NOTES
FROM PffP MIDTERM REVIEW SESSION 2/21/09
Chapter 1
l batteries
l Explosives (TNT)
l chocolate chip cookies, butter (food)
l fossil fuels (coal < gasoline < natural
gas)
l hydrogen
l moving objects (depends how fast/ how heavy 
smart rocks/brilliant pebbles)
l uranium
* Energy = the
ability to do work = force applied over a distance
l kinetic (motion)
l gravitational potential (height)
l mechanical (work)
l electrical (lightbulb, circuit)
l thermal (heat)
l chemical (bonds between molecules)
l Nuclear (bonds between atomic nucleii)
Formula for
Kinetic Energy: E = ½ mv²
A. list from I.
is roughly in order by energy density
B.
COST: coal < natural gas < gasoline < electricity <
car battery < computer battery << AAA battery.

light bulb brightness depends on power, but
isn't the same thing

home lighting = 1 horse(power) = 1kW

humans can generate 1hp briefly, 1/7 hp
sustained

1
can of coke = 1/2 hr of vigorous exercise

Gasoline 
Hybrid 
Hydrogen Fuel cell 
Solar Power 
Pros 
high energy density, convenient to transport & store, no residue from burning, was relatively cheap 
allows gas engine to operate more efficiently, uses energy from braking 
even more energy density than gasoline (3x more energy /gram) waste = water 
renewable source 
Cons 
expensive compared to coal, contributes to atmospheric CO2 
batteries are expensive to replace ($100 / lb) 
dangerous to store, difficult to transport (3x less energy per gallon) takes up lots of space, "made" not mined. 
not enough space on car rooftop to generate 50400 hp, only available during day, solar cells are expensive. 
best use 
cars (then) 
cars (now) 
bus, trucks, airplanes 
boats, planes? power plants* 
*Other forms of generating electricity:
WIND, COAL, NATURAL GAS
Chapter 2
I. Heat is the average
kinetic energy of atoms or molecules in a substance
A. Heat energy = random motion of atoms.
B. Brownian motion was the first
proof of the atom's existence.
C. The speed of molecules in air = speed
of sound ~ 1000 ft/s
Remember:
speed of light = 1ft/computer cycle (ns)
D. Hiss/snow on radio/TV is random
electron movement
E. When energy of nonrandom motion is
turned into heat, the energy of the molecules is going from ordered to disordered (Columbia Space shuttle) (Mach rule: T =
300M^2)
II. Temperature is a way of measuring the
random KE of molecules
A. Remember: Lighter
molecules move faster than heavier ones as the same temp.
B. 3 different
scales of temperature  Celsius, Fahrenheit, Kelvin.
Remember:
1 deg. C ~ 2 deg. F
III. 0th Law of Thermodynamics
A. Objects in thermal contact will
eventually come to the same temperature (ex. hydrogen, cold death of the
universe)
IV. Thermal expansion happens differently
in different materials
A. Cooling contracts, heating expands,
Water (at freezing) is the only exception
Remember:
1C rise in temp makes things expand between 1/1000 and 1/100,000
B. Examples: thermometer, levees, tight
lids, shattering glass, rise in sea level
Remember:
predicted sea level rise 6in  3ft
V.
Thermal expansion in air gives us air pressure,
air is a poor conductor
A. P = constant x Temperature
B. examples: hot
air balloons, hurricanes, airbags, leidenfrost.
VI. Heat can be used as a source of energy
(in order to do useful things)
A. Engines/ explosions
1. All engines are inefficient (Gas
25%, Coal 33%, Electricity 90100%)
2. Greater temperature difference yields greater
efficiency (VW Bug).
B. Refrigerators / Heat pumps
1.
They're the reverse of an engine  they use mechanical energy to create a
temperature difference. (They expand & cool a gas, which can then cool other
things, or take heat from cool air and pump it elsewhere).
2. Running a heat pump is more effective
(NOT efficient) than burning fuel.
VII. Heat flows by conduction, convection,
and radiation
A. Different materials conduct heat at
different rates  conductors vs. insulators
VIII. The Three Laws of Thermodynamics:
0) Objects in
contact reach the same temperature
1) Energy is Conserved
2) You can't extract
heat energy without a temperature difference / entropy will always increase
3) Nothing can reach
absolute zero (where entropy = 0)
Chapter 3
Ben Geller
February, 2009
U.C. Berkeley – Physics C10
Chapter 3 Review Notes: Force, Space and Gravity
The role of forces in classical (pre20th century) physics
is determined entirely by 3 very simple laws developed by Isaac Newton (this is
what makes physics what it is:
huge numbers of phenomena are explained with a small set of simple
laws). NewtonÕs 1st Law states
that objects will move in a straight line at a constant speed unless acted on
by an external force. We live in a
world with lots of friction, so this first law is less obvious than it would
otherwise be. If you push a book
across your desk, it doesnÕt keep moving at a constant speed. It stops! It stops not because Isaac Newton is wrong, but because it
was indeed acted on by an external force: friction. Push that same book in outer space, where there is neither
friction nor air resistance, and it will indeed continue in a straight line at
constant speed forever.
What does this first law say about objects moving in a
circle at a constant speed? This
is a pretty important question, since satellites and the moon and the earth
itself seem to be doing just that.
By NewtonÕs 1st Law, there must be a force on the object that is moving
it in a circle (otherwise it would just travel in a straight line, not in a
circular path). It turns out that
the force that causes an object to travel in a circle at constant speed must be
directed toward the center of the circle (this can be proved with a combination
of geometry and NewtonÕs 2nd Law, but letÕs not bother proving it – itÕs
true).
NewtonÕs 2nd Law states that the force applied to an object
causes the object to accelerate at a rate this is determined by the equation F
= ma, where a is the acceleration that results from the force F, and m is the
ratio between the force applied and the acceleration that results. We call that ratio the objectÕs
mass. If an equal force is applied
to two objects of differing mass, the more massive object will accelerate at a
slower rate than the more massive one.
ThatÕs NewtonÕs famous 2nd Law. (In the 20th century it was shown that Newton 2nd Law
is only right if the objects under consideration are moving much slower than
the speed of light, but that is a discussion that weÕll put off for a couple of
months!)
If an object is not accelerating (that is, if itÕs moving in
a straight line at constant speed, or not moving at all), then NewtonÕs 2nd Law
tells us that there must be no NET force on the object. This does not necessarily mean that
there are no forces at all acting on the object, just that whatever forces are
acting balance each other out exactly.
Consider a boat floating on the ocean or a person floating on the
surface of a swimming pool: in
both case, the objectÕs downward weight (the pull of gravity) is exactly
balanced by an upward force
(called buoyancy) that keeps you or the boat from sinking. The buoyant force, it turns out, is
always equal to the weight of the fluid that you or the boat displaced. If the weight of the fluid displaced by
an object is more than the weight of the object itself (as in the case of, say,
a helium balloon), then the object rises until the weight of the outside fluid
matches its own weight (the ÒfluidÓ in this case would be the air outside of
the balloon, which gets less and less dense at higher altitudes). If the object is heavier than the fluid
it displaces, the object sinks (like a rock in a swimming pool or a human in
foamy water).
In the case of the object that is moving in a circle at
constant speed, the acceleration, like the force, must be directed toward the
center of the circle. By geometry,
one can show (come see me if youÕre curious!) that the value of this
acceleration is given by v^2/r, where v is the objectÕs speed and r is the
radius of the circle in which it travels.
The object is always accelerating toward the center of the circle at
this v^2/r rate, but it never gets closer to the center because of its
tangential motion. The force that
causes this acceleration toward the center must, according to NewtonÕs 2nd Law,
be given by F = ma = mv^2/r. But
what force is it that is causing the object to travel in a circle? What force is causing this v^2/r
acceleration?
It could be any number of things. Perhaps the object is attached to a rope that is being swung
around – in that case it is the tension in the rope that is providing the
force. Perhaps the object is you,
and you are on the Òrotor,Ó a famous (and, I can attest, nauseating) amusement
park ride in which one places their back against a wall and is spun in a circle
so fast that the ground can fall away beneath oneÕs feet – in that case
it is the wall of the ride pushing on your back that is causing you to
accelerate toward the center at v^2/r.
Anyone who has worked in a biology lab knows that one of the
most ubiquitous and useful instruments in biology is the centrifuge. Test tubes are placed in the centrifuge
and spun around at very high circular velocities. Because the force on each component of the sample in the
tube is given by F = mv^2/r, components of the sample having more mass feel
more force than those having less mass.
This results in a spatial separation between the heavier and lighter
components in the sample, a very useful result when working with cells. (This technology is also
important for the separation of uranium isotopes, as weÕll see in a couple of
weeks when discussing nuclear technology.)
Another force that can cause circular motion is
gravity. The force of gravity
between any two objects having mass is proportional to the product of the two
masses and inversely proportional to the square of the distance between
them: F = GMm/r^2. Here, M and m are the two masses and r
is the distance between them. G is
just a constant that makes the units easy to manipulate – itÕs not
important for our purposes. If m
is an object near the surface of the earth, and M is the earth itself, then r
is the radius of the earth and the force felt by object m is F = ma = m(GMearth/rearth2).
The numbers in parentheses comprise the object mÕs acceleration near the
surface of the earth, and are easy to look up online – try it and you
will find that the ratio GMearth/rearth2 is equal to 10 meters per second per
second, or, equivalently, 22 miles per hour per second. This is why objects dropped near the
surface of the earth fall toward the earth at 22 miles per second per
second. After 1 second of freefall
you are going at 22 mph, after 2 you are going at 44 mph, etc. That magic number of 10 meters
per second per second that you may have heard about in high school is just a
special case of the more general gravitational law, useful when you are near
the surface of the earth (as we often are!) but by no means a general law of gravity
anywhere else. You would fall much
more slowly than 10 meters per second per second near the moon, and much more
quickly near Jupiter.
Each mass in this gravitational force equation feels the
same force. This is due to
NewtonÕs 3rd and final Law, which states that if object A exerts a force on
object B, then object B exerts the same force (though in the opposite
direction) on object A. So when
two masses interact, they pull on each other equally hard, i.e., they both feel
the same amount of gravitational pull.
NewtonÕs 3rd Law says that the earth pulls on the sun just
as hard as the sun pulls on the earth.
Why then does the earth go around the sun as opposed to the sun going
around the earth? When you drop
your pencil, the pencil pulls on the earth just as hard as the earth pulls on
the pencil. Why then does the
pencil fall to the earth as opposed to the earth rising to meet the
pencil? The answer in both cases
is that, although the forces are equal, the accelerations are not. Remember, if an equal force is applied
to two objects that differ in mass, the less massive object accelerates more
than does the more massive one.
The sun is much more massive than the earth, and the earth is much more
massive than the pencil! The 3rd
Law also explains plane travel (the plane pushes down on the air around it, but
the air pushes back just as hard, and in the upward direction) and rocket
propulsion (the rocket pushes the fuel out its rear, and the fuel pushes the
rocket up into space). These
processes are sometimes described in your textbook in terms of momentum
conservation, but you can also think of them in terms of NewtonÕs 3rd Law
– you should understand both ways of thinking about it!
We now know enough to do a couple of interesting and
practical calculations. First
letÕs figure out how fast Low Earth Orbit satellites need to be going if they
are to remain in orbit just above the earthÕs surface. These satellites are going in a
circular path, so they are accelerating toward the center of that circle at a
rate of a = v^2/r. The force that
is causing that acceleration is gravity, which we now know is given by F =
GMm/r^2. Putting these two facts
together with NewtonÕs 2nd Law (F = ma), we arrive at the following equation
for objects that are orbiting the earth:
(GMm/r^2) = m(v^2/r).
This may look complicated, but remember that this is just F
= ma, where a = v^2/r and F is the gravitational force! Remember that M is the mass of the
earth and, for satellites that are just a hundred or so miles above the earth, r is roughly equal to the radius of the earth. Putting these values in and solving for
v, we find that the LEO satellites must travel at about 5 miles per
second. This is where that rather
arbitrary number discussed in lecture comes fromÉ at 5 miles per second, the
LEO satellites accelerates toward the center of the earth at a rate of v^2/r
but never gets closer to the center!
For geosynchronous orbit, one would have to repeat this
calculation with the constraint that the satelliteÕs orbit must take precisely
24 hours. If one does that, one
finds that the r value which satisfied the above
equation is about 26,000 miles, or 22,000 miles above the earthÕs surface. That is the height at which a
satelliteÕs orbit is geosynchronous.
Finally, letÕs figure out why there is lots of oxygen and
nitrogen in the earthÕs atmosphere, but very little hydrogen. This is a very nice calculation to end
with, since it combines ideas from each of the first three chapters of the
course. To do this, we need
to consider a concept called Ôescape velocityÕ. If instead of just sending a satellite into orbit, we wanted
to actually send it far into outer space (i.e., if we wanted the satellite to
escape the earthÕs pull entirely), then we would need to provide it with more
velocity than is required by the 5 mile per second orbit speed rule. For reasons that I wonÕt go into here
(but am happy to go into elsewhere if you are interested!), we would actually
need to provide such a satellite with exactly twice the speed that it would
need just to be in orbit. We need
to give objects a speed of about 10 miles per second if they are to escape the
earthÕs gravitational pull and drift off into space – this is the Ôescape
velocityÕ.
What on earth does this have to do with the lack of hydrogen
in the earthÕs atmosphere? Well,
you should recall from the previous chapters that at the temperature of the
earthÕs atmosphere, all the molecules are moving around with the same kinetic
energy (things at the same temperature have the same kinetic energy). This does not mean, however, that all
molecules have the same speed.
Since kinetic energy is given by KE = ½ m v^2, lighter molecules
(smaller m) will have larger speeds (bigger v) and heavier molecules (bigger m)
will have smaller speeds (smaller v).
At the temperature of the earthÕs atmosphere, hydrogen, nitrogen and
oxygen molecules all have the same kinetic energy, but they have very different
speeds. Oxygen and nitrogen
molecules, being much heavier than hydrogen molecules, are moving around
relatively slowly. Hydrogen
molecules are moving around very fast, so fast in fact that they often exceed
10 miles per second! What happens
when an objectÕs speed exceeds this 10 miles per second escape velocity? The object flies off into space, never
to return. Most of the hydrogen
has escaped the earth in this manner, leaving the slower moving nitrogen and
oxygen molecules behind.
Conversely, there is a LOT of hydrogen at the sun, since it is unable to
escape the sunÕs much stronger gravitational pull.
Chapters 4 & 5
Radiation Poisoning 
Cancer 
Radiation damages cells, disrupts bodily processes 
Radiation damages DNA such that cells stop regulating their own growth 
Symptoms include nausea, listlessness, loss of hair, death 
Symptoms include cancer 
Effects at 100 rem, LD50 at 300 rem 
2500 rem = 1 cancer 
Linear hypothesis – draw graph for
linear effect
Linear Hypothesis 
Threshold hypothesis 
Says that the linear effect is true even at very low doses of radiation 
Says that below a certain level of radiation, there is no additional risk of cancer 
Better safe than sorry! 
The body can repair a little bit of damage no problem. 
ItÕs difficult to test these hypotheses since about 20% of people will get cancer anyway. Human testing is frowned upon. 
Radioactive dating
Radiocarbon dating 
Potassiumargon dating 
C14 is made in the atomosphere, plants breathe it in, animals eat plants, so all living things have a certain level of C14 while theyÕre alive. 
K40 is leftover from the formation of the solar system, and is found in rocks (and people) 
When an organism dies, C14 decays, but isnÕt replaced, so the amount of C14 decreases over time. The longer its been dead, the less C14 
K40 in rocks decays, turns into argon gas which is trapped in the solid rock. The longer the rock has been solid, the more argon gas it will have trapped. 
Only works on things that died within the last 60,000 years. 
Most useful for rocks at least 100,000 years old 

Uranium
bombs 
Plutonium
bombs 
Hydrogen
bombs 
Fuel 
U235 
Pu239 
Pu239, H_{2}, U238 
Design 
Guntype 
Implosion 
Thermonuclear 
Advantages 
Easy to build 
Easy to get plutonium 
Really frigginÕ powerful 
Disadvantages 
Hard to purify U235 (from 0.7% to 80%) 
Hard to build implosion mechanism 
You still need a fission bomb (uranium or plutonium) 
Historical role 
Hiroshima (ÒLittle BoyÓ) 
Nagasaki (ÒFat ManÓ) 
Most of our current arsenal of ~12,500 nuclear weapons 
How is nuclear power different?
á
Lower
power – boil water, turn turbine, generate electricity
á
Sustained
chain reaction – no doubling
o On average, only 1 of 2 neutrons hits
another U235
á
Requires
only 3% U235, not 80%
á
Uses
a moderator (water, heavy water, graphite)
o slows down neutrons (thermal neutrons)
o thermal neutrons more easily absorbed by U235
o Also keeps reactor cool
á
Produces
Pu239 when other neutron hits U238
o Breeder reactor – use Pu239 as
fuel, extra neutrons hit U238
¤
doubles amount of Pu239 in 10 years
á
WonÕt
blow up like a nuclear weapon
o Slow neutrons means slower chain reaction
á
Can have a ÒmeltdownÓ if moderator disappears
o chain reaction stops
o temperature increases, material melts
Three Mile Island vs. Chernobyl
Three Mile Island 
Chernobyl 
Pennsylvania 
Ukraine (USSR) 
Meltdown 
Reactivity accident 
Moderator pumps fail 1/3 of core melts, but not through
floor 
Chain reaction increases out of control Water coolant boiled rapidly 
explosion Carbon moderator set on fire Radioactive material escapes in form of
smoke 
Nobody hurt 
~30 deaths from radiation illness ~4,000 cancer deaths expected 