Transcript Potential & Kinetic Energy

Potential &
Kinetic Energy
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Alabama Course of Study
• 10.) Differentiate between potential and
kinetic energy.
• Examples:
• - potential-rock resting at the top of a hill,
• - kinetic-rock rolling down a hill
• 11.) Explain the law of conservation of energy
and its relationship to energy transformation,
including chemical to electrical, chemical to
heat, electrical to light, electrical to
mechanical, and electrical to sound.
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Energy
• Energy- ability to do work
• 2 Types of Energy
– Kinetic
– Potential
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Kinetic Energy
• Kinetic Energy- energy of an object of an
object that is due to the object’s motion
• The object has kinetic energy if it is
moving
– Kinetic energy= mv²
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– Kinetic energy increases as the mass or
velocity increases
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Kinetic Energy
• What is the kinetic energy of a car has a mass
if 1,200 kg and is moving at a speed of 20 m/s?
• KE=
• KE=
1,200 kg X (20m/s)²
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1,200 kg X 400m/s²
2
• KE=(480,000 kgXm/s²) /2
• KE=240,000 kgXm/s²
• Now do problems 1-4 on page 241
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Kinetic Energy
• A bowling ball has a mass of 20kg and it is
traveling at 2 m/s. What is it’s kinetic
energy?
• A car with a mass of 200kg travels with a
velocity of 10 m/s. What is it’s kinetic
energy?
• A skier with a mass of 15kg travels with a
velocity of 9.9m/s. What is it’s change in
velocity?
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Potential Energy
• Potential Energy- energy that an object has
because of the position, shape, or condition
of the object
• The thing on earth that affects potential
energy the most is gravity
• Height and weight after GPE the most
– Gravitational potential energy=Weight X Height
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Calculating GPE
• What is the GPE of a book with a weight of
13N at a height of 1.5m off the ground?
• GPE= Weight X Height
• GPE=13N X 1.5m
• GPE= 19.5 NXm or 19.5 J
• Now do problems 1-3 on page 242
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GPE and Weight
• A 500N skier is 40m off the ground. What is his
GPE?
• A 600N skier is 40m off the ground. What is his
GPE?
• The skier with a higher ______ has the greater
GPE.
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GPE and Height
• A 500N skier is 40m off the ground. What is
her GPE?
• A 500N skier is 60m off the ground. What is
her GPE?
• The skier with a higher _______ has the
greater GPE.
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Elastic Potential Energy
•Elastic Potential Energy- energy
associated with objects that can
be stretched or compressed
– Ex. When an archer pulls back a
bow
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Roller Coasters and Energy
What energy is at the
top of the roller
coaster?
What energy is at
the bottom of the
roller coaster?
What energy is
here?
Or here?
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Potential, Kinetic, or Both?
• Rock rolling down a hill
• Rock on the top of a hill
• You sitting in a chair
• You standing up
• A penny sinking in a cup of water
• Styrofoam ball floating in a cup of water
• Throwing a ball in the air
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Mechanical Energy
• Mechanical energy-form of energy
associated with position and motion of an
object
• ME=PE + KE
• Ex. A football has 32 J of potential energy
and 45 J of kinetic energy. What is the
ME?
• 32J + 45J= 77J
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You Teach Activity
• Green-thermal energy pg449
• Yellow- electrical energy pg 450
• Blue- chemical energy pg 450
• Pink- nuclear energy pg 450
• Orange- electromagnetic energy pg 450
• Purple-Light energy (I will provide)
• Red- sound energy (I will provide)
• White- solar energy (I will provide)
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•4-5 Posters
–No white
–Must be named
–Definition
–1 fact
–List 3 examples
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Law of Conservation of Energy
• Law of Conservation of Energy- energy
cannot be created nor destroyed but can
change from one form to another
• When energy is changed from one form to
another, it is called an energy
transfornmation
• Most forms of energy can be transformed
into other forms
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Types of Transformations
• Single Transformation- one form of energy
is changed into another one
• Ex. Cell phone transforms electrical to
electromagnetic energy
• Multiple Transformations- more than
change of form of energy
– Match-chemical energy/to thermal(heat)/
electromagnetic(light)
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Transformations between KE
and PE
• One of the most common energy
transformation is between potential
energy and kinetic energy
• Look at pendulum on page 456
– Copy picture and words
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Energy Transformations
Chemical to
Electrical
Light to Heat
Chemical to
Heat
Electrical to
Light
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More Energy Transformations
Chemical to
Electrical
Mechanical
to Sound
Electrical to
Mechanical
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