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Energy and Power
The Nature of Energy
What is energy?
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The ability to work or cause change is called energy.
When an object or organism does work on another object,
some of its energy is transferred to that object.
Think of work as the transfer of energy.
Work = Force x Distance
There are 2 types of energy: Kinetic and Potential
What is a joule?
The amount of work you do when you
exert a force of 1 newton to move an
object a distance of 1 meter.
 Weight is measured in newtons and
Height is measured in meters, the unit of
energy is the newton-meter.
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Kinetic Energy
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The energy of motion is called kinetic energy.
Kinetic: Greek word kinetos =“Moving”
Kinetic energy of an object depends on both its
mass and its velocity.
Kinetic energy increase as mass increases.
(golf and bowling ball)
Kinetic energy increases as mass and velocity
increase.
Calculating Kinetic Energy
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Changing the velocity of an object will have a greater
effect on its kinetic energy than changing its mass.
Kinetic energy = Mass x Velocity2
2
Potential Energy
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Energy that is stored and held in readiness.
An archer gives potential energy to a bow by pulling it back.
A rock poised for fall has potential energy.
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Gravitational potential energy = Weight x Height
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Different Forms of energy
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Mechanical Energy: Is the energy associated with the
motion or position of an object. (A Frog leaping through
the air. The bus you ride in.) This form of energy can
occur as kinetic or potential energy.
Thermal Energy: Total energy of the particles in a
substance or material. (Melting ice, or ice-cream
melting.)
Chemical Energy: Is potential energy stored in
chemical bonds that hold chemical compounds together.
Forms of Energy Continued
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Electrical Energy: Moving electric charges. (shock
from a metal door, batteries or power lines.)
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Electromagnetic Energy: Travels in waves.
(Ultraviolet radiation, visible light, microwaves and
infrared radiation)
Nuclear Energy: A potential energy that is stored in the
nucleus of an atom and is releases during nuclear
reactions.
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Review of Energy
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Are energy and work the
same thing?
Work and energy are not
the same thing, even
though they are measured
in the same units. Energy
is the ability to do work. As
work is done, energy is
transferred from one object
to another.
Review
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How are kinetic and potential energy
different?
Kinetic energy is the energy of motion. Potential
energy is stored energy: it has the potential to do
work.
Review
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List the forms of
energy and give an
example.
Mechanical – riding a
bicycle
Thermal – Hot water
Chemical – food energy
Electrical – batteries
Electromagnetic –
sunlight
Nuclear – fusion in a
star