*Updated: 18 December 2012 Tuesday.*

Estimated Pre-Finals Grades can be found here. FINAL COURSE GRADES AND BREAKDOWN BY CATEGORY FOR PHYS-1070 Fall 2012

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

Monday 12/10: Office Hours.

Tuesday 12/11: Office Hours.

Wednesday 12/12: Office Hours.

Thursday 12/13: FINAL EXAM (2:45pm-4:45pm)

Friday 12/14: LAST DAY TO MAKE UP EXAMS.

Monday 12/17: Office Hours.

Tuesday 12/18: Grades due at Noon.

Monday 9/3: Labor Day <No Classes>

Tuesday 9/4: Class begins. The nature of studying Physics. Science education in the United States. Natural Philosophy. The Circle of Physics.

Wednesday 9/5: Aristotle and the Greek Philosophers. Observation vs. Experiment - Dropping the book and the piece of paper (2 views). Mechanics is the study of motion. So what is motion? (Xeno) Zeno of Elea -- Zeno's Paradoxes.

Thursday 9/6: To understand the underlying concepts we need to Simplify The
Universe. "Speed Limit 70" -- what does it really mean? First
Equation: Speed = Distance / Time. v = d/t . Development of Speed equation for
Constant or Average Speed. delta-x = x_{f} - x_{i} . Distribute
syllabus.

~~Quiz 1 will be in-class on Friday 7 September 2012. It will be for attendance purposes. If you miss class on Friday, you will be able to get some of the points by downloading Quiz 1A from the website and turning it in~~.

Friday 9/7: Demo these class web pages. Discussion of Formula Cards. 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. * 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 (9.63 seconds) and World (9.58 seconds) record holder. He also has the
World Record in the 200 meter dash (19.19 seconds)).

- First use of i>Clickers in classroom -- Yay, it worked.
- Because we were running late, we didn't have time to do Quiz 1 on Friday, so:
- Quiz 1 will now be in-class on Monday 10 September 2012. It will be for attendance purposes. If you miss class on Monday, you will be able to get some of the points by downloading Quiz 1A from the website and turning it in.
- Quiz 2 will be in-class on Tuesday 11 September 2012.

Monday 9/10: 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). **Significant Figures** --
Although our calculators typical work with 12 digits and display 10 digits, a
10 digit measurement would have 10 significant figures. Such a measurement has
to cost at least a million dollars to make. A meter stick measured to 10
significant figures requires us to know where the last few atoms are on the
ends! We'll talk more about this on Tuesday. Topic 1 assigned. (Updated
Searchable booklist available online here .)
Q1 was in-class for attendance purposes. 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.)

**Remember:** PHYS-1080 Lab Begins This
Week.

NOTE: Monday 10 September 2012 -- Physics Help Room starts in 0077 Rood.

- Q2 will be in-class on v = d / t on Tuesday 11 September 2012. This will be your only non-metric quiz and Significant Figures will NOT be required.

Tuesday 9/11: 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. A simplified trip to the store -- The S-Shaped Curve.
Acceleration. 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.) Q2 in-class on *speed
= distance / time*.

- About a hundred years after the Antelope, in 1947, Chuck Yeager piloted the Bell X-1 and "broke the sound barrier" by design for the first time.
- I've been telling the story of the
*Antelope*for years, having learned about it in a kid's book on trains. Finally found a comment in Wikipedia, which says it wasn't five miles, but "First authenticated 60 mph, 26 miles in 26 minutes."

Wednesday 9/12: **The P-O-R (Press-On-Regardless)** road rally problem.
"You can't average averages." Comments on Q2 -- 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.

- The
**Physics Help Room**is now open in 0077 Rood (basement level, underneath the lecture halls -- use Southwest staircase). This semester the Help Room will be staffed with two people most of the time and open from 10-3 MTWRF.

Thursday 9/13: The Kinematic Equations for
Constant Acceleration. **The Equation Without Time** -- Avoiding the
Quadradic Formula. **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. Q3 Take-Home on the Kinematic Equations for
Constant Acceleration, due Monday 17 September 2012 in class or by 5pm.

- 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 |

Monday 9/17: **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* ;

**a = 1000 g for a millisecond:**Discovery Channel and YouTube come through! I've been telling the story of North American Aviation company test pilot Scott Crossfield and the static test stand explosion of the X-15 for years, and just now discovered that there's video online of this! You can see more successful flights of the three X-15 aircraft in this video and the first segment of this newsreel video. For more detailed shots of training, flights, landing, and the damage from a white covered X-15 flight that reached Mach 6.7, one last video. The X-15 lands as a glider, like the Space Shuttle, but it's a lousy glider. The only way the F-104 chase planes can follow it easily to the dry lakebed runway is to drop flaps and landing gear, and the X-15 still falls out of the sky like a brick. (grin)

Tuesday 9/18: **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.

- There are Sample Exam 1s on the class web page. The format for the hourly exams is two problems -- one multiple guess with 10 parts and one problem with 5 parts.

Wednesday 9/19: **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) Q4 Take-Home on Free-Fall motion in the
y-direction, due on Friday 21 September 2012 in class or by 5pm.

**Aviation majors:**We will be starting a daily sign-in form on Thursday. This comes from an FAA requirement.

Thursday 9/20: **Two Ways to Find Average Speed:** (1) v = d / t (always
works) ; (2) v_{ave} = (v_{0} + v) / 2 (works if a =
constant). **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. **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.

Friday 9/21: Finishing vector problems: (1) **Examples**: vector C =
vector A + vector B, 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. Quiz 5 is
a Take-Home on Vectors, handed out Friday 21 September 2012, and due on Tuesday
25 September 2012 in class or by 5pm.

- NOTE: The Office was closed for a while on Friday afternoon. If you were unable to turn in Q4, send me an email with the numbers of your final answers, and turn in the quiz on Monday. DO NOT send a scan of Q4.

Monday 9/24: **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.

- 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.

Tuesday 9/25: **Ballistic / Projectile Motion:** You can only use the
Range Equation if the landing height is the same at the launch height. If it is
not, you can still break the problem into two pieces and find the t and height
h at the turning point, then solve for the time from rest in the y-direction
down to the landing point, no matter whether it is above or below the launch
height. **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. Q6 Take-Home on Ballistic
Motion, and due on Wednesday 26 September 2012 in class or by 5pm.
*You can turn in Q5 at class on Wednesday 9/26 and Q6
at class on Thursday 9/27.*

- If you have to take a square root to get an answer, remember that there are two possible answers, plus or minus, to a square root.
- If you divide both sides of an equation by
*t*, then algebra says that t=0 is one of your solutions. - Class time was provided for going over some Sample Exam 1 problems, but not enough questions.

Wednesday 9/26: **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!)

Thursday 9/27: **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. **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.)

Friday 9/28: Exam 1.

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

Monday 10/1: **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. (Leftover from last week.)
**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. ("mad as a
hatter" from mercury poisoning.) **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.)

- If you missed Exam 1 last week, the easiest thing to do is come by Dr. Phil's office on Monday or Tuesday for afternoon Office Hours. I'll be there a little past 2pm.
- 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.

Tuesday 10/2: **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

- Please remember that the two take-home quizzes 7 and 8 need to be pulled apart from the staple, since they have different due dates. (grin)

Wednesday 10/3: Variations as we allow for an applied force that it at an
angle. Push down and Normal Force increases; pull up and Normal Force decreases
-- though it cannot go negative. "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. **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 "two pound test fishing line",
stretching and breaking of cables, Safety Factors.

- NOTE: You can turn in Q7 at class on Thursday 10/4.
- Phooey! There was a mistake on the board at the end of class today -- I
left off a sin45°. The correct pair of equations should be:
- T
_{2}= T_{1}(cos30°/cos45°) - T
_{1}= mg / [sin30° + (cos30°)(sin45°)/(cos45°)

- T
- Now assume we had a sign with m = 15.0 kg, then find the two tension
forces, T
_{1}and T_{2}tonight...

Thursday 10/4: **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 "two pound test
fishing line", stretching and breaking of cables, Safety Factors.
**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.

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

- T
- Now assume we had a sign with m = 15.0 kg, then find the two tension
forces, T
_{1}and T_{2}tonight... - Article on the 1945 crash of a B-25 bomber into the Empire State Building and subsequent elevator free fall.
- Expect to get Exam 1 back tomorrow...

Friday 10/5: Return X1. **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. Q9 Take-Home on
Pulleys and Tensions, due on Tuesday 9 October 2012, in class or by 5pm.

- Remember that the two tension forces, T
_{1}and T_{2}, from the hanging sign are still pending... - Exam 1A (yellow) had two errors in the solution handed out. (1) Problem
1(j) Kuril tosses another rock straight up at Standard Angle of... F=None of
these.
*We will fix this on Monday*. (2) Problem 2(b) Farmer Bob drives the first half of the trip (80.5 km)... the distance was fixed in the grading solution, but has 80.45 km in the solution handed out -- this does not affect any grades.

Monday 10/8: **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. **Rubber on concrete. **Tires rolling with friction on
good roads -- this is static friction not kinetic friction because the tires
aren't sliding on the pavement. If velocity vector and acceleration vector
point in the same direction, then the speed is increasing. If they are in the
opposite direction, then the speed is decreasing. In either case, for a car the
force involved must be in the same direction as the acceleration vector -- this
seems to be confusing whereby the static friction force on the tires from the
road points forward when you are speeding up. The conflict arises because you
might be thinking "friction opposes motion" and not thinking about
the motion of the tires versus the motion of the car. If object is at rest,
need to "test" to see if an applied external force exceeds the
maximum static friction force ("breaks the static friction barrier").
**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.

**Remember that the two tension forces, T**..._{1}and T_{2}, from the hanging sign are still pending- For the sign problem, the corrected equations are
- T
_{2}= T_{1}(cos30°/cos45°) - T
_{1}= mg / [sin30° + (cos30°)(sin45°)/(cos45°)

- T
- Now assume we had a sign with m = 15.0 kg, then find the two tension
forces, T
_{1}and T_{2}.

Tuesday 10/9: **Friction Examples** using our 125 kg crate sliding on the
floor. If object is at rest, need to "test" to see if an applied
external force exceeds the maximum static friction force ("breaks the
static friction barrier") and we switch to kinetic friction, or if static
friction "wins" then we remain at rest. Static Friction can vary from
zero to its max value in either direction. Kinetic Friction has only the one
value. If you push with a force equally the kinetic friction, you will move at
a constant speed. Otherwise you will either a positive or negative
acceleration. **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.

- T
_{2}= T_{1}(cos30°/cos45°) - T
_{1}= mg / [sin30° + (cos30°)(sin45°)/(cos45°)

- Now assume we had a sign with m = 15.0 kg, then find the two tension
forces, T
_{1}and T_{2}.

Wednesday 10/10: **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.
**Comments** on Runaway Truck Ramps and the optical illusion of The Mystery
Spot or Gravity Hill. We are not done with Forces, but some problems cannot
easily be solved by using forces. Next up: Collisions. Q10 Take-Home on
Inclined Planes and Friction, and due on Friday 12 October 2012, in class or by
5pm.

Thursday 10/11: 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. 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.

- First sets of Sample Exam 2 posted on class web page.
- Q10 -- each part has a different Free Body Equation and therefore a different sum of fcorces equation -- use them!

Friday 10/12: **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.
Q11 Take-Home on Total Inelastic Collisions, due on Tuesday 16 October 2012, in
class or by 5pm. *NOTE: We haven't talked about Kinetic Energy yet, so you
won't be able to finish the quiz quite yet.*

- Q10 -- Note that there are different Free Body Diagrams for parts a,b,c,
and therefore three different sums of forces equations.
**NOW DUE on Monday 15 October 2012**. - ABC News video of a U.K. tanker truck with a car stuck on its front bumper. (Presumably NOT a head-on collision.)

Monday 10/15: 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. How airbags work. **What's the opposite of a collision?** 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).
Kinetic Energy -- an energy of motion, always
positive, scalar, no direction information. We need this for Q11. Note that
Totally Inelastic Collisions, like all collisions, conserve momentum. But
Totally Elastic Collisions conserve both momentum and kinetic energy. In Q11,
we want to show that a great deal of kinetic energy is lost in the collision --
this is the energy available to do all the damage in the wreck.

Tuesday 10/16: **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'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: A Physics Definition
**(Work = Force times distance in the same direction). SI Units: (N)(m) =
(m·N) = (Joule) = (J). *Note: (N)(m) could be equal to (N·m), but
that's technically the SI unit for Torque -- a rotational force, so to avoid
confusion, Dr. Phil uses (m·N), or better yet, (J), for work and
energy.*

- NOTE: You can turn Q11 in at the start of class on Wednesday 10/17.
**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".*Alas, I cannot find the video itself online.*- Second Sample Exam 2 set posted on class web page.

Wednesday 10/17: **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.

Thursday 10/18: 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 ) **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.

- Trading height (PE) for speed (KE) and vice versa is standard practice in aircraft. Also utilitized on NASA's zero gravity simulators, affectionately known as the Vomit Comet. Most of the zero-gee scenes in the movie Apollo 13 were filmed on a NASA KC-135A.

Friday 10/19: **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). 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)
Work = Energy. Power = Work / time. **Power
is rate that work can be done**. 1 horsepower = 1 h.p. = 746 W = 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. **The Ballistic Pendulum** -- Old School Physics, in the days before
all our modern electronics: We can find the speed of a projectile through an
Inelastic Collision into a block of wood, followed by Conservation of TME, as
the block+projectile swings up and comes to a stop. Q12 Take-Home on
Conservation of Energy, due on Tuesday 23 October 2012, in class or by 5pm.

- 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. - 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.

Monday 10/22: **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.) **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. **Four Fundamental Forces in Nature: **Gravity, E & M,
Weak Nuclear Force, Strong Nuclear Force. Surprisingly, gravity is the weakest
of these, but it holds the universe together because things like planets, stars
and galaxies have so much mass. ** **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.
Each radius of circular orbit has a different value of g(r). As *r*
increases, *v* decreases and *T* increases.

- 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?
- Remember that Exam 2 is on FRIDAY 26 October 2012. (1) We'll take questions from the Sample Exam 2s in class on Wednesday. (2) If you are taking Exam 2 at the Testing Center, make sure you've reserved your time and send me an email so I can have an exam there for you.

Tuesday 10/23: **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. **Newton's Law of Universal
Gravity and Tides** (high/low, spring/neap). **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.

- Universal Gravity is the last topic for Exam 2 material.
- 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.
- We'll take questions from the Sample Exam 2s in class on Wednesday.
- NOTE: An error had a Sample Exam 3 posted on the class web page. The "Third Set" now there is a Sample Exam 2.
Please note that the Physics Help Room will temporarily move from 0077 Rood Hall to 2240 Rood from Wednesday 24 October 2012 to Friday 26 October 2012.

Wednesday 10/24: **Three Classical States of Matter**: Solid, Liquid,
Gas. Combinations: Condensed Matter (covers both Solids and Liquids) and Fluids
(covers both Liquids and Gasses). **Two Extreme States of Matter**: Plasma
(electrons stripped off, high temperature), Cryogenics (extreme cold, odd
behavior). **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). Floating on the Surface: Mass-to-Volume Ratio of the boat
< Mass-to-Volume Ratio of the Liquid. Review for X2.

- Please note that the Physics Help Room will temporarily move from 0077 Rood Hall to 2240 Rood from Wednesday 24 October 2012 to Friday 26 October 2012.

Thursday 10/25: **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. 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.

- Please note that the Physics Help Room will temporarily move from 0077 Rood Hall to 2240 Rood from Wednesday 24 October 2012 to Friday 26 October 2012.

Friday 10/26: Exam 2. Q13 Take-Home on Floating and Pressure, due on
Wednesday 31 October 2012, in class or by 5pm. (Click
here for a copy.) *Yes, I know it says it's
due on Tuesday, but there's material we have to cover on Monday first.*

Monday 10/29: **Archimedes and Eureka!** (I found it!) Using
mass-to-volume ratio and water displacement to determine if gold crown was
solid gold or not. 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. 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.

- Physics Help Room should have been moved back to 0077 Rood as before.
- Table 4-4 on p. 145 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.
- In part because of the possibilities of weather issues locally from Hurricane Sandy and the "Frankenstorm", Q13 is now due on Wednesday 31 October 2012.

Tuesday 10/30: **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**. How
to get liquid out of a cup using a straw -- or why *Physics does not
"suck"*, but pushes using a pressure difference.

- Q13 now due Thursday 1 November 2012 -- we have one more thing to cover on Wednesday.
- SCUBA = Self-Contained Underwater Breathing Apparatus -- invented by the famous Jacques Cousteau in WW II.

Wednesday 10/31: **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.
Water Tower and the Faucet Problem. Why the
water tower needs a vent. 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.

- Please note that the Physics Help Room will
temporarily move from 0077 Rood Hall to 2240 Rood from Wednesday 24 October
2012 to
**Friday 2 November 2012**. - 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)

Thursday 11/1: 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. **Pressure Considerations: **Why the
steel bands wrapped around an old fashioned water tower or a farm silo are
closer together at the bottom than at the top. A farm silo holds grain, which
like sand, etc., is made up of solids but in small particles. Such flowable
solids or fluidized solids can act like fluids and be piped around.

- Q13 Comment:
*When we did the roller coaster example in class, we had the cars moving very slowly at the top of h*_{1}, so that v_{1}was approximately zero. That meant it was all PE and no KE. If we invoke conservation of TME and have no friction or air resistance, the roller coaster cars can never go higher than h_{1}. Now consider the cartoon version of a small boat with a hole in it -- you get a huge fountain of water shooting up from the bottom and ending up much higher than the boat. But can it do that? If the water coming in at the bottom is all kinetic pressure and no potential pressure, and P_{1}= P_{2}, then the water not only can't go higher than the sides of the boat -- it can't go any higher than the waterline, where it is all potential pressure and no kinetic pressure, by conservation of pressure (Bernoulli). Now, just show this

Friday 11/2: Return X2. **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).

- X2 Curve is located here. (Wouldn't print before class on Friday.)
- Note that (1) Hot and Cold are relative terms and (2) Heat in Physics means Heat Energy -- there is no Cold, just less Heat.

Monday 11/5: 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.
- We will fix grades for certain grading issues on X2 Problems 2c (sig. figs) and 2e (Conservation of Energy equation) on Tuesday in class.
- Several people have wondered why, on X2 Problem 2c, they lost points when
they "had the right equation". V = m
_{1}v_{1}/ (m_{1}+ m_{2}) . Actually, you lost points because you didn't show all your work, you weren't doing Physics. That equation solves a particular problem. The proper solution starts from p_{before}= p_{after}and m_{1}v_{1}+ m_{2}v_{2}= (m_{1}+ m_{2}) V . Dr. Phil does not endorse using "cookbook Physics".

Tuesday 11/6: **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, beta = 3 × alpha. **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.

Wednesday 11/7: **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

Thursday 11/8: 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! **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.

Friday 11/9: The Heat Engine and Three Efficiencies (Actual, Carnot and 2nd Law). Q15+16 Double Take-Home on Heat Capacity and the Heat Engine, due on Wednesday 14 November 2012, in class or by 5pm.

- As we'll see on Monday, miles per gallon (m.p.g.) is NOT an efficiency.
- 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}.

Monday 11/12: 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}. - Don't forget about the Double-Quiz Q15+16 -- due Wednesday!

Tuesday 11/13: 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 (wavelength) and a Repeat Time (Period).
Frequency = 1/Period or f = 1 / T . Wave speed = frequency
x 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). 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.)

Wednesday 11/14: **Waves and Resonance** continued.
Standing Waves on a string.
Fundamental, First Overtone, Second Overtone, etc.
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. **Demo**: Tuning forks require
both tines to work -- the "sound of a tuning fork with one tine" is
that of silence. **Demo:** Resonance box tuned to tuning forks. Musical
instruments: Accoustic string instruments have a resonance box. Brass
instruments start from the "natural trumpet", which can only play the
fundamental and overtones for the pipe. Woodwind instruments get more
complicated.

Thursday 11/15: Musical instruments: Accoustic string instruments have a
resonance box. Brass instruments start from the "natural trumpet",
which can only play the fundamental and overtones for the pipe. Woodwind
instruments get more complicated. **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).

- Video: The Tacoma-Narrows Bridge Disaster. Page down to see the video -- it has NOT been speeded up.
- Find out which ultrasonic
ringtones you can hear! Dr. Phil's result today: "
." Considering I'm age 53, I'll take it. (grin)**You are a thirtysomething**. You're a little frustrated that you can't hear all the tones that the young 'uns can but will be more than happy if it means you don't have to listen to their damn ringtones on the bus anymore. The highest pitched ultrasonic mosquito ringtone that I can hear is 14.9kHz - NOTE 2: Technically, any of the sounds you can hear from 14kHz to 20kHz are within the range of human hearing, and by definition are NOT ultrasonic.

Friday 11/16: Return some Qs. Reminder: Dr. Phil's Simplified **Significant
Figures** for multiplication, division and trig functions. (Click
here if you need a copy.) **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. 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!

Monday 11/19: Return Q13. **Sonic Booms** and other
shockwaves. 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. Review.

- When we come back from Thanksgiving, we will continue talking about Electricity and Magnetism -- and you'll begin to see what Dr. Phil means by saying that Physics really is cummulative and One Big Physics. (grin)

Tuesday 11/20: Exam 3.

Wednesday 11/21: WMU Classes end at Noon -- Class does not meet.

Thursday 11/22: Thanksgiving Day. No classes.

Friday 11/23: No classes.

Monday 11/26: Greeks knew about **static electricity** -- build up charge
and get sparks. 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. **Four
Fundamental Forces in Nature: **Gravity, E & M, Weak Nuclear Force,
Strong Nuclear Force. **The Hydrogen Atom.** Real Electric Charges. Two charges: like charges
repel, unlike (opposite) charges attract. Coulomb's Law looks like
Newton's Law of Universal Gravity.

- If you missed Exam 3 on Tuesday 20 November 2012, please contact Dr. Phil as soon as possible to take a make-up exam.
- Sample Final Exams are starting to appear on the class web page. Note that there is still two weeks of new material coming.
- Topic 1 Book Reports can be turned in on any of these three days: (1) Thursday 29 November 2012, (2) Friday 30 November 2012 or (3) Monday 3 December 2012. Papers turned in after that will be assessed a 10,000 point/day penalty.
- Today is the last day to turn in a Draft paper, if you wish to.
- Remember the Topic 2 worksheets!
- The Student Evaluation system (ICES) is now open for you. See the link at the top of this page.

Tuesday 11/27: 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 (!!!). Q18 Take-Home on Electric Charges and Electric
Force, due on Thursday 29 November 2012, in class or by 5pm.

Wednesday 11/28: **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. **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

Thursday 11/29: **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!

Friday 11/30: **Conductors** (metals) versus non-conductors
(**insulators**). **Semi-Conductors** sit in the middle. Sometimes they
conduct and sometimes they don't. This means they act like a switch or valve,
and this is the basis for the entire electronics semi-conductor industry.
**D.C. Electrical circuits.** Ohm's Law.
V=IR form. (Ohm's "3 Laws"). **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. Second day to accept finished
Topic 1 Book Reports. (Last day to accept without penalty is Monday 3 December
2012 by 5pm.) Remaining Topic 2 Worksheets handed out. (Click
here for a copy.) Q19+20 Double Take-Home on
Electric Potential and Series & Parallel Resistors, and due on Tuesday 4
December 2012, in class or by 5pm.

Monday 12/3: Return X3. **The Simplest Circuit: **Battery, wires, load
(resistor). Power dissipated by Joule heating in a resistor. P = I V (3 forms
of Power equation to with Ohm's "3 Laws").
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. Last day to accept finished Topic 1 Book Reports without
penalties -- unless you had Dr. Phil look at a Draft Paper.

- Reminder: Dec. 13 Thu - Final Exam 2:45-4:45pm (2 hours)

Tuesday 12/4: **"Magnetism is just like Electricity, only
different." **Real Magnets are dipoles (North and South ends, linked).
Break a magnet in half, and you either get two new magnets -- or nothing.
So far, there is no evidence that there are Magnetic
Monopoles (magnetic charges: isolated North or South poles). Rules
similar to Electric Charges: **Unlike poles attract, like poles repel**.
Dropping a permanent magnet can result in a reduction of its** magnetic field
(B-field)** as the shock allows some iron atoms to flip 180° and
therefore cancel instead of add to an adjacent iron atom's magnetic field. The
horizontal compass needle rotates until its North end points North (or rather
to the North Magnetic Pole, which is of course a South pole of the Earth's
magnetic core); the vertical compass rotates so that it lines up with the
B-field along the surface of the Earth at the point. At the Equator, the
vertical magnetic should be parallel to the ground, at the magnetic poles, it
should be perpendicular to the ground. Is the Earth's magnetic field going to
flip some day? And what about Mars? SI Units for B-field: (1 Tesla = 1 T).
"Other" unit for B-field: ( 1 Gauss = 1 G ; 1 T = 10,000 G ). Earth's
B-field is about 1 Gauss at the Earth's surface. Example of the 4T NMR magnet
at Michigan Tech and the 10-foot radius line on the floor and erasing ATM cards
within that circle. The Great 19th Century Debate: **Is Light a Particle or a
Wave**? (Wave-Particle Duality did not seem obvious at the time.) The
**Electromagnetic Wave** travels at the speed of light. c = 300,000,000 m/s
= 186,000 miles/sec. **Electromagnetic Spectrum**: Visible light
(ROYGBIV=red orange yellow green blue indigo violet). Visible light is 400nm to
750nm (4000 angstroms to 7500 angstroms). Cannot "see" atoms with
visable light, because the atom is about 1 angstrom across (1.00E-10 meters).
The visible light wave is too large to see something that small. Frequences
LOWER and wavelengths LONGER than visible light (IR infrared, Microwave, Radio
waves, ELF extremely low frequency). Microwave ovens have
metal screens in their windows -- the centimeter-range sized EM waves cannot
see the "small" holes in the screen, so they bounce off the window as
if it were just like the metal in the other five walls. Discussion of how
microwave ovens "cook" food. Frequencies HIGHER and
wavelengths SHORTER than visible light (UV ultraviolet, X-rays, Gamma
rays). UV-A and UV-B, tanning and the problem of cheap
sunglasses. Images inside object using X-rays passing through or scattering or
being absorbed by the object. Why Superman's X-ray vision cannot work --
because everyday situations are "dark" in the X-ray band, thankfully!

Wednesday 12/5: More on the **E-M Spectrum**. **The Wave-Particle Nature
of Light. **As a wave, light has a wavelength, a frequency and a wave speed,
c = f λ = 300,000,000 m/s. **The energy of a single photon**
("particle" of light) is *E = h f*, where *h = 6.626 ×
10 ^{ -34} J·s *is Planck's constant, a fundamental constant
involved in Modern Physics. (If there was only Classical Physics, then

- Due to time constraints, we obviously have not covered all the material in the text. If you want a rough guide to the topics we didn't cover at the end of the textbook, check out these topics from the PHYS-1150 course.
- REMEMBER: Topic 2 Worksheets due on Thursday 6 December 2012.

Thursday 12/6: Return Q17-18. The Law of
Refraction - Snell's Law. Light bent at the interface between two media,
because the speed of light changes in the media. (Analogy: If you are driving
along the road and your right tires go off onto the soft shoulder, they can't
go as fast and the car turns towards the shoulder until all four wheels are
driving off the road.) Light offset going from air to glass to air in a
parallelo-plano sheet of glass. If going from an high index of refraction media
to a lower index media ONLY, may split light into the rainbow colors of the
spectrum -- **Dispersion** has to do with a slight variation in the speed of
light in a media for every wavelength. Also get a chance for
Total Internal Reflection (T.I.R.). This is a
"perfect" reflection, better than a mirror. Used in high-end optical
systems instead of mirrors. Also useful in fiber optics cables. **Quantum
Mechanics**. *... The Bohr atom... Coulomb's Law combines with Uniform
Circular Motion and the Modern Physics concepts of the deBroglie wavelength
(matter also has wave-particle duality) and quantum physics (like the stepped
terraces of our lecture hall, 1104 Rood, the electron cannot exist at just any
energy level or radius from the nucleus) .*Topic 2 Worksheets due TODAY.

Friday 12/7: Review. Q22 in-class quiz.

- FINALS WEEK Office Hours are posted here.