Chapter 9 - Energy
1
Housekeeping…
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Vocabulary quizzes must be taken by Saturday.
Exam 1 begins Friday morning (perhaps
earlier…working on this one)
Exam 1 deadline: Monday 11:00 am (for a fee
later on Monday or on Tuesday)
Wednesday and Friday REVIEW.
PLEASE come to class with questions and/or
email questions to me beforehand.
Chapter 9 - Energy
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I read the chapter before
coming to class.
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Yep!
Well, more than half
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A little but not half.
None or practically
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Which statement best describes your feelings
about the upcoming exam over Unit 1?
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I’m really nervous about
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I’m
1.
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Conservation of Energy
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Total energy is conserved. But energy can and does
change forms. What forms can it have?
Two major classes: Mechanical and Internal.
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Mechanical deals with the motion and position of large objects.
Internal deals with the motion and position of atomic sized
objects.
Chapter 9 - Energy
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Types of Mechanical Energy
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Kinetic Energy = Energy from motion
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K. E. = mv2/2
A vehicle has more kinetic energy when it is more massive or
moves faster.
Chapter 9 - Energy
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(K. E. = mv2/2)
It didn’t increase
Two times
Three times
Four times
Chapter 9 - Energy
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You are walking down the sidewalk at 3 mph.
You then start running at 6 mph. By how
much did your kinetic energy increase?
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Types of Mechanical Energy
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Potential Energy = Energy from position
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Gravitational Potential Energy = mgh
(“g” is the acceleration caused by gravity)
Objects have
more GPE
when they are
more massive or
farther from the
earth.
Chapter 9 - Energy
m
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Types of Mechanical Energy
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Electrical Potential Energy =
Energy from charge separation
Objects have more
EPE when the
charge is greater and
when the separation
is greater for opposite
charges or less for
like charges
Chapter 9 - Energy
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Transformation of Energy
Gravitational Potential Energy  Kinetic Energy
A ball
tossed
in the
air
K. E.
Chapter 9 - Energy
G. P. E.
Total
Energy
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Where is the kinetic energy the
greatest in a pendulum?
Chapter 9 - Energy
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At the bottom of a
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At the top of a swing.
It is unchanging with
time
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a
1.
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Work: The Process of Transforming Energy
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Work equals
force × distance
We do work when
we go against a
force.
Chapter 9 - Energy
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Gravity
m
distance
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You must go against a force

Work is done here
but not here
Chapter 9 - Energy
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Types of Internal Energy
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Thermal: the energy of heat
Chapter 9 - Energy
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Heat Transfer
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Radiation
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The energy itself
travels through
space
Sunrise
Chapter 9 - Energy
Laser
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Heat Transfer
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Convection
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Heat material
and the
material
moves then
gives up the
heat.
Yellowstone Hot Pot
Chapter 9 - Energy
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QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Chapter 9 - Energy
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Heat Transfer

Conduction

Heat moves through the
material but the material
itself does not move or
deform.
Chapter 9 - Energy
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Heat Transfer
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Passing buckets between stationary people is like conduction.
People running back and forth with buckets is like convection.
Spraying directly from a well is like radiation.
Chapter 9 - Energy
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Types of Internal Energy
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Chemical Potential Energy: From atomic
bonding and interactions. Lots more on this
when we get to the chemistry section.
Chapter 9 - Energy
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Types of Internal Energy
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Elastic Potential Energy: From
deformations
Chapter 9 - Energy
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Types of Internal Energy
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Nuclear Potential
Energy: Very
potent because the
nuclear interaction
is so strong.
Chapter 9 - Energy
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Examples of Energy Transformation
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Bullet fired into the air
Car stopping at a stop sign
Pole vault
Making TNT
Chapter 9 - Energy
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Relativistic Energy and Mass-Energy
Equivalence
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Mass and Energy together are conserved.
Mass can turn into energy by the proportion of
the speed of light squared. That is…
E=
Chapter 9 - Energy
2
mc
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Energy can be defined as:
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A measure of destructive
capability.
The ability to exert a force
on an object while it moves
through some distance in
the direction of the applied
force.
Both 1 and 2.
None of these.
1.
2.
3.
4.
A
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increases.
decreases.
stays the same.
1.
2.
3.
Chapter 9 - Energy
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If you move two positively-charged objects
closer together, then electrical potential energy
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increases.
decreases.
stays the same.
1.
2.
3.
Chapter 9 - Energy
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If you move two oppositely-charged objects
closer together, then electrical potential energy
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Gravitational potential
energy
Kinetic energy
Internal energy
Total energy
More than one of the
above
None of the above
Chapter 9 - Energy
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As you bounce a ball, which of the following is
conserved?
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If an object has kinetic energy, then it must
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be electrically charged.
be moving.
be in an elevated
position.
be as low as possible.
be at rest
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Work is always done on an object when
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More than one force is
applied.
The object moves at a
constant speed in a straight
line.
A force moves the object
through a distance in the
direction of the force.
All of the above.
3.
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Your internal energy
decreases.
Your kinetic energy
increases.
Your gravitational potential
energy decreases.
You fall.
1.
2.
3.
4.
Chapter 9 - Energy
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If you’re skiing downhill, which of the
following must be true?
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