. It drives tidal waves, typhoons, and tornadoes.
It powers the universe!
It is the Mysterious Everything.
Let's call it ME for short.
WHAT IS THIS STUFF?
What is energy?
 Energy is the ability to
do work or cause
change
 Work happens when a
force moves an object
through a distance
 Force is a push or pull
 Work can also be
thought of as the
transfer of energy.
A joule is the
metric unit used for
energy and work!
Transferring Energy
 Everything around you has energy.
 You notice energy when a change takes
place.
 Anytime a change occurs, energy is
transferred from one object to another.
Transfer of Energy Examples
 Someone’s foot hits the floor and you
hear a sound.
 The top of your desk becomes warm
when the sun shines on it.
 A CD player is plugged up and turned on.
The CD turns, and you hear music. 3
energy transfers have occurred.
Electrical - Mechanical Sound
Kinetic Energy
 2 kinds of energy
 Kinetic energy (energy being transferred)
 Potential energy (energy being stored)
 Kinetic energy is energy in motion
 An object’s kinetic energy depends on its
mass and velocity
 Mass – amount of matter in an object
 Velocity – speed in a given direction
Kinetic energy needs
mass & velocity?
 If the mass of an object increases, its kinetic
energy increases.
 If the velocity of an object increases, its kinetic
energy increases.
 All energy and work are measured in joules.
Marble Experiment
Calculating Kinetic Energy
Kinetic Energy = Mass x Velocity2
2
3 x 9 = 27 = 13.5 joules
2
2
Plug in the following values and see how kinetic energy
changes.
Mass = 3, velocity = 6
Mass = 6, velocity = 3
 CHECKPOINT 
 Which has the greatest kinetic energy: a
motorcycle moving at 30 km/hour, a fourdoor car moving at 30 km/hour, or a truck
sitting on top of a hill?
Potential Energy
 Energy that is stored and
NOT IN MOTION
 2 types of potential energy
 Elastic potential energy –
potential energy associated
with objects that can be
stretched or compressed
 Gravitational potential
energy – potential energy
associated with height
Elastic Potential Energy
 CHECKPOINT 
 What is the unit for work and energy?
Joule or
Newton-meter
Calculating Gravitational
Potential Energy
 GPE = weight x height (unit is joules)
 The greater the weight of an object or the
greater the height it is lifted, the greater is
its GPE
 If you don’t have weight but have the
mass, you must multiply the mass by 9.8
m/s2 in order to convert it to the weight in
newtons.
 CHECKPOINT 
 Describe how the ball experiment is an
example of gravitational potential energy.
Let’s Review!
Different Forms of Energy
1.
2.
3.
4.
5.
Mechanical Energy
Thermal Energy
Chemical Energy
Electrical Energy
Electromagnetic
Energy
6. Nuclear Energy
 Energy transformations occur constantly all
around you.
 Many machines are devices that transform
energy from one form to another.
Example: An automobile engine transforms
the chemical energy in gasoline into energy
of motion.
Mechanical Energy
 Energy associated with the motion or
position of an object
 Can be potential or kinetic
Thermal Energy
 Energy of particles in
an object
 When particles move
faster, more heat is
generated
 When particles move
slower, less heat is
generated
Food Coloring Experiment
HOW THERMAL ENERGY MOVES
 Thermal energy only moves from
something warm to something cool.
Example: Hot chocolate’s thermal energy
moves from the cup to the cooler spoon
and to the cooler air around it.
Chemical Energy
 Potential energy stored in chemical
bonds that hold chemical compounds
together
 In your body, the transformation of chemical
to kinetic energy occurs in muscle cells.
Electrical Energy
 Moving electric charges producing
electricity
Generating Electrical Energy
 The enormous amount of electrical energy
that is used everyday is generated by power
plants.
 Every power plant works on the same
principle---energy is used to turn a large
generator.
 A generator is a device that transforms
kinetic energy into electrical energy.
 In fossil fuel power plants, coal, oil, or
natural gas is burned to boil water.
 As the hot water boils, steam rushes
through a turbine, a device which contains a
set of narrowly spaced fan blades. The
steam pushes on the fan blades and turns
the turbine. The turbine, in turn, rotates a
shaft in the generator to produce electricity.
Electromagnetic Energy
 Has both electric properties and magnetic
properties
 Travels in waves and includes microwaves,
ultraviolet radiation, infrared radiation, and
visible light
Nuclear Energy
 Type of potential energy stored in the
nucleus of an atom
 One type of nuclear energy is called
nuclear fission (nucleus splits apart)
 Another type of nuclear energy is called
nuclear fusion (many nuclei fuse
together)
Nuclear
fission
Nuclear
fusion