*Updated: *30 April 2013 Tuesday*.*

Reminder that ICES Student Course Evaluations are available now online via GoWMU .

Monday 4/15: **How does q _{1} know that q_{2} is there?**
-- "Action at a Distance" -- Gravity and the Electric Force are not
contact forces. The mathematical construct of the Electric Field. E is not an
observable quantity. (Side example: Methods of measuring speed v, do not
directly measure speed v.) Electric Fields, E = k q / r² (E-field from one
point charge) and F

- Benjamin Franklin invented the lightning rod -- a series of metal spikes on
the roof of a building, connected by metal conducting paths to channel the
moving charges (current) from a lightning strike away from the roof. Please
note that the spacing and maintenance of lightning rods needs to be done by
qualified professionals. Space them too close together or too far apart and the
lightning will hit
*between*the lightning rods, guaranteeing that the roof will burn down!

Tuesday 4/16: ** The Simplest Circuit: Battery, wires, load
(resistor). Conductors** (metals) versus non-conductors (

- Technically the wires in a circuit also have a resistance and they too can get hot due to Joule heating. However, for our purposes, we'll treat the wires as perfect conductors, R = 0. There ARE superconductors, materials which below a critical temperature really do have perfect conductivity and zero resistance. None of them currently work at room temperature, however.
- NOTE ABOUT Pre-Final Grades: I had to CORRECT the data from what was first posted -- for most people, their letter grades either stayed the same or went up. If you looked at the posted grades on Monday 4/15 or early Tuesday 4/16, please check again. If you came to Dr. Phil's office or we exchanged grade info on emails between Fri 4/12 and Mon 4/15, get in touch with me again.
- Remember, if you're using the Testing Center for your Final Exam, reserve your time and send Dr. Phil an email. You may not be able to get the same day/time as the regular Final Exam.
**Additional Problems 8-11.**(Click here for a copy.)

Wednesday 4/17: **The Simplest Circuit:** Battery, wires, load
(resistor). Series and Parallel Resistors. Two
devices connected together in a circuit can only be connected two ways: series
or parallel. In Series, same current, share voltage. Equivalent resistance is
always larger. In Parallel, same voltage, share current. Equivalent resistance
is always smaller. **Resistor Network Reduction.** The battery only
"sees" an equivalent resistor, which controls its current. So we
could (but won't) reduce a resistor network to a single equivalent resistance,
go back and fill in the table for V = I R and then P = I V. In the example
sketched in class, Resistor R_{1} sees the largest current and
dissipates the largest amount of energy per second (Power in Watts). This means
it is also the most vulnerable. Story of radio "repair" call from
4,000,000,000 miles. **Electricity and Magnetism Together Can Create Light.
**The Great 19th Century Debate: **Is Light a Particle or a Wave**?
(Wave-Particle Duality did not seem obvious at the time. Later on, deBroglie
showed that even matter has both a wave and a particle nature.) Q13 Take-Home
on Simple Circuits and Resistors, due on Friday 19 April 2013. (Click
here for a copy.)

- Video: Standing waves and resonance can occur when you don't want them to,
sometimes with disasterous results. See
The
Tacoma-Narrows Bridge Disaster.
*NOTE: The video in this article is shown in real time -- it is NOT speeded up.*

Thursday 4/18:

Friday 4/19:

Monday 1/7: Class begins. The nature of studying Physics. Science education in the United States. Natural Philosophy. The Circle of Physics. "Speed Limit 70" First Equation: Speed = Distance / Time. In terms of variables, a classic three-variable equation: v = d / t .

- Quiz 1 will be in-class on Friday 11 January 2013. Part I will be some attendance paperwork. Part II will be on our equation v = d / t. (This will be our only non-Metric System quiz.)

Tuesday 1/8: To understand the underlying concepts we need to Simplify The Universe. Aristotle and the Greek Philosophers. Observation vs. Experiment - Dropping the book and the piece of paper (2 views). Theory and Measurement.

- The Apollo 15 Hammer and Falcon Feather Drop webpage. QuickTime movie: (low res 8MB, higher res 80MB)
- Reminder to those of you who need take the lab -- PHYS-1080 is a separate 1-credit course. Labs start next week.

Wednesday 1/9: First Equation: Speed = Distance / Time. v = d/t .
Development of Speed equation for Constant or Average Speed. delta-x = ´x
= x_{final} - x_{initial} = x_{f} - x_{i} , x =
x_{0} + v t . Discussion of formula cards. Distribute
Syllabus.

Thursday 1/10: Speed. 60 m.p.h. = "A Mile A Minute". It's a nice
alliterative phrase and wasn't possible for Man to move at 60 mph until 1848:
The Antelope,
but it really isn't a special speed, just an accident of the English system of
measurement. English system of measurement. SI Metric System.
Prefixes. What do we mean by Measurements?
"Units will save your life." What is "1 m/s"? We need a few
benchmark values to compare English and SI Metric quantities. *NOTE:
English-to-Metric conversions will NOT, with two exceptions, be tested on in
this course. *60 m.p.h. = 26.8 m/s. 1.00 m/s = slow walking speed. 10.0 m/s
= World Class sprint speed (The 100 meter dash --
Usain Bolt is the current
Olympic (9.683 seconds) and World (9.58 seconds) record holder.) 26.8 m/s = 60
m.p.h.. 344 m/s = Speed of sound at room temperature. 8000 m/s = low Earth
orbital speed. 11,300 m/s = Earth escape velocity. 300,000,000 m/s = speed of
light in vacuum (maximum possible speed).

Friday 1/11: Topic 1 assigned. (Updated Searchable booklist available online here .) Quiz 1 In-Class.

- If you missed class, you will be able to get some of the points by downloading Quiz 1A from the website and turning it in. (Click here for a copy.)

Monday 1/14: **The P-O-R (Press-On-Regardless)** road rally problem.
"You can't average averages." Comments on Q1½ -- solution
already posted on class webpage. Note that part (c) is just like the P-O-R
problem. **A simplified trip to the store** --
The S-Shaped Curve.
Acceleration. Physics
Misconceptions: Things you think you know, are sure you know, or just assume to
be true in the back of your mind... but aren't true. Aristotle was sure that
heavier objects always fell faster than lighter objects, but we did a
demostration on Tuesday which showed that wasn't always true. Example: You're
driving a car. To speed up, you need to put your foot on the accelerator (gas
pedal), so YES, you are accelerating -- True. To drive at a constant speed, you
must still have your foot on the accelerator, so YES, you are accelerating --
Not True because constant v means a = 0. To slow down, you must take your foot
off the accelerator and put it on the brake pedal, so NO, you are not
accelerating -- Not True because v is changing, so a < 0 (negative).
Just as the equation *v = d / t* is for constant or average speed, the
equation *a = delta-v / delta-t* is for constant or average acceleration.
Finding the set of Kinematic Equations for
Constant Acceleration.

- Physics Help Room starting up today -- 2210 Rood I think is the new room number -- converted from one of the labs on the 2nd floor.

Tuesday 1/15: **PTPBIP - Putting The Physics Back Into The Problem**.
Handout on (1) Prefixes for moving the decimal place for larger and smaller
powers of ten in the SI metric system, (2) Scientific Notation, as in 1.23
× 10^{12} and using the "EE" key on your calculator, and
(3) **Dr. Phil's Simplified Significant Figures** for multiplication,
division and trig functions. (Click here if you
need a copy.) Finding the set of Kinematic
Equations for Constant Acceleration. The Equation Without Time -- Avoiding
the Quadradic Formula. To aid in setting up problems with the kinematic
equations, you might try to list all six kinematic variables (x_{0}, x,
v_{0}, v, a and t) and give the values for those you know, those you
don't know and those you want to find out. This will help you choose which
kinematic equation(s) you'll need. **What do we mean by a = 1 meter/sec²
?** You cannot accelerate at 1 m/s² for very long. Types of Motion: No
Motion (v=0, a=0), Uniform Motion (v=constant, a=0), Constant Acceleration
(a=constant). We generally cannot accelerate for very long.

Wednesday 1/16: Return Q1½. Finish car acceleration problem from
yesterday -- *t = 19.03 sec. ***Problem**: A rifle bullet is fired from
rest to faster than the speed of sound, 415 m/s, in a distance of 1.00 m. Find
*a*. Answer, *a = 86,110 m/s²*. This is huge, which is why we
don't fire people out of rifle barrels. Find *t = 0.004819sec*. Again, we
could solve for *t* using two different equations, but will still get the
same result because there is one Physics. To aid in setting up problems with
the kinematic equations, you might try to list all six kinematic variables
(x_{0}, x, v_{0}, v, a and t) and give the values for those you
know, those you don't know and those you want to find out. This will help you
choose which kinematic equation(s) you'll need. **Free-Fall:** If we ignore
air resistance, all objects near the surface of the Earth fall towards the
Earth at the same rate. *a _{y} = -g* ;

- Table of a = 1.00 m/s² :

t (seconds) |
v = a t (m/sec) |
x = ½ a t² (meters) |

0 |
0 |
0 |

1.00 |
1.00 |
0.500 |

2.00 |
2.00 |
2.00 |

3.00 |
3.00 |
4.50 |

4.00 |
4.00 |
8.00 |

5.00 |
5.00 |
12.5 |

10.0 |
10.0 |
50.0 |

25.0 |
25.0 |
312.5 |

Thursday 1/17: **Prepping for 2-D Motion:** We can look at motion in
1-dimension in different directions. We usually use *x* in the horizontal.
*y *can either be another horizontal dimension or in the vertical. We can
rewrite the Kinematic Equations for constant acceleration for *x* or
*y*. It turns out that if *x* and *y* are perpendicular to each
other, then they are independent, so we will be able to break down 2-D motion
into two 1-D motion problems. **Free-Fall:** If we ignore air resistance,
all objects near the surface of the Earth fall towards the Earth at the same
rate. *a _{y} = -g* ;

- When I updated yesterday, I failed to put the links up for the story of Scott Crossfield and the explosion of the X-15 -- you should scroll up to yesterday's bullet points and check it out.
- Back on the class web page, I started putting Sample Exam 1s -- some have solutions, some do not. The ones without solutions you need to figure out by PTPBIP or comparing answers with others to see if you're right. After all, you don't have the answers in front of you when you take the exams for real.
- FORMAT FOR EXAM 1: Problem 1 -- ten multiple guess questions very much like those you'll see in the Sample Exam 1s. The first group will use the handy little table for Number of Minutes per Mile at various speeds in mph. Problem 2 -- one problem with five parts, much like those in the Quizzes and like the problems in the Sample Exams 1s.

Friday 1/18: Quiz 2 in-class.

- Remember, no classes on Monday due to MLK Day Activities.

Monday 1/21: **MLK Day to Honor Dr. Martin Luther King, Jr. **-- Classes
Do Not Meet at WMU -- University-wide activities.

Tuesday 1/22: **The consequences of Falling Down... ...and Falling Up**.
The Turning Point ( v_{y} = 0, but a_{y} = -g during whole
flight). The illusion of "hanging up there in the air" at the
turning point. **Motion in
Two-Dimensions:** You may be able to break it down into two one-dimensional
problems, connected by time, which you can already solve. **Example**: The
guy with the fedora and the cigar. There are 6 variables from the first
dimension (x_{0}, x, v_{0x}, v_{x}, a_{x}, t),
but only 5 from the second (y_{0}, y, v_{0y}, v_{y},
a_{y}), because time is the same. Remarkably, with a couple of
reasonable assumptions, there are only 3 unknown variables (v_{0x}, t,
v_{y}). Time links the two one-dimensional problems together. We need
to find v_{0x} , but we don't know the time. So we can find the time it
takes to fall from the top of the building in the *y*-problem, then use
that in the *x*-problem.

*A slice of Pi at ConFusion 2013.* (Click on photo for larger.)
©2013 Dr. Philip Edward Kaldon (All Rights Reserved)

Wednesday 1/23: Another problem solved by using two linked 1-D problems:
**Classic Simple Pursuit** (Cop and the Speeder). Starting from rest, the
contant accelerating cop ends up with a final speed twice that of the uniform
motion speeder -- because they both have to have the same average speed (same
place, same time). There are two times when they are in the same place and the
same time -- the other solution is at t=0. **Two kinds of numbers:** Scalars
(magnitude and units) and Vectors (magnitude, units and direction). Compass
directions (N, S, E, W, NE, SE, SW, NW).

Thursday 1/24: (Apologies for being late to class due to excessive number of accidents on the icy roads.) Return Q2. Demo these class web pages. Look at Sample Exam 1s. Discuss how to use the mph and sec/mile chart seen in the multiple-guess problems.

- NOTE: If on any one part (a-e) of Q2 you lost 4000-6000 points, please return your Q2 to Dr. Phil -- I want to check the grading.

*2nd and 4th wrecks of the day -- drive careful out there!* (Click on
photos for larger.)

Friday 1/25: Quiz 3 in-class.

- If you are using the Testing Center for Exam 1, you must (a) make an appointment at the Testing Center AND (b) send me an e-mail saying that you are taking your Exam 1 at the Testing Center at such-and-such a time, so that I know to send an exam over there.
- Originally I was going to hand out a take-home Quiz 4 on Friday, but with Thursday's shortened class, we'll hand it out next week.

Monday 1/28: **Two kinds of numbers:** Scalars (magnitude and units) and
Vectors (magnitude, units and direction). Adding and subtracting vectors:
Graphical method. To generate an
analytical method, we first need to look at some Trigonometry.
Right Triangles: Sum of the interior angles of
any triangle is 180°, Pythagorean Theorem (a² + b² = c²).
**Standard Angle** (start at positive *x*-axis and go
counterclockwise). **Standard Form:** 5.00m @ 30°. **Practical
Trigonometry**. S`OH`C`AH`T`OA`. **Adding and
subtracting vectors:** Analytical
method. (Check to make sure your calculator is set for Degrees mode. Try
cos 45° = sin 45° = 0.7071) Why arctangent is a stupid function on
your calculator. **Examples**: vector C = vector A + vector B, vector D =
vector A - vector B. Dr. Phil's Method uses a table you fill out with the x-
and y-components, to allow you to easily add or subtract the columns. Then use
your sketch to check your work. Q4 Take-Home on Vector Addition, due on
Wednesday 30 January 2013.

Tuesday 1/29: Finishing vector problems: (1) **Examples**: vector C =
vector A + vector B. (For studying, you might try to find vector D = vector A -
vector B). (2) Finding final velocity of problem with the guy with the fedora
and the cigar in Standard Form. **Ballistic or Projectile Motion** 2-D
problem where a_{x} = 0 and a_{y} = -g. Covers anything shot,
thrown or kicked into the air which is unpowered and where we can ignore air
resistance. Ancient cannons. We can always use the Kinematic Equations, but we
can also derive specialized equations: Max Height, h = v_{0}²
sin² ¸ / 2 g .

- With vectors, we have officially closed the book on material for Exam 1. If you run across a problem in the Sample Exam 1s that you don't know what it means, it might be something we haven't covered yet! (grin) The material we started today on Ballistic/Projectile motion is based on the kinematic equations for constant acceleration and vectors, things that we have covered. However, the specialty equations we are developing are NOT part of Exam 1.
- Q4 is "due Wednesday". You can turn it in at class, turn it in during Office Hours to me, or turn it in at the beginning of class on Thursday if you need to -- please don't do Q4 during our class or skip class because it isn't done.

Wednesday 1/30: Return Q3. **Ballistic or Projectile Motion** 2-D problem
where a_{x} = 0 and a_{y} = -g. Covers anything shot, thrown or
kicked into the air which is unpowered and where we can ignore air resistance.
Ancient cannons. We can always use the Kinematic Equations, but we can also
derive specialized equations: Max Height, Time to Max Height, Range Equation.
Two Dangerous Equations. You can only use
the Range Equation if the Launch Height = Landing Height. But the sin (2
θ) term in the Range Equation means that (1) 45° gives the maximum
range for a given initial velocity and (2) that all other angles have a
complementary angle (90° - θ) that gives the same range (but a
different time and height). High and low trajectories for Range Equation.

Thursday 1/31: WMU Closed Today -- Classes Canceled.

- Western Michigan University is closed and all classes and public events are canceled today, Jan. 31, due to severe winter weather. The closure includes the University's main campus in Kalamazoo as well as regional locations in Grand Rapids and Battle Creek.

Friday 2/1: Exam 1 MOVED to TUESDAY 5 February 2013. **Cannonball example:
**if v_{0} is 100. m/s @ 30° and lands at launch height,* y =
y _{0}*. Find range

- If WMU is open Friday, we will have a normal class.
- With WMU Closed on Thursday, we'll take late Q4 papers on Friday, assuming normal classes.

Monday 2/4: (Apologies for being late to class due to slow speeds on the icy
roads. 2½ hours isn't a record, but it's up there.) **Types of Motion:
**No Motion (v=0, a=0), Uniform Motion (v=constant, a=0), Constant
Acceleration (a=constant). **Uniform Circular Motion (UCM)**: speed is
constant, but vector velocity is not; magnitude of the acceleration is
constant, but the vector acceleration is not. Velocity is tangent to circle,
Centripetal Acceleration is perpendicular to velocity and points radial INWARD.
a_{c} = v²/r. You can generate very large centripetal acclerations
very quickly. **Space Shuttle in Low-Earth Orbit**. (There's still gravity
up there!) Comments on Free Fall vs. "zero gravity" in space.

Tuesday 2/5: Exam 1. (Rescheduled from 2/1.)

- If you missed Exam 1, you need to email Dr. Phil so we can schedule a make-up exam.

Wednesday 2/6: **Demo**: Rodney Reindeer and U.C.M. The moment the
centripetal acceleration is zero, Rodney travels ballistically with an initial
velocity that is the last tangential velocity. **Examples:** A hard disk
drive spinning at 3600 rpm (60 times a second, time for one revolution = 1/60th
of a second). The guard around a circular saw blade takes the sawdust and
broken bits which shoot out tangentially from the blade and redirects them to a
bucket -- improves safety and makes less of a mess. **Recap**: Our studies
so far have described "How" things move, and allow to say
"When" and "Where" things move, but not "Why"
things move. For that we have to start talking about **Forces** -- and that
means Newton. Some stories about **Sir Isaac Newton**. (Reeding on the edge
of the silver shilling or a U.S. dime/quarter.) (Mad as a hatter -- from
mercury poisioning.)

Thursday 2/7: **Newton's Three Laws of Motion:** **Zeroeth Law -
**There is such a thing as mass. **First Law -** An object in motion tends
to stay in motion, or an object at rest tends to stay at rest, unless acted
upon by a __net external force__. **Second Law -** F=ma. **Third Law
-** For every action, there is an equal and opposite reaction, __acting on
the other body__. (Forces come in pairs, not apples.) SI unit of mass =
kilogram (kg). SI unit of force = Newton (N). English unit of force = pound
(lb.). English unit of mass = slug (Divide pounds by 32. For English units, g =
32 ft/sec².). Force is a vector.

- For a pair of equal and opposite forces -- it's First Law if they both act on the SAME object and Third Law if they both act on DIFFERENT objects.
- The problem with the First Law is that all too often, "an object in motion tends to come to a stop." But friction, as we shall see later, is an external force, which therefore makes that Second Law, not First. In the 1970s, NASA used some of the surplus Saturn V equipment to fashion a space station, Skylab. Videos: (drifting through Skylab), (Skylab launch, damage and repairs)

Friday 2/8: Quiz 5 in-class.

- Heavy wet snow Friday morning convinced me not to try to drive to Kalamazoo on a morning where I could get someone else to come in and administer the quiz. Sorry for any inconvenience, but I did give y 'all a heads up!
- For future reference: Why yes, we really CAN see where you are looking from the front of the lecture hall.

Monday 2/11: **Newton's Three Laws of Motion**. SI unit of mass =
kilogram (kg). SI unit of force = Newton (N). English unit of force = pound
(lb.). English unit of mass = slug (Divide pounds by 32. For English units, g =
32 ft/sec².). Force is a vector. **Free Body Diagrams.** Normal Force
(Normal = Perpendicular to plane of contact). The normal force does NOT
automatically point up and it is not automatically equal to the weight -- we
have to solve for the normal force. "*The Normal Force is NOT
automatically present -- you have to be in contact with a surface. The Normal
Force does NOT automatically point up -- F _{N} is perpendicular to the
surface. The Normal Force is NOT automatically equal to the weight.
F_{N} = mg only if there are no other forces in the
y-direction.*" Sum of forces in

- FIRST LOOK GRADES are input to the Registrar. This should show up on GoWMU as "Mid-Term Grades"? Please note that these grades are heavily influenced by Exam 1. I only gave an "E" grade to people who did not take Exam 1, otherwise the lowest estimated course grade recorded right now is a "D".
- First Sample Exam 2s on class web page.

Tuesday 2/12: "You can't push on a
rope." Since the force from a wire/string/rope/chain/thread/etc. can
only be in one direction, Dr. Phil prefers to call such forces T for Tensions
rather than F for Forces. Simple pulleys (Massless, frictionless,
dimensionless, only redirect the forces). "There is no free lunch."
The bracket for the pulley will have to support a force greater than the weight
of the hanging object. Mechanical advantage: multiple pulleys allow us to
distribute the net force across multiple cables or the same cable loop around
multiple times. Tension in the cable is reduced, but you have to pull more
cable to move the crate. **Elevator Problems.** The Normal Force represents
the "apparent weight" of the person in the elevator. For the elevator
at rest or moving at constant speed, the Normal Force = weight, and the tension
of the cable = weight of loaded elevator. But if there is an acceleration
vector pointing up, the apparent weight and the tension of the cable increase;
if the vector points down, the apparent weight and the cable tension decrease.
In true Free Fall, without any air resistance, the Normal Force = 0 and you are
floating. Article on the
1945
crash of a B-25 bomber into the Empire State Building and subsequent
elevator free fall.

Wednesday 2/13: **Elevator Problems.** The Normal Force represents the
"apparent weight" of the person in the elevator. For the elevator at
rest or moving at constant speed, the Normal Force = weight, and the tension of
the cable = weight of loaded elevator. But if there is an acceleration vector
pointing up, the apparent weight and the tension of the cable increase; if the
vector points down, the apparent weight and the cable tension decrease. In true
Free Fall, without any air resistance, the Normal Force = 0 and you are
floating. **Hanging a sign with angled wires** -- still the same procedure:
Sketch of the problem, Free Body Diagram, Sum of Forces equations in the x- and
y-directions, solve for unknowns. Discussion of **guy wires** to help
support a very tall antenna. **Atwood's Machine** -- two masses connected by
a single cable via a simple pulley. They share a common acceleration, *a*,
with one mass going up and the other going down. **More Elevator Comments.**
The Normal Force represents the "apparent weight" of the person in
the elevator. Like Atwood's Machine, we can hang a counterweight on a cable and
a pulley and support all or some of hte weight of the elevator. The elevator
will go one way and the counterweight will go the other way.

- For the sign problem, the equations are
- T
_{2}= T_{1}(cos30°/cos45°) - T
_{1}= mg / [sin30° + (cos30°)(sin45°)/(cos45°)

- T

Thursday 2/14: Return X1. **Two kinds of Friction:** Static (stationary) and Kinetic
(sliding). For any given contact surface, there are two coefficients of
friction, *µ*, one for static (µ_{s}) and one for
kinetic (µ_{k}). Static is always greater than kinetic.

- The "curve" for Exam 1 -- just add 3000 points to your score. But if your curved score was still less than 40,000 points, round it up to 40,000.

Friday 2/15: Quiz 6.

Monday 2/18: **Inclined plane problems:** Change the co-ordinate system,
change the rules. In the tilted x'-y'
coordinates, this is a one-dimensional problem, not two-dimensional.
Inclined plane with and without friction. **Finding the coefficient of static
friction by tilting**: μ_{s} = tan(θ_{max}). Similar
for kinetic friction, except one has to tap the board to "break the static
friction barrier". Rubber on concrete. Can μ be greater than 1? Means
θ_{max} greater than 45° -- rare, but yes. **Anti-Lock
Brakes and Traction Control.** ABS works by monitoring the rotation of all
four wheels. If one wheel begins to "lose it" and slip on the road
while braking, it will slow its rotation faster than the other tires, so the
computer releases the brake on that wheel only until it is rolling without
slipping again. This can be done many times a second, much faster than the good
old "pump your brakes to stop on ice" trick older drivers are
familiar with. Traction control uses the ABS sensors to monitor the wheel slip
during acceleration -- keeps the wheels from spinning.

- It is static friction in play when we are driving and have our vehicle under control, because the tread of our tire is lowered onto the pavement, does not slide, and then is lifted off. We often don't notice that the coefficients of friction have dropped greatly when it is slippery outside, until we need to steer or brake, and then we start skidding. Slow down! (grin)
- Link to Phil Plait's Bad Astronomy Blog about the Russian meteorite, the near miss asteroid and statistics and coincidences.

Tuesday 2/19: Dr. Phil canceled drive in and office hours due to slippery conditions + crosswinds. Prof. Michael Famiano came in to pinch hit and do some friction problems.

Wednesday 2/20: We are not done with Forces, but some problems cannot easily
be solved by using forces. Collisions, for example, are very complex if we have
to put in all the forces of bending and breaking and mashing things. Need a
simpler way of looking at the problem. "Inertia" is a word which
isn't used much today, but it is the same as "momentum" -- represents
some kind of relentless quality of movement. It takes a force to change the
momentum, otherwise it just continues on, i.e., Newton's 1st Law. Linear
Momentum ( p = mv ) is a vector quantity. **Newton's form of the 2nd Law:**
*F = δp / δt = change in momentum / change in tim*e instead of
*F=ma*, but really the same thing. **Impulse Equation:** δp = F
δt .**Two extremes in collisions: **Totally Elastic Collision (perfect
rebound, no damage) and Totally Inelastic Collision (stick together, take
damage). **Linear momentum is conserved in all types of
collisions **. **Totally Inelastic
Collisions**. Example: The Yugo and the Cement Truck with numbers. Real
Head-On collisions.

- ABC News video of a U.K. tanker truck with a car stuck on its front bumper. (Presumably NOT a head-on collision.)
- For Yugo and Cement Truck: m
_{1}= 1000 kg, v_{1}= 25.0m/s (to right), m_{2}= 30,000 kg, v_{2}= 25.0 m/s (to left). V = -23.4 m/s.

Thursday 2/21: **Linear momentum is conserved in all types of
collisions **.**Three example
collisions:** Head-on Collisions. Rear-end Collisions. (The Non-Collision --
if the car following is going slower, it isn't going to run into the car ahead.
PTPBIP.) 2-D Side Impact (vector) collision. Real crashes. **Interactions of
safety systems:** Seat belts, shoulder belts, steel beams in doors and
crumple zones. The myth of it being better to be "thrown clear from the
wreck". What happens in a wreck.

- For the wrecks today, Car 1 had m
_{1}= 1750 kg, v_{1}= 22.1 m/s, so p_{1}= m_{1}v_{1}= 38,680 kg·m/s ; Car 2 had m_{2}= 2340 kg, v_{2}= 16.5 m/s, so p_{2}= m_{2}v_{2}= 38,610 kg·m/s. Total mass of both cars, M = m_{1}+ m_{2}= 4090 kg. The head-on collision left the wreck with speed V = 0.171 m/s ; the rear-end collision had V = 18.90 m/s and the side-impact collision had V = 13.36 m/s and ¸ = 44.9°.

Friday 2/22: ~~Quiz 7~~. Course Reset... Discussion and Q&A
session of problems and communications issues in PHYS-1070 this semester.

- Quiz 7
~~In-Class~~Take-Home on Friction and Forces, handed out Friday 22 February 2013 and due on Tuesday 26 February 2013. - Quiz 8 Take-Home on Totally Inelastic Collisions, will be handed out on
Monday 25 February 2013 and due on Wednesday 27 February 2013 in class or by
Noon.
*NOTE: The date on this says Tuesday, but we'll collect them on Tuesday and Wednesday...*

Monday 2/25: An **explosion**. Or **recoil**. Example: A clown on
roller skates at rest -- when he hurls a pie to the left, he goes to the right.
Total momentum of the system remains constant (in this case, zero). **We've
talked about **How things move (Kinematic Equations) and Why things move
(Forces, momentum). Now we want to talk about the Effort to make things move
(Work and Energy). **Work: A Physics Definition **(Work = Force times
distance in the same direction). Work = Energy. SI units: (N)(m) =
(kg·m²/s²) = (Joule) = (J). Kinetic
Energy -- an energy of motion, always positive, scalar, no direction
information. Work-Energy Theorem (net Work =
Change in K.E.). Using the Work-Energy Theorem to find a final speed.

Tuesday 2/26: Return Q6. **Work: A Physics Definition **(Work = Force
times distance in the same direction). Work = Energy.
Power = Work / time.
Kinetic Energy -- an energy of motion, always
positive, scalar, no direction information. Work-Energy Theorem (net Work = Change in K.E.).
Using the Work-Energy Theorem to find a final speed. Potential Energy: Storing energy from applied work
for later. Gravitational P.E. = mgh. Location of h=0 is arbitrary choice.
Conservation Laws are very important in Physics. Conservation of
Total Mechanical Energy (T.M.E. = K.E. +
P.E.). Lose angle and directional information because energy is a scalar, not a
vector. We can change height for speed and vice versa. Conservation of T.M.E.
(P.E. + K.E.) on a **roller coaster**. Total energy limits maximum height.
If speed at top of the first hill is about zero, then this P.E. is all we have.
Cannot get higher, but we can change height for speed.

- Here's a quiz for my other class that you can use as a study problem on conservation of momentum. And its solution.
- Another Sample Exam 2 on the class web page.
- If Winter Storm Rocky keeps you from getting to WMU on Wednesday and
turning in your Q8 in class or by noon, email Dr. Phil the final answers to
"stop the clock" and get the hardcopy in at your next class. Example:
(a) 3.45 m, (b) 4.56 m/s, (c) 5.67 m/s^2.
*Don't scan your paper or take a photo and attach a large file to your email*.

Wednesday 2/27: **Demo**: a suspended bowling ball shows conservation of
T.M.E. All P.E. when swings up to a stop on either side, all K.E. at bottom of
swing. (There must be non-conservative forces, such as air resistance and
friction in the pivot point on the ceiling -- because the bowling ball never
quite gets up as high as it starts.) **Totally Elastic Collisions:**--
perfect rebound, no damage, conserve both momentum and K.E. The equations get
messy because each object has both an v_{i }and a v_{f}. Worse,
momentum is a vector and can have components, while K.E. is a scalar and a
square (½mv²).** Two special cases**: (1) m_{1} =
m_{2} , v_{2i} = 0, so v_{2f }= v_{1i} and
v_{1f} = 0. All the momentum and K.E. transfer from object 1 to object
2. (2) m_{1} = m_{2} , v_{1i} = - v_{2i} , so
they just bounce off each other and go the other way. **Close approximations,
Demo:** The Executive Time Waster. **Why you want inelastics collisions in a
wreck.** 5 mph versus 3 mph impact bumpers.

- We will NOT be doing Totally Elastic Collision problems.
**What if...**you made a car with soft, deformable body parts? So after a wreck you could just mold it back into shape? From Saturday Night Live: "Adobe: The Little Car Made of Clay".*Hulu video.*- NOTE: Normally my Thursday at Noon office hours are in the Help Room. However on Thursday 28 February 2013, I'll be in my office at noon, so that I'll be able to get to my Exam at 1pm on time.

Thursday 2/28: Exam 2.

Friday 3/1: WMU SPIRIT DAY -- No Classes.

- WMU Spring break next week. Our next class will be Monday 11 March 2013.

SPRING BREAK -- NO CLASSES.

Monday 3/11: Work = Energy. Power = Work /
time. **Power is rate that work can be done**. 1 horsepower = 1 h.p. =
the amount of work that one man, one horse and one plow can do in a day. An
engine with "more power" can either do the same work in less time, or
do more work. Conservation of T.M.E. (P.E. + K.E.) on a **roller coaster**.
Total energy limits maximum height. If speed at top of the first hill is about
zero, then this P.E. is all we have. Cannot get higher, but we can change
height for speed. **The Loop-the-Loop** on the roller coaster requires that
there be sufficient speed v (or K.E.) such that we meet the conditions of
Uniform Circular Motion at the top. The minimum speed occurs when the downward
pointing normal force from the track on the upsidedown cars goes to zero, and
the centripetal force, F_{c} = ma_{c} = mv²/r , comes only
from the weight, w = mg. Remember, that the centripetal force is a NET force,
i.e., F = ma is Newton's 2nd Law, so the net external force goes on the right
side of the sum of forces equations. **Example**: Rollercoaster with
h_{1} = 30.0 m, v_{1} = 0, h_{2} = 0 (bottom of
loop-the-loop), h_{3} = 12.0 m (top of loop-the-loop, making D = 12.0 m
and r = D/2 = 6.00 m). **Results**: v_{2} = 24.26 m/s, v_{3}
= 18.79 m/s. v_{3} is well above the minimum speed to safely do the
loop-the-loop (7.672 m/s from F_{N} = 0 and mv²/r = mg )

- If you need to take Exam 2 -- send an email to Dr. Phil immediately.
- Take the numbers for the rollercoaster and check them, using conservation of energy and U.C.M.
- A horsepower is based on the amount of work that one man and one horse and
one plow can do in one day. Of course, in the real world, there is a lot of
variation in horses, fields, plows, etc., so some horses can have power more or
less than 1 h.p. If you've seen the beginning to the movie
*War Horse*, you can have some idea of the suitability of having a thoroughbred race horse plowing a field.

Tuesday 3/12: **Newton's Universal Law of Gravity** (or
Newton's Law of Universal Gravity). **Use
Universal Gravity to check "g".** The value we calculate is close,
9.83m/s², which turns out to be only off by 0.2%. Why is it off? Because
using Univeral Gravity in this manner makes the assumption that the entire
Earth is uniform and homogenous from the surface to the core -- which it is
not. We would need calculus to integrate over layers to get the observed value
of 9.81m/s².** **UCM Revisited. **The Shuttle in Low Earth Orbit
(Revisited)**. Calculating g(r) for *r = 6,770,000 m* (the radius of the
Earth plus the height of 400 km for Low Earth Orbit), we get a value somewhat
different than we found for the centripetal acceleration. Working backwards, we
discover for this radius that the period *T = 5542 sec* and NOT the
estimated 5400 sec (90 minutes) we had started with before. **Newton's Law of
Universal Gravity + U.C.M:** Each radius of circular orbit has a different
value of g(r). As *r* increases, *v* decreases and *T*
increases. **Orbital mechanics:** Speed up and radius decreases, slow down
and radius increases. For the Moon, the period is around 28 days at a quarter
of a million miles away. **Geosynchronous orbits** occur when *T = 1
day* exactly, and for geosynchronous communications sattelites, the orbit
must be directly over the equator -- hence all sattelite dishes in the U.S.
face south.

- Finding the universal constant G was complicated by (1) the gravitational force between two ordinary objects is very small and (2) how do you figure out the mass of the Earth when you're standing on it?

Wednesday 3/13: **Newton's Law of Universal Gravity and Tides**
(high/low, spring/neap). Water is more flexible than land, so it can be
influenced by the weak gravitational forces from the Moon (a quarter million
miles away) and the Sun (93 million miles away). **We've asked: **How do
things move? (kinematics) Why do things move? (forces) What effort does it take
to move? (work and energy) Now we ask -- What moves? **Three Classical States
of Matter**: Solid, Liquid, Gas. Combinations: Condensed Matter (covers both
Solids and Liquids) and Fluids (covers both Liquids and Gasses). Note than in
the absense of chemical reactions, that the progression from Solid to Liquid to
Gas for a material goes from lower temperatures to higher temperatures. **Two
Extreme States of Matter**: Plasma (electrons stripped off, high
temperature), Cryogenics (extreme cold, odd behavior).

- That our oceans are all connected together and that the Moon's influence creates tides is very important to life on Earth. In particular, the boundaries between fresh and salt waters include marshes and estuaries, which are some of the most productive breeding grounds for creatures on the planet, in part due to the twice daily flushing effect of the tides to wash away wastes and flood in nutrients.

Thursday 3/14: Return Q7, Q8. **Extended Objects:** Mass occupies a
volume and shape. Mass-to-Volume Ratio
(Density). NOTE: Do not confuse the Density of the Materials with the
Mass-to-Volume Ratio of the OBJECT. Density of Water built into the SI metric
system (1 gram/cm³ = 1000 kg/m³). Sea water is 1030 kg/m³ ;
sugar water is 1060 kg/m³. **Floating on the Surface: **Mass-to-Volume
Ratio of the boat < Mass-to-Volume Ratio of the Liquid. Why Boats Float.
**Example**: Front lab table as a 250 kg boat with 4.00 m³ volume. Q9
Take-Home on Newton's Law of Universal Gravity, due on Monday 18 March 2013.

Friday 3/15: Return X2. **Water is unusual in two ways:**
(1) Water is *relatively* incompressible. If the
depth *h* isn't too deep, then the Mass-to-Volume ratio for water is
constant. For great depths, such as the bottom of the oceans, we can't use our
simple equation because rho is not constant. Air and gasses *are*
compressible, so we can't use our pressure from a column of fluid equation
either, though the air pressure here on the surface of the Earth is based on
supporting the weight of the column of air above us. (2) The
mass-to-volume ratio of ice (solid) is LESS than liquid water, so ice floats.
Ice which floats doesn't add to volume of water when it melts, but grounded ice
(non-floating) does. This is one of the reasons why people worry about what
global warming might do to the great ice sheets around the world.

Monday 3/18: **Archimedes and Eureka!** (I found it!) Using
mass-to-volume ratio and water displacement to determine if gold crown was
solid gold or not. **Floating on the Surface: **Mass-to-Volume Ratio of the
boat < Mass-to-Volume Ratio of the Liquid. Why Boats Float. Example: Front
lab table as a 250 kg boat with 4.00 m³ volume. Buoyant Force = Weight of
the Boat = Weight of the Water Displaced by the Submerged Part of the Boat.
Calculating the amount of the boat submerged, by using the fact that the mass
of the boat and the displaced water are the same. *Water is unusual in that
the mass-to-volume ratio of ice (solid) is LESS than liquid water, so ice
floats. Ice which floats doesn't add to volume of water when it melts, but
grounded ice (non-floating) does. This is one of the reasons why people worry
about what global warming might do to the great ice sheets around the world.
*Sinking of the RMS Titanic; Edmund Fitzgerald. Pressure = Force / Area. SI unit: Pascal (Pa).
Example: Squeezing a thumbtack between thumb and forefinger. 1 Pa = 1
N/m², but Pascals are very small, so we get a lot of them. One Atmosphere
standard air pressure = 1 atm. = 14.7 psi = 101,300 Pa.

- Q9 is a Take-Home on Newton's Law of Universal Gravity, handed out on
Thursday 14 March 2013, and due on
~~Monday 18 March 2013~~Tuesday 19 March 2013. - Table 4-4 of O&B shows mass-to-volume ratios of various materials: Lead (Pb) = 11,340 kg/m³; Gold (Au) = 19,300 kg/m³; Liquid mercury (Hg) = 13,600 kg/m³.
- Would really appreciate it if you don't watch the NCAA March Madness games during class... (evil grin) Because I can't while I teach. (bursts into sobs) (Not really, but I figure the "guilt thing" might work.)

Tuesday 3/19: **Water is unusual in two ways:** (1) Water is
*relatively* incompressible. If the depth *h* isn't too deep, then
the Mass-to-Volume ratio for water is constant. For great depths, such as the
bottom of the oceans, we can't use our simple equation because rho is not
constant. Air and gasses *are* compressible, so we can't use our pressure
from a column of fluid equation either, though the air pressure here on the
surface of the Earth is based on supporting the weight of the column of air
above us. (2) The mass-to-volume ratio of ice (solid) is LESS than liquid
water, so ice floats. Ice which floats doesn't add to volume of water when it
melts, but grounded ice (non-floating) does. This is one of the reasons why
people worry about what global warming might do to the great ice sheets around
the world. **Reset:** One Atmosphere standard air pressure = 1 atm. = 14.7
psi = 101,300 Pa. Pressure at a depth due to supporting the column of liquid
above. Absolute (total) Pressure vs. Gauge Pressure (difference between two
readings). Pressure due to a column of water = 1 atm. at h = 10.33m = 33.86
feet. **Absolute **(total) Pressure vs. **Gauge** Pressure (difference
between two readings). The perils of SCUBA diving. Using a column of liquid to
make a **barometer** to measure air pressure. Switch from water to mercury
changes h at 1 atm. from 10.33 m to 0.759m. The **aneroid barometer**.

- SCUBA = Self-Contained Underwater Breathing Apparatus -- invented by the famous Jacques Cousteau in WW II.

Wednesday 3/20: **How to get liquid out of a cup using a straw** -- or
why *Physics does not "suck"*, but pushes using a pressure
difference. **Smooth Fluid Flow: **Pressure from a column of liquid looks
like P.E. Create a Kinetic Pressure term which looks like K.E. and add in the
base pressure for total pressure to create Bernoulli's Equation and the Continuity Equation.
The Water Tower and the Faucet Problem. Why
the water tower needs a vent.

- Bernoulli's Equation, with six terms, is the longest equation of the semester. But like the Conservation of TME, upon which it is based, often we don't need all six terms and Bernoulli often simplifies to quite managable equations.
- Note that the solution to the water tower problem is the same equation as if I had just dropped the water from rest at the top of the water tower. (grin)
- During our "class reset" before break, we had a list of things we wanted to add. The Word of the Day (WOTD) mentioned in the beginning of every class is in case you need me to stop, get out of the way, repeat something, translate my handwriting or write bigger. (grin) However, no one has used it, so in case you forgot, here's your reminder. Also, here are some more problems to work on:
**Problems Chapter 4:**1, 5, 7, 13, 17, 27, 28.**Additional Problems 1-2.**(Click here for a copy.)

Thursday 3/21: Bernoulli's Equation and the
Continuity Equation. Want Smooth Continuous Flow, not Turbulent Flow or
Viscous Flow. *Flow rate = Volume / time = Cross-sectional Area ×
Speed*. The faster the fluid flow, the lower the Pressure. **Example**:
The aspirator -- a vacuum pump with no moving parts. **Example**: Air flow
around a wing. (Faster air over top means lower pressure on top, so net force
is up -- Lift.) **Spoilers** -- doors open in wing to allow air to pass
between upper and lower surfaces, thus "spoiling the lift" by
eliminating the pressure difference. Why the Mackinac Bridge has grates on the
inside north- and soundbound lanes. **Air Resistance**. Low speed and high
speed air resistance. If allowed to drop from rest, then a real object may not
free fall continuously, but may reach a Terminal
Velocity (Force of gravity down canceled by Drag force up) and doesn't
accelerate any more. Ping-pong balls versus turkeys (or pennies).

- The Discovery Channel's show
*Mythbusters*has, of course, done some episodes on things like the terminal velocities of pennies -- or falling bullets from guns fired straight up. The real world, as usual, is much more complicated than the simplified Physics we introduce here, but the concepts remain the same.

Friday 3/22: **Air Resistance**: Low speed and high speed air resistance.
If allowed to drop from rest, then a real object may not free fall
continuously, but may reach a Terminal
Velocity (Force of gravity down canceled by Drag force up) and doesn't
accelerate any more. Ping-pong balls in free-fall, vs. being hit with a paddle
in a world-class table tennis match. What is the terminal velocity of a falling
person? It depnds on clothing and orientation -- aerodynamics, streamlining,
cross-sectional area, composition of the air are all part of the drag
coefficients *b* and *c*.
World's
Record Free-Fall (old). (NEW
Sunday 10/14/2012)
**Problem:** Spray can. (Inside: P_{1} = 200,000 Pa, v_{1} =
0, h_{1} = h_{2}. Outside: P_{2} = 100,000 Pa. Find
v_{2}.) **Problem:** *RMS Titanic* is on the bottom of the
Atlantic, about 2½ miles down. When James Cameron made his movie, he rode
the Mir submersibles to the wreck. Find the speed of the water shooting into
the sub if there is a leak. Find the water pressure at that depth.
(P_{1} = P_{2}, v_{1} (on surface) = 0, h_{1} =
3821 m, h_{2} = 0, ρ_{seawater} = 1030 kg/m³.)
Actually the water pressure is higher, due to the fact that with hundreds of
atmospheres of pressure, the seawater is slightly compressed and so the
mass-to-volume ratio isn't constant, but increasing. Q10 Take-Home on
Mass-to-Volume Ratio and Bernoulli's Equation, due Tuesday 26 March 2013.
(Click here for a copy.)

Monday 3/25: **Temperature & Heat.** Heat = Energy. Two objects in
thermal contact, exchange heat energy, Q. If net heat exchange is zero, the two
objects are at the same temperature. **Temperature Scales**:
°F, °C and K (Kelvins).

Tuesday 3/26: Linear Expansion: Most
objects expand when heated, shrink when cooled. **Length Expansion.
Example:** One 39 ft. (12.0m) steel rail expands 5.88 mm from winter to
summer, but that's 0.75 meters for every mile of railroad track. **Expansion
joints. ****Linear Expansion:** Why "Bridge
Freezes Before Roadway" signs. Bridge expansion joints. Pavement
expansion joints.

- Table 5.2 on p. 179 of O&B shows coefficients of linear expansion (alpha) for some common materials.
**Problems Chapter 5:**3, 5, 6, 9, 13, 25, 27.**UPDATE:**Q11*will*be a Take-Home quiz. it*will*be handed out on Thursday 28 March 2013. There*will*be class on Friday 29 March 2013 -- it will be a problem solving session.

Wednesday 3/27: **Linear Expansion:** Pavement
expansion joints. I-57 in Chicago and the expanding asphault in 1983.
**Question:** Does the material expand into a hole when heated, or does the
hole expand? (Think about what happens to the disk removed from the hole --
does it expand or contract when heated?) Volume
Expansion of Solids and Liquids. Coefficient of Volume Expansion usually
given for liquids; for solids, β = 3α. **Ideal Gas Law** (PV/T =
constant or our form: P_{1}V_{1}/T_{1} =
P_{2}V_{2}/T_{2}) -- must use Kelvins for temp and
absolute Pressures, because neither P or T can be zero or negative.

Thursday 3/28: **Heat Energy (Q)** and Temperature Change & Phase Change. Add/remove
Heat Energy Q will raise/lower the temperature of a material using the
**Specific Heat** (J/kg·°C) for objects of mass *m*, or the
Heat Capacity (J/mole·K) for objects with *n* moles of atoms or
molecules. Add/remove Heat Energy Q will change its phase between
solid-liquid-gas using the **Latent Heat of Fusion**, *L _{f}*,
between solids and liquids, or the

- National Public Radio's Morning Edition story on Grain Silo accidents. Fluidized grain acting like a liquid in action...

Friday 3/29: **Problem:** A steel tea kettle has a volume of 2.00 L. At
20.0°C, is is half filled with water or 1.00 L. The kettle is sealed and
heated to 80.0°C. Using the equatinon volume expansion, ²steel =
3±steel and ²water = 207 × 10^{6} °C^{-1},
find the new volume of the kettle and the volume of the water. Finally,
consider the air sealed above the water. Initially, it's volume is 1.00 L, but
at 80.0°C, the volume is less, because the water expands more than the
kettle. Use P_{1}V_{1}/T_{1} =
P_{2}V_{2}/T_{2} to find the final pressure, assuming
the initial pressure was 101,300 Pa. **Problem**: Take a 1.00 kg block of
ice from the freezer (T = -20°C, about 0°F) and heat it in a pan
until it is all boiled away. Find the heat energy Q to: (1) Heat ice from
-20°C to ice at 0°C; (2) melt ice to water at 0°C; (3) heat
water from 0°C to 100°C, (4) boil water into steam at 100°C.
Using Power = Work/time, we can apply heat at the rate of 1000 W = 1000 J/sec,
and estimate how long each of these steps take. Ice has a low specific heat,
2000 J/kg·°C^{-1}, so ice very quickly warms up to the
melting point. The latent heat of fusion for melting ice / freezing water is
336,000 J/kg. Wet ice is at T = 32°F = 0°C = 273K. The specific heat
of water is 4186 J/kg·°C^{-1} = 1 Calorie (1 "Big
C" Calorie = 1 Food Calorie). This is the energy it takes to raise the
temperature of 1 kg of water by 1°C. (In the English system, we have the
British Thermal Unit, where 1 BTU is the energy it takes to raise the
temperature of 1 pound of water by 1°F. You see BTU ratings on air
conditioners and furnaces, for example.) "A watched pot never boils".
Water will boil in a pan for a long time. Indeed, the latent heat of
vaporization of water, 2,260,000 J/kg is huge and important for cooking and
putting out many fires. Water doesn't drown the fire, it removes heat from the
fire, lowering its temperature eventually below the ignition point. Can't use
water on all fires. Class D (magnesium) fires, electrical fires. Halon gas fire
supression systems protect computer hardware in a big data center, but displace
the breathable air -- get out when alarm sounds!

- Because the air in the tea kettle above inceases pressure, then if you have a whistling tea kettle, rather than a sealed container, the higher pressure will cause air to rush through the hole -- this will get fast enough when the water is boiling to create the whistle.
- If you look closely at a whistling tea kettle while it is whistling, there is a clear gap between the whistle and the billowy white clouds. The cloud is condensing water vapor, NOT steam. The steam is that jet of clear air in the gap. Do NOT put a dry finger in that gap, you will severely burn your finger, while the billowy white cloud many inches from the kettle will feel cool and damp.
- Take a 1.00 kg block of ice
from the freezer (T = -20°C, about 0°F) and heat it in a pan until it
is all boiled away.
*Note: Slightly different numbers than example given in class.* - Remember Exam 3 is next Friday!

Monday 4/1: **Heat content versus Thermal conductivity**.
Leidenfrost
Effect. **Thermodyanmics (Heat + Motion)** -- Moving heat energy Q
around. The Laws of Thermodynamics. **Zeroeth
Law** -- There is such a thing as temperature. **First Law** --
Conservation of energy. **Second Law** -- One cannot extract useful work
from a cyclic mechanical system without wasting some energy. **Entropy
examples** -- It takes work to clean or restore things. Left to themselves,
everything falls apart. The Heat Engine
and Three Efficiencies (Actual, Carnot and 2nd
Law).

Tuesday 4/2: The Heat Engine and
Three Efficiencies (Actual, Carnot and 2nd
Law). Fuel Economy (miles per gallon) is not an Efficiency. There is no
conspiracy to keep big 100 m.p.g. cars out of our hands. To use less fuel, do
less work. Reverse the arrows in the Heat Engine and you get a
**Refrigerator**. *NOTE: Cannot place an open refrigerator or a window air
conditioner in the middle of a room and cool the room, because the exhaust heat
to the hot side includes the heat pulled from the cold side plus the work done
on the compressor.*

- The actual efficiency turns out to be low. One way to raise the efficiency
is to change the temperatures of the reservoirs -- the Carnot effciency
(theoretical best case) can be raised by either raising T
_{H}or lowering T_{C}. - A typo on the last page of the Syllabus lists the last week as "15-18 April" instead of "15-19 April", which might lead some people to thinking there was no class on the last regular class day, despite no other place in the Syllabus or on the website saying that Friday was a No Class day. -- This is essentially the same typo as the last time.

Wednesday 4/3: Air conditioners and Heat Pumps.
Waves: **Single Pulse vs.
Repeating Waves**. The motion of the material vs. the apparent motion of the
wave. For Repeating Waves, we have a Repeat
Length λ (wavelength) and a Repeat Time T (Period). Frequency =
1/Period or f = 1 / T . Wave speed = frequency ×
wavelength ; v = f λ . The speed of sound in air: 334 m/s @ 0°C and
344 m/s @ 20°C. **Waves and Resonance.**
Standing Waves on a string.
Fundamental, First Overtone, Second Overtone, etc. **Demonstration**: the
Slinky shows both longintudinal (string type) and transverse waves (sound
type).

**General Reminder:**All semester long I have been talking about units, significant figures and showing all work. Just about everything put on the blackboard has complete equations, then solved for the problem. All numbers have their units at all times. Correct sig.figs. is applied, even to intermediate results. And grading is done accordingly.

Thursday 4/4: Review. Topic 2 Worksheets (Click here for 1st Worksheet and Directions)

- And Safety First! Do not try to write data down on Worksheet 1 while you are driving!
- Beginning Monday, April 8, the Course/Instructor Evaluation System (ICES Online) will open to students for the spring 2013 administration. (via GoWMU)

Friday 4/5: Exam 3.

Monday 4/8: **Waves and Resonance** continued.
Standing Waves on a string.
Fundamental, First Overtone, Second Overtone, etc. **Demonstration**: First
and higher overtones on a string driven by a saber saw. (Can't see the
Fundamental on the saber saw demo, because the tension required usually breaks
the string.) Standing Waves in a
tube. **Demo: **Getting Fundamental and overtones from twirling a
plastic tube open at both ends. (Pink tube missing - tried to use a shop vac
hose, too heavy, too slow.) **Demo**: Variable length organ pipe --
Fundamental and First Overtone (overblowing), varying pitch (musical note) by
changing length of tube open at only one end. Tuning forks, resonance boxes.
**Musical instruments: **Accoustic string instruments can change tuning by
changing the tension of the string and the string itself can be shortened on
the neck of violins, guitars, etc. Brass instruments start from the
"natural trumpet", which can only play the fundamental and overtones
for the pipe. Woodwind instruments get more complicated.

Tuesday 4/9: The range of "normal" human hearing: 20Hz-20,000Hz
(10 octaves). Resonance boxes, accoustic guitars. **Beat frequencies** occur
when two sounds have almost the same frequency -- get a distinctive
*wah-wah-wah *sound, whose *beat frequency = | f _{1} -
f_{2} |* . Takes time for sound to travel over a distance.
Constructive and Destructive Interference. Acoustics of concert halls.
The range of "normal" human hearing: 20Hz-20,000Hz (10 octaves).

Wednesday 4/10: **The speed of sound in air.** Sonic Booms and other
shockwaves. Bullwhip stories. Waves take
time to travel. Sound takes time to travel. An echo takes times to get to the
reflecting surface and travel back -- to and fro. The Realization that
**Electricity and Magnetism** were part of the same **Electromagnetic
Force** was a great triumph of 19th century physics. Greeks knew about static
electricity -- build up charge and get sparks.

- The Student Evaluation system (ICES) is now open for you. See the link at the top of this page.

Thursday 4/11: The **Two-Fluid Model of Static Electricity** (A & B),
to account for the two types of behavior noted. Franklin's **One-Fluid Model
of Electricity**. **Occam's Razor**: If you can't decide between two
competing ideas for how Nature works, take the simpler model.
Real Electric Charges. Two charges: like
charges repel, unlike (opposite) charges attract. Coulomb's Law looks like
Newton's Law of Universal Gravity. 1 Coulomb
of charge is an enormous amount of charge. Two 1.00 C charges separated by 1.00
meters have a force of nine-billion Newtons acting on each other. A Nickel coin
has a mass of 5 grams, so about 1/10th of a mole. Find number of Coulombs of
positive and negative charges. It's over 200,000 C! But... at the atomic level,
each nickel atom has the same number of electrons and protons, so overall each
atom and the whole nickel coin is charge neutral -- so not dangerous. **Four
Fundamental Forces in Nature:** Gravity, E & M, Weak Nuclear Force,
Strong Nuclear Force. **The Hydrogen Atom**. Gravity loses to Electric Force by a factor of 200
million dectillion (!!!). Q12 Take-Home on Standing Waves, due on Monday 15
April 2013. (Click here for a copy.) First
Day to turn in Topic 1 paper.

**Additional Problems 5-7.**(Click here for a copy.)

Friday 4/12: Return X3. **Four Fundamental Forces in Nature:** Gravity, E
& M, Weak Nuclear Force, Strong Nuclear Force. **The Hydrogen Atom**.
Gravity loses to Electric Force by a factor of 200
million dectillion (!!!). Likewise, the two
protons in the nucleus of the Helium Atom require the Strong Nuclear Force to
overcome the 231 N electric repulsion. **Isotopes** are the same element
(proton number Z), but with different numbers of neutrons (N). Some isotopes
are stable, some are unstable and undergo radioactive decay. If we didn't have
the Strong Nuclear Force making the Electric Force irrelevent inside the
nucleus, then the only element in the universe would be hydrogen. Second Day to
turn in Topic 1 paper.

- Remember -- Monday 15 April 2013 is the last day to turn in Topic 1 papers.
- Why April 12th is a significant day in the history of Soviet and American space programs.