Topic 8: Energy

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Topic 8 Energy the Price We Pay

• Dr. George Lapennas
• Department of Biology

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What is Energy? Short answer Energy is the
ability to do Work.
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What is Work? Work is done when a Force acts
through a Distance in the direction of the
Force Work Force x Distance
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Are these guys doing Work?
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Is this guy doing Work?
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Now has this guy done Work?
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Power Work / Time (Force x
Distance)/Time Force x
(Distance/Time) Force x Velocity
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Power Work / Time 1 horsepower 550
foot-pounds/second
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Power Work / Time 1 horsepower 550
foot-pounds/second
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4 Fundamental forms of Energy 1 Potential
Energy (PE) 2 Kinetic Energy (KE) 3
Electro-Magnetic Energy (E-M) 4 Mass Energy
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1 Potential Energy (PE) energy of
position Energy gained by pulling something
away from an attractive force or Energy gained by
pushing something toward a repulsive force
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1 Potential Energy (PE) energy of
position Gravitational PE work done to lift
something against attraction of
gravity Gravitational PE gained weight x height
lifted mg x h
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1 Potential Energy (PE) energy of
position Elastic PE stretching a spring or a
rubber band or compressing a spring or a gas or
bending a springy bow
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1 Potential Energy (PE) energy of
position Electrical PE pulling away from
pushing toward or
toward
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1 Potential Energy (PE) energy of
position Electrical PE pulling away from
pushing toward or
toward
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1 Potential Energy (PE) energy of
position Magnetic PE
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Chemical Potential Energy
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Work done against Friction does not yield
Potential Energy
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4 Fundamental forms of Energy 2 Kinetic Energy
energy of motion
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3 Electro-Magnetic Energy light, ultraviolet,
x-rays, radio waves, micro-waves
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3 Electro-Magnetic Energy light, ultraviolet,
x-rays, radio waves, micro-waves
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3 Electro-Magnetic Energy light, ultraviolet,
x-rays, radio waves, micro-waves
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3 Electro-Magnetic Energy light, ultraviolet,
x-rays, radio waves, micro-waves
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4 Mass Energy energy derived from mass
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4 Mass Energy energy derived from mass
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4 Mass Energy energy derived from mass
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4 Mass Energy energy derived from mass
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Internal energy
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First Law of Thermodynamics Conservation of
Energy Energy can neither be created nor
destroyed The amount of Energy in an isolated
system is constant over time
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An isolated system is one where neither matter
nor energy can cross between the system and the
surroundings. The whole universe itself is an
isolated system, as there are no surroundings to
exchange matter or energy with.
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An isolated system is one where neither matter
nor energy can cross between the system and the
surroundings. The whole universe itself is an
isolated system, as there are no surroundings to
exchange matter or energy with. Energy can be
transferred (moved) from one place to
another and Transformed from one form to another
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Internal energy
The internal energy of a closed system changes
with heat transfer and work done
A closed system is one where energy can cross the
boundary, but matter cannot.
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Energy transformation from one form to another
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Energy transformation from one form to
another Pile driver
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Energy transformation from one form to
another Pile driver
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Energy transformation from one form to
another Pile driver
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Energy transformation from one form to
another Pile driver
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Energy transformation from one form to
another Pile driver
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Energy transformation from one form to another
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Energy transformation from one form to another
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Energy transformation from one form to another
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Energy transformation from one form to another
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Energy transformation from one form to another
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Energy transformation from one form to another
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Energy transformation from one form to another
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Second Law of Thermodynamics The Entropy of the
Universe can only increase (or stay the same)
over time. It cannot ever decrease. Entropy
disorder randomness
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Second Law of Thermodynamics The Entropy of the
Universe can only increase (or stay the same)
over time. It cannot ever decrease. Entropy
disorder randomness All changes that can
actually occur result in an increase in the
Entropy of the Universe Entropy is Times
Arrow which points in the direction of
spontaneous changes changes that can happen
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Entropy is Times Arrow
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Entropy is Times Arrow
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Second Law of Thermodynamics - Examples
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Temperature- a measure of the average kinetic
energy of the molecules making up a substance.
Heat- energy of molecules that is gained/lost
through a temperature difference.
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Second Law of Thermodynamics - Examples
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Second Law of Thermodynamics - Examples
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PE-KE-Elastic E-KE-PE-KE- Elastic E-KE-PE-Elastic
E
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Entropy
Every actual change results in some energy
becoming unavailable for doing work
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There are no perfect heat engines
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There are no perfect heat engines
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The End