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Energy
PART 2
Learning Goals for Section 2
Conservation of Energy
 Describe how energy can be transformed from one
form to another.
 Explain how the mechanical energy of a system is
the sum of the kinetic and potential energy.
 Discuss the law of conservation of energy.
Conservation of Energy
Energy Transformations,
Example #1
1. Separate a few strands of steel wool from a large
wad.
2. Hold the strands with tongs. Touch each end of
the steel wool strand to the battery terminals of a
9-V battery.
3. Write your observations of what happens.
4. Describe the energy transformations observed.
Conservation of Energy
Energy Transformations,
Example #2
1. Take a few minutes to play with the toy popper.
2. Think about the energy transformations that take
place as the toy “pops” from the table.
3. Draw a diagram of what happens as the toy pops.
Label the diagram with the different forms of
energy observed and the energy transformations
that occur.
Conservation of Energy
Energy Transformation Examples:
 light energy to chemical energy
(Photosynthesis)
 electrical energy to heat energy
(happens in light bulbs)
 Chemical energy to thermal energy to
kinetic energy (happens in car engines)
Conversions Between Kinetic and Potential
Energy
 mechanical energy = PE + KE
 Potential Energy
Kinetic Energy
 Roller coaster:
1) Energy required for ride comes from work done by the
conveyor that lifts the cars and passengers.
2) Energy from initial work is stored as GPE at the top of
the first hill.
3) Energy transformations begin: kinetic to potential to
kinetic, etc., heat energy, sound energy.
One of the tallest roller
coaster’s in the world is
the Fujiyama, in Fujiyama
Highland Park, Japan. It
spans 70 m from its
highest to lowest points.
Energy Transformations: Potential to Kinetic and
Kinetic to Potential
As a car goes down a hill on a roller
coaster, potential energy transforms
to kinetic energy.
m=515kg
PE=354kJ
KE= 0kJ
v= 0m/s
m=515kg
h=70.0m
PE= 0kJ
KE= 354kJ
v= 37.1 m/s
KE=177 kJ
PE= 177 kJ
v=26.2 m/s
KE=354
kJ
PE= 0 kJ
v=37.1
m/s
h=35.0m
At the top of this small hill, half the
kinetic energy has transformed into
potential energy. The rest of the kinetic
energy carries the car over the crest of
the hill at high speed.
The Law of Conservation of Energy
 Energy cannot be created or destroyed.
 Energy may be transformed from one form into
another.
 Energy may be transferred from one object to
another.
 The total amount of energy never changes.