ENERGY AND POWER

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ENERGY AND POWER

• THERMODYNAMICS

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MOMENTUM
MOMENTUM P mv FORCE F ma
mv/t IMPULSE Ft mv P (Momentum)
MOMENTUM IS ALWAYS CONSERVED There has been the
same amount of Momentum in the Universe since
the Big Bang. Momentum lost in a collision Goes
into heat, which is increased momentum of the
individual Molecules within the heated object.
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ENERGY
ENERGY IS THE ABILITY TO DO WORK. WORK IS THE
APPLICATION OF A FORCE OVER A DISTANCE IT IS
ENERGY USED UP
KINETIC ENERGY (energy at work) KE 1/2 M V2
W F x d
POTENTIAL ENERGY (available for work)
TOTAL ENERGYKE PE CONSTANT
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FORMS OF ENERGY
POTENTIAL KINETIC All the rest are versions of
the above HEAT (CAN BE MECHANICAL) CHEMICAL LIGHT
ELECTRICAL NUCLEAR
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WORK
WORK IS FORCE OVER A DISTANCE NEWTON-METRE JOULE
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POWER
POWER IS A MEASURE OF HOW FAST WORK CAN BE DONE
P W/t
POWER IS MEASURED IN WATTS WORK PER UNIT TIME
JOULES/SECOND FORCE TIMES SPEED
(FxV) NEWTON-METER PER SECOND P W/t Fd/t Fv
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CONSERVATION OF ENERGY
ENERGY IS MANIFEST IN MANY FORMS, BUT ALTHOUGH
WE CAN CONVERT ENERGY FROM ONE FORM TO THE
OTHER, IN A CLOSED SYSTEM, THE TOTAL
ENERGY REMAINS A CONSTANT. ENERGY CAN NEITHER BE
CREATED NOR DESTROYED
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ENERGY
IF POWER IS STRENGTH, ENERGY IS ENDURANCE
ENERGY is POWER X TIME E Pt Fdt/t Fd
WORK UNIT OF ENERGY WATT-SECOND JOULE
NEWTON-METER
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HEAT TRANSFER
CONDUCTION
CONVECTION
RADIATION
EVAPORATION
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STEPHAN-BOLTZMANN LAW
E(radiation) a constant x T4
KIRCHHOFFS LAW GOOD ABSORBERS ARE ALSO GOOD
EMITTERS
BLACK BODY A PERFECT EMITTER
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WIENS LAW
Lamda (max) C/T
The peak wavelength of the emitted radiation is
inversely proportional to the absolute
temperature
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INVERSE SQUARE LAW
Radiation decreases by the square of the distance
Intensity Io/d2
1- 100 2- 25 1/4 3- 11.1 1/9 4- 6.25
1/16 5- 4 1/25 6- 2.78 1/36
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NUCLEAR ENERGY
E MC2
FISSION BREAKING A NUCLEUS APART
FUSION FORCING TWO NUCEII TOGETHER
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HEAT

• One calorie is the amount of heat to raise one
  gram of water, one degree Celsius.
• Specific Heat Each material needs a certain
  amount of heat to raise its temp one degree
  usually less than one calorie.
• One calorie is equivalent to 4.19 joules, enough
  energy to raise one gram of matter 428 metres
  higher.

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THERMAL EXPANSION

• Heat causes the atoms or molecules of any
  material to jiggle.
• When jiggling they need more room, so the volume
  increases with temperature (normally).
• Water is an exception with the temp going down
  between 4 deg and 0 degrees, water will expand,
  and on freezing will increase volume by 9.
• Ice has a density of 0.92 thus it floats.
• The lowest levels of a pond freeze last, if at
  all.

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CHANGES OF STATE

• EVAPORATION
• CONDENSATION
• BOILING HEAT OF VAPORIZATION
• 540 CALORIES

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CHANGES OF STATE

• MELTING
• FREEZING
• HEAT OF FUSION 80 CALORIES
• SUBLIMATION

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THERMODYNAMICS

• HEAT FLOWING IS THERMAL ENERGY
• WORK CAN PRODUCE HEAT
• HEAT CAN PRODUCE WORK

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THERMODYNAMICS
FIRST LAW ENERGY IS CONSTANT E1-E2HEAT INPUT -
WORK DONE (You cant win)
SECOND LAW HEAT FLOWS FROM HOT TO COOLER (You
cant break even)
ENTROPY ALWAYS INCREASES EVERYTHING TENDS TO GET
MORE DISORDERED (You cant get out of the game!)
THIRD LAW AT ABSOLUTE ZERO, ALL MOTION CEASES
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THERMODYNAMICS

• FIRST LAW
• TOTAL HEAT CHANGE IN INTERNAL ENERGY WORK
  OUTPUT
• CHANGE IN ENERGY HEAT IN WORK DONE

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THERMODYNAMICS

• SECOND LAW
• HEAT FLOWS FROM HOT TO COOLER
• EFFICIENCY IS WORK/HEAT INPUT
• PERFECT EFF. (Thot Tcold)
• Thot

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ENTROPY

• SECOND LAW
• ENTROPY ALWAYS INCREASES
• ENTROPY IS A MEASURE OF DISORDER

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THERMODYNAMICS

• THIRD LAW
• AT ABSOLUTE ZERO ALL ORDER AND MOTION CEASE