8 Momentum Momentum is conserved for all collisions as long as external forces don’t interfere.
ENERGY AND POWER THERMODYNAMICS. MOMENTUM MOMENTUM P = mv FORCE F = ma = mv/t IMPULSE Ft = mv = P...
-
Upload
dylan-fleming -
Category
Documents
-
view
220 -
download
0
Transcript of ENERGY AND POWER THERMODYNAMICS. MOMENTUM MOMENTUM P = mv FORCE F = ma = mv/t IMPULSE Ft = mv = P...
MOMENTUM
MOMENTUM P = mv
FORCE F = ma = mv/t
IMPULSE Ft = mv = P (Momentum)
MOMENTUM IS ALWAYS CONSERVEDThere has been the same amount of Momentum in the Universe since the Big Bang. Momentum lost in a collisionGoes into heat, which is increased momentum of the individualMolecules within the heated object.
ENERGY
KINETIC ENERGY (energy at work)
KE = 1/2 M V2 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
POTENTIALKINETIC
All the rest are versions of the aboveHEAT (CAN BE MECHANICAL)CHEMICALLIGHTELECTRICALNUCLEAR
POWERPOWER IS A MEASURE OF HOW FAST WORK CAN BE DONE P = W/t
POWER IS MEASURED IN WATTSWORK PER UNIT TIME
JOULES/SECONDFORCE 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 ENERGYREMAINS A CONSTANT.
ENERGY CAN NEITHER BE CREATEDNOR 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
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
Lamda (max) = C/T
The peak wavelength of the emitted radiation is
inversely proportional to the absolute temperature
INVERSE SQUARE LAW
Intensity = Io/d2
100
50
1 2 3 4 5 6
*
** * * *
1- 1002- 25 = 1/43- 11.1= 1/94- 6.25= 1/165- 4 = 1/256- 2.78 = 1/36
Radiation decreases by the square of the distance
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.
THERMODYNAMICS
FIRST LAW: ENERGY IS CONSTANTE1-E2=HEAT INPUT - WORK DONE(You can’t win)
SECOND LAW: HEAT FLOWS FROM HOT TO COOLER(You can’t break even)
ENTROPY ALWAYS INCREASESEVERYTHING 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. = (Thot –Tcold)
Thot