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 Goes into heat, which is increased momentum of the individual Molecules within the heated object.

ENERGY KINETIC ENERGY (energy at work) KE = 1 / 2 M V 2 W = F x d POTENTIAL ENERGY (available for work) ENERGY IS THE ABILITY TO DO WORK. WORK IS THE APPLICATION OF A FORCE OVER A DISTANCE: IT IS ENERGY USED UP TOTAL ENERGY=KE + PE = CONSTANT

FORMS OF ENERGY POTENTIAL KINETIC All the rest are versions of the above HEAT (CAN BE MECHANICAL) CHEMICAL LIGHT ELECTRICAL NUCLEAR

WORK WORK IS FORCE OVER A DISTANCE NEWTON-METRE JOULE

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 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

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 CONDUCTION CONVECTION RADIATION EVAPORATION

STEPHAN-BOLTZMANN LAW E(radiation) = a constant x T 4 KIRCHHOFF’S LAW: GOOD ABSORBERS ARE ALSO GOOD EMITTERS BLACK BODY = A PERFECT EMITTER

WIEN’S LAW Lamda (max) = C/T The peak wavelength of the emitted radiation is inversely proportional to the absolute temperature

INVERSE SQUARE LAW Intensity = I o /d * * * * ** = 1/ = 1/ = 1/ = 1/ = 1/36 Radiation decreases by the square of the distance

NUCLEAR ENERGY E = MC 2 FISSION: BREAKING A NUCLEUS APART FUSION: FORCING TWO NUCEII TOGETHER

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 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 EVAPORATION CONDENSATION BOILING – HEAT OF VAPORIZATION 540 CALORIES

CHANGES OF STATE MELTING FREEZING – HEAT OF FUSION 80 CALORIES SUBLIMATION

THERMODYNAMICS HEAT FLOWING IS THERMAL ENERGY WORK CAN PRODUCE HEAT – HEAT CAN PRODUCE WORK

THERMODYNAMICS FIRST LAW: ENERGY IS CONSTANT E 1 -E 2 =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

THERMODYNAMICS FIRST LAW: TOTAL HEAT = CHANGE IN INTERNAL ENERGY + WORK OUTPUT CHANGE IN ENERGY = HEAT IN – WORK DONE

THERMODYNAMICS SECOND LAW HEAT FLOWS FROM HOT TO COOLER EFFICIENCY IS WORK/HEAT INPUT PERFECT EFF. = (T hot –T cold ) T hot

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

THERMODYNAMICS THIRD LAW: AT ABSOLUTE ZERO ALL ORDER AND MOTION CEASE