“Physics for FUTURE LEADERS”Prof. Paul Steinhardt
PLEASE DO NOT SIT IN THE LAST 8 ROWS
Physics 115
Princeton in the Nation’s ServiceWoodrow Wilson, 1896
TAKE OUT A-B-C-D SHEETS
Simons Foundation and Princeton Gravity Initiative Program onF O R E F R O N T S O F G R A V I T A T I O N A L P H Y S I C S
p r e s e n t s
The Dawn of Gravitational Wave Astronomy
A New Window on the Universe
Beverly Berger, StanfordIntroduction by Joseph H. Taylor, Jr
P U B L I C L E C T U R ESeptember 24, 2019 | 7:00pm | McDonnell Hall A01
John GarciaFrantzesca BarronCaleb VisserGlenna GalarionAshira ShiraliMichael RamirezMenelik Graham*Hunter Sporn*Josiah Gouker*Philip SobocinskiiAatmik Gupta*Julie FangZyan WynnJake Mayer*Mark AgostinelliLaetitia DerroughReis WhiteRonnie Kihonge
0° 100°
50°
Start with equal amounts of water at 0°C and 100°C…
… combine them ...
… resulting in water at 50°.
Combination of 0th and 1st laws
TCpmQ =
heat energy
mass temperature
specific heat: the value of Cp depends on the substance.
Example:water: Cp = 1 Cal / kg oKcopper: Cp = 0.09 Cal/kg oK
Heat Capacity & Specific Heat
Which requires more energy to raise 1 degree, water or copper? A) water or B) copper or C) not enuf info
Imagine water and copper both at 50 C. Furthermore, both have the same mass m
(but different Cp)How much heat energy does the water have?
Ans: Q1 = m Cp (273 + 50 ) K.
Now suppose you have added enough heat to raise its T by 1 degree. Now how much energy does it have?
Ans. Q2 = m Cp (273+50+1) K.
How much heat did we have to add?
Q2-Q1= m Cp (1). So which requires more energy?
Did it make a difference if I used K or C?
water: Cp = 1 Cal / kg oKcopper: Cp = 0.09 Cal/kg oK
Some specific heats
Water 1 Cal/kg°C (or °K)Methyl alcohol 0.58 Cal/kg°CAluminum 0.25 Cal/kg°CMarble 0.2 Cal/kg°CGold 0.03 Cal/kg°CApples 0.87 Cal/kg°CDates 0.2 Cal/kg°CStyrofoam 0.35 Cal/kg°CCopper 0.09 Cal/kg°CIron 0.12 Cal/kg°C
If I heat up copper and iron at the same rate,which gets hotter faster?
Heat is a form of kinetic energy
…T is PROPORTIONAL TO the average kinetic energy (½mv2) of atoms and molecules.
(What does 0 oK correspond to?)
typical velocity ~ 1000 ft/sec ~ 330 m/s ~ 800 mi/hr~ speed of sound
speed of light ~ 186,000 mi/sec ~3 x 108 m/s
330 m/s is roughly the speed of what object discussed in class already?
How much heat energy is therein ordinary objects?
Each atom in a ball at room temperature is moving randomly at the speed of soundin air, about . . .1000 ft/s ~ 330 m/s ~ 800 mi/hr. This is about the same speed as a bullet.
How many Cal/gm did the bullet have?
A) .01 Cal/gm B) 1.5 Cal/gm. C) 6 Cal/gm. D) Not enough info
Suppose I throw a (very cold) baseball at 800 mi/hr.A baseball is about 150 gm.
How many Cal’s of kinetic energy have I added to the ball?A) 0.01 Cal B) 1.5 Cal C) 6 Cal D) Not Enuf Info
Suppose all that energy is converted by frictionInto heating the ball when caught in the catcher’s glove
How much will the temperature of the very cold ball increase?A)A few degrees B) 300 KC) 10000 K D) Not Enuf Info
Suppose I throw a (very cold) baseball at 1,600 mi/hr
How many Cal’s of energy have I added to the ball?A) 1.5 Cal B) 3 Cal C) 6 Cal D) Not Enuf Info
Suppose I throw a baseball at 1,600 mi/hr
If that energy were converted to heat energy,what temperature would the very cold ball reach?A) 300 K B) 600 K C) 1200 K D) Not Enuf Info
Suppose I catch the cold baseball moving at 16,000 mi/hr
If I convert that to heat energy, what is the heat energy added to the ball ?
A) 6 Cal B) 60 Cal C) 600 Cal D) 6000 Cal
Suppose I throw a baseball at 16,000 mi/hr
If I convert that to heat energy, about what is the temperature the ball ?
A) 3000 K B) 1200 K C) 12000 K D) 120000 K
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