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ENERGY AND POWER. THERMODYNAMICS. 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

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energy and power

ENERGY AND POWER

THERMODYNAMICS

momentum
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.

energy
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 ENERGY=KE + PE = CONSTANT

forms of energy
FORMS OF ENERGY

POTENTIAL

KINETIC

All the rest are versions of the above

HEAT (CAN BE MECHANICAL)

CHEMICAL

LIGHT

ELECTRICAL

NUCLEAR

slide5
WORK

WORK IS FORCE OVER A DISTANCE

NEWTON-METRE

JOULE

power
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

conservation of energy
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

energy1
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

heat transfer
HEAT TRANSFER

CONDUCTION

CONVECTION

RADIATION

EVAPORATION

stephan boltzmann law
STEPHAN-BOLTZMANN LAW

E(radiation) =a constant x T4

KIRCHHOFF’S LAW: GOOD ABSORBERS ARE ALSO GOOD EMITTERS

BLACK BODY = A PERFECT EMITTER

wien s law
WIEN’S LAW

Lamda (max) = C/T

The peak wavelength

of the emitted radiation is

inversely proportional to the

absolute temperature

inverse square law
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

100

*

50

*

*

*

*

*

1

3

4

5

6

2

nuclear energy
NUCLEAR ENERGY

E = MC2

FISSION: BREAKING A NUCLEUS APART

FUSION: FORCING TWO NUCEII TOGETHER

slide14
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.
thermal expansion
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.
changes of state
CHANGES OF STATE
  • EVAPORATION
  • CONDENSATION
  • BOILING – HEAT OF VAPORIZATION

540 CALORIES

changes of state1
CHANGES OF STATE
  • MELTING
  • FREEZING –
  • HEAT OF FUSION 80 CALORIES
  • SUBLIMATION
thermodynamics
THERMODYNAMICS
  • HEAT FLOWING IS THERMAL ENERGY
  • WORK CAN PRODUCE HEAT –
  • HEAT CAN PRODUCE WORK
thermodynamics1
THERMODYNAMICS

FIRST LAW: ENERGY IS CONSTANT

E1-E2=HEAT INPUT - WORK DONE

(You can’t win)

SECOND LAW: HEAT FLOWS FROM HOT TO COOLER

(You can’t break even)

ENTROPY ALWAYS INCREASES

EVERYTHING TENDS TO GET MORE DISORDERED

(You can’t get out of the game!)

THIRD LAW: AT ABSOLUTE ZERO, ALL MOTION CEASES

thermodynamics2
THERMODYNAMICS
  • FIRST LAW:
  • TOTAL HEAT = CHANGE IN INTERNAL ENERGY + WORK OUTPUT
  • CHANGE IN ENERGY = HEAT IN – WORK DONE
thermodynamics3
THERMODYNAMICS
  • SECOND LAW
  • HEAT FLOWS FROM HOT TO COOLER
  • EFFICIENCY IS WORK/HEAT INPUT
  • PERFECT EFF. = (Thot –Tcold)

Thot

entropy
ENTROPY
  • SECOND LAW:
  • ENTROPY ALWAYS INCREASES
  • ENTROPY IS A MEASURE OF DISORDER
thermodynamics4
THERMODYNAMICS
  • THIRD LAW:
  • AT ABSOLUTE ZERO ALL ORDER AND MOTION CEASE
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