*Updated: *29 April 2014 Tuesday*.*

FINAL COURSE GRADES AND BREAKDOWN BY CATEGORY FOR PHYS-1070 Spring 2014

Monday 4/21: Office Hours.

Tuesday 4/22: FINAL EXAM (10:15am-12:15pm) Office Hours.

Wednesday 4/23: Office Hours.

Thursday 4/24: Office Hours.

Friday 4/25: LAST DAY TO MAKE UP EXAMS. Office Hours.

Monday 4/28: Office Hours.

Tuesday 4/29: Grades due at Noon.

Monday 1/6: First class canceled by winter storm.

Tuesday 1/7: First class canceled by winter storm and dangerous cold and wind chills.

Wednesday 1/8: Class FINALLY begins. The nature of studying Physics. Science education in the United States. The Circle of Physics.

- Physics Help Room opens today -- 3302 Rood.
- The Tuesday PHYS-1080 Lab section will do the Info Day activity as part of their Lab 1 on Tuesday 1/14. All other lab sections meet as planned this week.

Thursday 1/9: 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. Distribute Syallabus.

- Dr. Phil's Noon Office Hour will be held in the Physics Help Room 3302 Rood.
- Dr. Phil's 1pm Office Hour will be cut short as I have to leave for a Physical Therapy (PT) appointment. Relearning to walk is hard work!
- 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. Our lab sections are currently full. We have about ten people on the waiting list who need to co-register PHYS-1070/1080, but cannot unless some people drop.
- Quiz 1 will be on TUESDAY 1/14, due to our two snow days this week.

Friday 1/10: First Equation: Speed = Distance / Time. v = d/t . Development
of Speed equation for Constant or Average Speed. delta-x = δx =
x_{final} - x_{initial} = x_{f} - x_{i} , x =
x_{0} + v t . (**Restrictions:** This last equation is for constanr
or average speed only.)

- READING: Start reading Chapter 1 until your eyes glaze over or you have trouble following it. Like I said in class, I have issues with Chapter 1, so if you lose the train of thought, it's not you. (grin)

Monday 1/13: **PTPBIP - Putting The Physics Back Into The Problem**.
English system of measurement. SI Metric System. Prefixes. What do we mean by Measurements?
"Units will save your life."

Tuesday 1/14: Xeno's Paradoxes. Discussion of formula cards. 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). 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.

Wednesday 1/15: **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. **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.)

Thursday 1/16: **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 = δv / δt* is for constant or average
acceleration. Finding the set of Kinematic
Equations for Constant Acceleration.

- Because of our late start, Q2 will be a Take-Home, handed out on Friday 1/17 and due Tuesday 1/21.

Friday 1/17: The 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. Topic 1 assigned. (Updated Searchable booklist available online
here .) Quiz 2 is a Take-Home on the Kinematic
Equations, due Tuesday 21 January 2014 in class.

- Remember, no classes on Monday due to MLK Day Activities.
**Example from class:**A car accelerates from rest to 60 mph (26.8 m/s) in a distance of 255 m. What is*a*? What is*t*?- The kinematic variables become:
*x*_{0}= 0, x = 255 m, v_{0}= 0, v = 26.8 m/s, a = ?and t = ? - Answers:
*a = 1.408 m/s² , t = 19.03 sec*. We checked*t*by using both Kinematic Equations (1) and (2). - The
**Equation Without Time**is generated by combining Kinematic Equations (1) and (2) to eliminate*t*as a variable. You should try this at home! - NOTE: The 4 Kinematic Equations given in class are not in your textbook in
this form. There are two problems with Chapter 1. (1) It seems to assume you've
already had some Physics all ready, so it covers too much material, too fast.
(2) It also falls short of the Kinematic Equations, treating our three simplest
motions as separate phenomenon (no motion x = x
_{0}; constant speed x = vt from x_{0}= 0; constant acceleration x = ½at² from v_{0}= 0, x_{0}= 0), instead of allowing you to accelerate even if are already moving. (!!) - What Dr. Phil is giving you is more complete and more useful -- and ultimately easier to understand.

Monday 1/20: **MLK Day to Honor Dr. Martin Luther King, Jr. **-- Classes
Do Not Meet at WMU -- University-wide activities.

Tuesday 1/21: Return Q1½. Collect Q2. **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.
**Revisit: 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 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). **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.

- 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 |

Wednesday 1/22: **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* ;

**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)- 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.

Thursday 1/23: **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* ;

- Weather report I heard for Friday on the drive home is snow and high wind
gusts
*in the afternoon*.

Friday 1/24: Tallk about Sample Exam 1s. Discuss how to use the **mph and
sec/mile chart** seen in the multiple-guess problems. **The consequences of
Falling Down... ...and Falling Up**. The Turning Point ( *v _{y} =
0*, but

Monday 1/27: Classes canceled by winter storm.

- Quiz 3 will be due the day AFTER we get back. This is in case we have to cancel Tuesday classes due to wind chills as well. I want to have a day where questions can be answered before turning in.
- NOTE: There is a good chance Tuesday classes may be cancelled due to severe winds and wind chills starting after 4pm Monday through 7pm Tuesday. Just sayin'.
- As of Monday, all of the Sample Exam 1s have been posted.

Tuesday 1/28: **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.
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).

- Dr. Phil is not driving in today -- as of 9:22am we are working on setting up lecture in 1110 Rood via Skype.
**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.- 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 actua; Exam 1 will only be on material we've covered.
- For the guy with the fedora and the cigar. x
_{0}= 0, x = 8.00 m, v_{0x}= v_{x}= ?, a_{x}= 0, t = ?, y_{0}= 20.0 m, y = 0, v_{0y}= 0, v_{y}=?, a_{y}= - g, - For the Cop and the Speeder. x
_{10}= 0, x = ?, v_{10}= v_{1}= 40.0 m/s, a_{1}= 0, t = ?, x_{20}= 0, x_{2}= ?, v_{20}= 0, v_{2}=?, a_{2}= +3.00 m/s². - First attemp at making audio versions of lectures, since a lot of people could not be there today. These are not compact files. Do let me know if they are usable. Note that I pause a lot so you can keep up with your notes.

Wednesday 1/29: Return Q2. **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). Note that (1) if you take
a suqare root of *t *, you get two answers, +/- , (2) if you divide both
sides of an equation by *t* then *t = 0* is also a solution. In both
cases, these other solutions may not be useful to our problem, because they
occur at the beginning or before the problem starts -- the equations go on
forever in the past or the future, but the problem is defined only over a
narrow range.

**Apologies**-- took nearly three hours to get in today. I did call ahead to get the room opened and alert everyone that I was coming in, but being shortstaffed, that didn't happen. Some people bailed after the "fifteen minute rule", even though the syllabus points out I will try to get there.**QUIZ 3:**Yes, I will accept them on Thursday.**EXAM 1 and QUIZ 4**in the Syllabus will be swapped.**Exam 1 will be Friday 7 February 2014**.**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. If you've already scheduled for 31 January, you have to reschedule for 7 February.

Thursday 1/30: **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.

- Note that the lecture on vectors may be the single hardest concept all semester -- so if you have questions, you are probably not alone!
- Please note -- the whole presorting of quizzes into one of the 5 sections
27a to 27e works really well if you actually
__circle your section__under your name so people can easily figure out if it's in the right pile.

Friday 1/31: **Exam 1 moved to Friday 7 February
2014**. .**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 Vectors and the Analytic Method, due Tuesday 4
February 2014.

Monday: 2/3: **The guy with the fedora and the cigar (Revisited)**.
Finding final velocity of problem with the guy with the fedora and the cigar in
Standard Form. **Another Vector Problem:** A_{x} = -3.17 m and
A_{y} = -4.55 m. Formula cards.

- Dr. Phil is not driving in today -- 12 miles in and my brakes failed. Turned around and went to Chevy. Skyped the lecture.
- Another set of audio versions of the lectures.

~~NOTE: I have Physical Therapy at 3:45 in Allendale, so need to leave by 1:45pm.~~

Tuesday 2/4: **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.

- NOTE: I have Physical Therapy at 3:00 in Allendale, so need to leave by 1:15pm.
- '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.

Wednesday 2/5: Return Q3. **Cannonball example: **if v_{0} is
100. m/s @ 30° and lands at launch height,* y = y _{0}*. Find
range

- And... the Q4 solution I posted yesterday had a couple of mistakes. I must've been interupted while I was working on it.
- Very pleased that a number of students finally came to Office Hours -- I was busy from 11am to after 1pm.

Thursday 2/6: **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.

- NOTE: Noon Office Hour is in the Physics Help Room and I have Physical Therapy at 3:45 in Allendale, so need to leave by 1:45pm.
- My sketch of the Space Shuttle in orbit has 3 flaws. The first being no human has ever orbited the Earth in polar orbit (going strictly north and south), though the US Air Force planned to launch Space Shuttles into polar orbits from Vandenberg AFB before the Challenger disasater.
- Sidebar discussion of the sketch of the Space Shuttle in Low Earth Orbit (LEO) -- and the book Shuttle Down by Lee Correy
- Class time was provided for going over some Sample Exam 1 problems, but not enough questions.
- A student who came by Office Hours left their whiye index cards Formula Card in my office -- I will bring it to the exam on Friday.
- Webcomic xkcd on Centrifugal vs. Centripetal Force. (I thought I remembered it being Goldfinger, but I guess Randal used his usual troublemaker with the hat.) (grin)

Friday 2/7: Exam 1. (Rescheduled from last week.)

Monday 2/10: U.C.M. **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.

- For an early hard drive with platters 14" in diameter: D = 14", r
= D/2 = 7.00" = 0.1778 m. 3600 rpm = 60 revs per second. T = 1/60 revs per
sec = 0.01667 sec. v = d / t = C / T = (2πr)/T = 67.03 m/s or about 150 mph.
a
_{c}= v²/r = 25,270 m/s² or 2576 g. You can generate very large centripetal acclerations very quickly. **The Real World (Reminder):**Go to the Library, the magazine section of a book or grocery store, or a personal collection. Look for automobile magazines like*Road and Track*,*Car and Driver*, etc. Perhaps about 1/3 of the way in, look for a performance review of a new car with a graph of v vs. t under maximum acceleration conditions on a track. Note how the graph looks, as opposed to our Time Regions I and II in our S-Shaped Curve simplified trip. Do you understand why the real graph looks like it does?- Some thoughts on February 1964 -- fifty years ago.
- If you missed Exam 1, you need to email Dr. Phil so we can schedule a make-up exam.

Tuesday 2/11: **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. **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.)
**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.)

Wednesday 2/12: **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

Thursday 2/13: 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

Friday 2/14: Exam 1 returned. Q5 in-class. Q6 Take-Home on Forces and Free Body Diagrams, due Wednesday 19 February 2014.

Monday 2/17: "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.

- Hint for Q6 due on Wednesday -- Remember that Forces are Vectors -- they
have direction and
*x*- and*y*-components.

Tuesday 2/18: **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
- You should use both equations from the Atwood's Machine problem to find the
tension
*T*and check that they give you the same answer. (m_{1}_{1}= 5.00 kg ; m_{2}= 7.00 kg ; we found that the common acceleration was*a = g/6*) - I've been meaning to recommend some book Problems for some time. You can do more Problems or none -- this is not homework to be turned in and graded. Note that odd numbered Problems have answers in the back of your textbook.
**Chapter 1 (Kinematics and UCM):**1.8, 9, 10, 13, 17, 18, 19, 20, 22, 23, 24, 27, 28, 29.**Also... Challenges 1.4.****Chapter 2 (Newton's Laws):**2.3, 5, 9, 10, 11, 13, 15, 17, 20, 23, 25.**Also... Challenges 2.1, 2.**

Wednesday 2/19: Return Q4. **Friction is a Contact Force Between Two
Surfaces.** The Normal Force is perpendicular to the plane of contact.
Friction is parallel to the plane of contact, and depends on the Normal Force.
**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. Kinetic friction opposes motion and is always
F_{f,k} = µ_{k} F_{n}. Static friction opposes
impending motion and can be zero to a maximum of F_{f,s,max} =
µ_{s}F_{n}. The actual static friction force is just big
enough to keep the object from moving. If you apply a big enough force you (1)
break the static friction barrier, (2) switch to kinetic friction, which is
lower, and (3) the resulting net force means you are accelerating -- you've
switched from Newton's 1st Law to 2nd Law. To move at a constane speed with
kinetic friction, the applied force must equal F_{f,k}. You have to
test to see if static friction holds.

- 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)

Thursday 2/20: **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. Kinetic
friction opposes motion and is always F_{f,k} = µ_{k}
F_{n}. Static friction opposes impending motion and can be zero to a
maximum of F_{f,s,max} = µ_{s}F_{n}. **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.

Friday 2/21: **Friction Problems:** (1) A car moving at 70 mph (31.3 m/s)
on dry concrete (coefficients of friction 1.00 and 0.800) -- find the shortest
stopping distance. To find the distance, we need the acceleration. To find the
acceleration we need to find the net force (F = ma). To find the forces, we
need the sum of forces equations in *x* and *y*, which we get from
the Free Body Diagram. Shortet stopping distance requires maximum static
friction -- if tyhe car is moving to the right, friction must point to the left
to stop. (2) Repeat for the car on sheer ice -- divide the coefficients of
friction by 10 (0.100 and 0.0800) -- where in a panic the cars slides to a
stop. (3) At 70 mph, what is the minimum radius *r* for a circular turn
with a flat road -- in control on dry concrete? -- skidding on ice? For UCM we
need the centripetal acceleration, which we get from the Centriptal Force:
F_{c} = ma_{c} = mv²/r . Quiz 7 is a TWO-PAGE Take-Home on
Friction, due on Wednesday 26 February 2014.

- (1) a
_{x}= -9.81m/s², x = 49.93 m (half a football field + 1 endzone), t = 3.191 sec. (2) x = 624.2 m (over six footnall fields including endzones, about 3/8th of a mile), t = 39.88 sec. (3) r = 99.87 m and r = 1248 m (about ¾ mile). - Of course we bank the turns so that we can add an
*x*-component to the Normal Force to aid in the Centripetal Force. With banking, there is a njatural speed you can safely go around the curve sliding on zero friction. - NOTE: The Centripetal Force F
_{c}does NOT appear in the F.B.D. -- instead something has to CAUSE F_{c}. For Rodney on the string it is the tension in the string. For a car on a flat road it's friction. For a banked curve it's a mix of friction and the*x*-component of the angled Normal Force. - People coming back from Europe and Japan rave about the high speed trains -- up to 200 mph -- that run on time. Why don't we have them here? Simply put -- we've been cheap. Amtrak is required to share track with slower freight lines, except in the Boston-New York-Washington Northeast Corridor, which has been rebuilt for speeds up to 155 mph. To go fast, comfortable and safe, you need smooth and banked (superelevated) tracks. This requires a whole new railroad -- it's like the difference between a country road and an Interstate highway. Europe has invested billions of euros and Japan trillions of yen to build their systems. The Japanese bullet trains entered service in 1964. We went to the moon, encouraged airlines and automobiles, and invested billions bombing Southeast Asia in the 1960s.

Monday 2/24: Return Q5. 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 = ´p / ´t = change in momentum / change in tim*e
instead of *F=ma*, but really the same thing. **Impulse Equation:**
´p = F ´t .**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.

Tuesday 2/25: Return Q6. **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. **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 -- KE = ½mv² -- an energy of motion, always positive,
scalar, no direction information. Momentum is conserved in all collisions, KE
is conserved only in Totally Elastic Collisions. For all other colisions, KE is
lost. The energy goes into damage, heat and noise.

- For the wrecks today, assuming I remember the numbers correctly, Car 1 had
m
_{1}= 1850 kg, v_{1}= 22.5 m/s, so p_{1}= m_{1}v_{1}= 41,600 kg·m/s ; Car 2 had m_{2}= 2350 kg, v_{2}= 19.7 m/s, so p_{2}= m_{2}v_{2}= 46,300 kg·m/s. Total mass of both cars, M = m_{1}+ m_{2}= 4200 kg. The head-on collision left the wreck with speed V = -1.12 m/s ; the rear-end collision had V = 20.93 m/s and the side-impact collision had V = 14.82 m/s and ¸ = 48.1°. **Additional Problems 1.**(Click here for a copy.)**Additional Problems 2.**(Click here for a copy.)

Wednesday 2/26: More on automobile safety systems and how they work to save
your life. What's the opposite of a Totally Inelastic 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). Review for Exam 2.

Thursday 2/27: Exam 2.

Friday 2/28: WMU SPIRIT DAY -- No Classes.

- WMU Spring break next week. Our next class will be Monday 10 March 2014.

SPRING BREAK -- NO CLASSES.

Monday 3/10: **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.** ****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).

- If you have to make up Exam 2, I'd like to try to do these on Tuesday -- you need an hour anywhere from 11-3. See Dr. Phil or email.
- 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?
- 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.
**The Real World (Reminder) (Again.) (Come on, people. I first assigned this on**Go to the Library, the magazine section of a book or grocery store, or a personal collection. Look for automobile magazines like!):*Tuesday 21 JANUARY 2014**Road and Track*,*Car and Driver*, etc. Perhaps about 1/3 of the way in, look for a performance review of a new car with a graph of v vs. t under maximum acceleration conditions on a track. Note how the graph looks, as opposed to our Time Regions I and II in our S-Shaped Curve simplified trip. Do you understand why the real graph looks like it does?**Cosmos: A Spacetime Odyssey**-- Neil Degrasse Tyson revives the groundbreaking science literacy show by Carl Sagan. New episodes Sundays at 9pm on FOX and National Georaphic. Rerun on Modays at 10pm on National Geographic channel.

Tuesday 3/11: 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. **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.).

- On March 14, 2014, the National Geographic Society, in association with the National Aeronautics and Space Administration (NASA), will be presenting its special “Live from Space” at 8 p.m. Eastern Daylight Time (EDT).
**Tuesday Night**Light rain early...then periods of snow overnight. Low near 30F. Winds NNE at 10 to 20 mph. Snow accumulating 1 to 3 inches.**Wednesday**Snow will taper off and end during the morning but skies will remain cloudy during the afternoon. High 29F. Winds N at 15 to 25 mph. 1 to 3 inches of snow expected.**Wednesday Night**A few clouds. Low around 0F. Winds NNW at 10 to 20 mph.

Wednesday 3/12: **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.

- Another Skype lecture due to roads and a cold. Looks like a lot of students couldn't make it in, as well.
- Another round of audio lectures:
- Work and Energy (MP3)
- Conservation of Energy Applications (MP3)

Thursday 3/13: 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 )
**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. 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 in the same time.

- Another Skype lecture due to "just the" cold now.
- Another round of audio lectures:
- Roller Coasters (MP3)
- Elastic Collisions and Power (MP3)
- 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.***Mirror Site:**This week I've had trouble updating the class website. Took me 11 hours yesterday. The Help Desk may have found a solution. But if it should ever happen that you think there should be a class webpage update and you're not seeing it... (1) Try Reloadin the page. Your browser may he using an old copy of the page. (2) I do maintain a mirror site on my own website:- Mirror WMU Homepage: http://www.dr-phil-physics.com/wmu-mirror/index-template.html
- Mirror Class Webpage: http://www.dr-phil-physics.com/wmu-mirror/classes/ph107-27.htm

Friday 3/14: (It's Pi Day!) Return X2. **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? **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). Q8 is a Two-Page Take-Home on
Universal Gravity, Work and Conservation if Energy, due on Wednesday 19 March
2014.

Monday 3/17: Return Q7. 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). **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. **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.

Tuesday 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. 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. **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.

- For our front lab table boat, it's mass-to-volume ratio is 62.50 kg/m³ < 1000 kg/m³, so not only does it float, it is mostly out of the water!
- With a volume of 4.00 m³, at a total mass of 4000 kg, the loaded boat
would have its top level with the water, so essentially it's about to sink.
That translates into 3750 kg of cargo (coal, corn, iPods, passengers, etc.).
Realistically, 2000 kg of cargo, 4400 lbs. on Earth, can be loaded with plaenty
of boat out of the water. NOTE: We will not address
*how*the cargo is loaded -- the boat needs to be reasonably balanced or it will swamp and sink. - With the mass of the water displaced by the boat equalling the mass of the
boat, and the volume of the water displaced = the volume of the submerged part
of the boat, we can use the mass-to-volume ratio of the water to find the
volume, the length and width dimensions of the rectangular boat can be used to
find
*h*, the depth of the submerged part of the boat. For our lab desk in water, this is*h = 0.06250 m = 6.250 cm*. - 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.

Wednesday 3/19: 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. **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. **How to get liquid out of a cup using a
straw** -- or why *Physics does not "suck"*, but pushes using
a pressure difference.

- SCUBA = Self-Contained Underwater Breathing Apparatus -- invented by the famous Jacques Cousteau in WW II.
- BTW -- It's nice to know people are reading their Topic 1 books. But obviously reading it during class by holding it in front of your face is really rather rude and/or passive-agressive..

Thursday 3/20: **Absolute **(total) Pressure vs. **Gauge** Pressure
(difference between two readings). 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**.
**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.

- NCAA March Madness -- #14 WESTERN MICHIGAN UNIVERSITY vs #3 Syracuse, 2:45pm.
- Alas... 77-53.
- 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.
- 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.
**Problems Chapter 4:**1, 5, 7, 13, 17, 27, 28.**Additional Problems 3-4.**(Click here for a copy.)

Friday 3/21: Bernoulli's Equation. The
Water Tower and the Faucet Problem. Why the
water tower needs a vent. The Continuity
Equation. Want Smooth Continuous Flow, not Turbulent Flow or Viscous Flow.
*Flow rate = Volume / time = Cross-sectional Area × Speed*. Topic 2
Worksheets (Click here for 1st
Worksheet and Directions) Q9 Take-Home Quiz on Mass-to-Volume Ratio and
Bernoulli's Equation, due Wednesday 26 March 2014.

- 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)
- And Safety First! Do not try to write data down on Worksheet 1 while you are driving!

Monday 3/24: 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
(*F _{drag} = -bv *) and high speed (

- Those low and high speed drag constants,
*b*and*c*, contain a lot of Physics -- based on shape of object, roughness of surface, composition od atmosphere its passing through, etc. Which equation do we use? Well, low speed drag is traveling slow and high speed if traveling fast...*see tomorrow's lecture!* - 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.

Tuesday 3/25: **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.

Wednesday 3/26: **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).

- Note that (1) Hot and Cold are relative terms and (2) Heat in Physics means Heat Energy -- there is no Cold, just less Heat.

Thursday 3/27: 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. 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.

Friday 3/28: Review Exam 3 topics. (See below.) **Problems:** A gas tank
is filled when the temperature is around 0°F (-20.0°C). The
temperature then rises to 68°F (+20.0°C). For the tank, V_{0}
= 20.0 gal. and α_{steel} = 12.0 × 10^{-6}
°C^{-1}. For the gasoline, V_{0} = 19.0 gal. and
β_{gasoline} = 950. × 10^{-6} °C^{-1}.
Find the new volume of the tank. Find the new volume of the gasoline.
What about the air in the tank? It's original volume was 20.0 gal - 19.0 gal =
1.00 gal and it's initial pressue is 1.00 atm (101,300 Pa). But air is a gas --
it's compressible. We need... **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. Q10
Take-Home on Length & Volume Expansion and the Ideal Gas Law, due on
Wednesday 2 April 2014. *To be clear, parts (c) and (d) are different ways of
calculating the same thing.*

Exam 3 Topics:Leftover from Sample Exam 2:== Work, KE, PE, Conservation of Energy == Newton's Law of Universal GravityCurrent topics:== Mass-to-volume ratio (density) == Floating and displacement == Pressure = Force / Area == Pressure due to a column of liquid == Bernoulli's Law == Continuity Equation == Length and Volume Expansion == Simplified Ideal Gas LawNext topics:>> Heat capacity and energy to change phases (This material will NOT be covered in Spring 2014 and will NOT be on Exam 3.) == Heat engines and efficiencies (This material WILL be covered on Monday and Tuesday and WILL be on Exam 3. It will also be used on Worksheet 4 for Topic 2.) >> Sound, wavelengths, resonance and interference (This material WILL be covered and WILL appear on the Final Exam. It will NOT be on Exam 3.)

Monday 3/31: **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).

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

Tuesday 4/1: The Heat Engine and
Three Efficiencies (Actual, Carnot and 2nd
Law). Power is Work per time. We talk of Useful Work, Total Energy, Waste
Energy -- we can substitute the rate work is done, power, for Useful Power,
Total Power, Waste Power. **Example:** It takes 15 to 50 h.p. from your
car's engine to maintain highway speed due to air resistance and friction. 15
h.p. × 746 W/h.p. = 11,190 W = 11,190 J/s . This is the useful power. Each
second, the useful work is W = 11,190 J. Assume the hot reservoir is
T_{H} = 850.°C and the cold reservoir is T_{C} =
95.0°C. This allows us to find the Carnot effiiciency. If, for the
purposes of simplicity, we take the 2nd Law efficiency as 100%, then the Carnot
efficiency = Actual efficiency. This allows us to find the Total energy,
Q_{H} , and the waste heat, Q_{C} .**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 -- there is not much room between the actual efficiency
and the Carnot efficiency to make an 8- to 10-fold increase in m.p.g. To use
less fuel, do less work.

- The actual efficiency of a real heat engine 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}.

Wednesday 4/2: What happens if we reverse the arrows in the Heat Engine
diagram? We get a **refrigerator**. 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 .

**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.- Remember, the wave is a disturbance that moves through the medium (material). The actual motion of the material is local and small.
- Magnitude 8.1 earthquake off the coast of Chile. A tsunami is a "one-off", a single pulse wave.

Thursday 4/3: Review.

**Reminder:**First day to turn in Topic 1 Paper is Thursday 10 April, you can also turn it in on Friday 11 April and Monday 14 April 2014. The last day to turn a Draft paper in if you either (a) wish to turn in a draft or (b)__must__turn in a draft if you're reading a book not on the booklist but approved by Dr. Phil.

Friday 4/4: Exam 3.

Exam 3 Topics:Leftover from Sample Exam 2:== Work, KE, PE, Conservation of Energy == Newton's Law of Universal GravityCurrent topics:== Mass-to-volume ratio (density) == Floating and displacement == Pressure = Force / Area == Pressure due to a column of liquid == Bernoulli's Law == Continuity Equation == Length and Volume Expansion == Simplified Ideal Gas LawNext topics:>> Heat capacity and energy to change phases (This material will NOT be covered in Spring 2014 and will NOT be on Exam 3.) == Heat engines and efficiencies (This material WILL be covered on Monday and Tuesday and WILL be on Exam 3. It will also be used on Worksheet 4 for Topic 2.) >> Sound, wavelengths, resonance and interference (This material WILL be covered and WILL appear on the Final Exam. It will NOT be on Exam 3.)

Monday 4/7: 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 .** Demonstration**: the Slinky shows
both longintudinal (string type) and transverse waves (sound type). **Waves
and Resonance. **Standing Waves on a
string. Fundamental, First Overtone, Second Overtone, etc.
**Demonstration**: First and higher overtones on a string driven by a saber
saw. We are varying the speed of the wave by changing the tension. With a fixed
frequency from the saber saw, this changes the wavelength. (Can't see the
Fundamental on the saber saw demo, because the tension required usually breaks
the string.) Standing Waves in a
tube. Topic 2 Worksheets 2-4 (Click here for all 4 Worksheets and Directions)

- Beginning Monday, April 8, the Course/Instructor Evaluation System (ICES Online) will open to students for the spring 2013 administration. (via GoWMU)
- If you missed Exam 3 on Friday 4 April 2014, I'd like to try to do these on Tuesday -- you need an hour anywhere from 11-3. See Dr. Phil or email.
- 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 10 April 2014, (2) Friday 11 April 2014 or (3) Monday 14 April 2014. 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!

Tuesday 4/8: 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. 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} |* .

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

Wednesday 4/9: **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} |* .

Thursday 4/10: **dB = decibel**, a logarhythmic scale. A change in
±3 dB is twice or half the sound intensity, while a change in ±10dB
is a factor to ten. (log(2) = 0.3, move the decimal place get 3, log(10) = 1,
move the decimal place get 10.) Signal-to-noise ratio: How much louder the
sound (signal) you want is over the background hiss (noise). **Example:** A
good CD player is advertised as having a signal-to-noise ratio of 96dB. What
does this mean? 10^{9} = 1,000,000,000, move the decimal place get 90.
Breaking up our dB into pieces, 96dB = 90dB + 3dB + 3dB, represents
1,000,000,000 × 2 × 2 = 4,000,000,000. So a 96dB range represents a 4
billion times difference between the signal and the background noise! O&B
p. 250 -- Table of sound levels. **The speed of sound in air.** Sonic Booms
and other shockwaves. First Day to turn in
Topic 1 paper.

- Logs were invented to (1) allow us to plot things of very great size difference, (2) change multiplication (and division) into addition (and subtraction) -- this last point was very important in the days before calculators.
- (There's a third reason, having to with turning graphs with curves intographs with straight lines, but we shan't worry about that here.)
- 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.*

Friday 4/11: Problems: (1) A lightning bolt strikes 1 mile = 1609 m away. The flash travels at the speed of light, c = 300,000,000 m/s, the sound at 68°F = 20°C, travels at 344 m/s. v = d / t, so t = d / v. 5.363 millionths of a second for light and 4.677 seconds for sound. (2) An empty Coke resonantes with its fundamental (pipe open at one end and closed at the other). L = 25.0 cm = 0.250 m. λ / 4 = L, λ = 4 L = 1.000 m . v = f λ , f = v / λ = 344 Hz. The sound wave comes from a vibrating string, fixed at both ends, vibrating at the same frequency f. λ / 2 = L , λ = 2 L, so if L = 80.0 cm = 0.800 m, then λ = 1.600 m. The wave speed in the string, which has nothing to do with the wave speed in air, is v = f λ = 550.4 m/s. (3) Sound A is 65dB. Sound B is 80 times louder. 80 = 10 × 2 ×2 × 2, which translates to 10dB + 3dB + 3dB + 3dB = 19dB. So Sound B is 65dB + 19dB = 84dB. Second Day to turn in Topic 1 paper.

- As a kid you may have been taught to count One-Mississippi-Two-Mississippi... when lightning flashes. Every five seconds is one mile, which matches our calculations above.
- One of the sample finals has a problem about the launch of a Saturn V rocket, the kind that sent us to the Moon. You are given the engine thrust and the rocket weight. To find the initial acceleration, you just don't do F = m a. Remember vectors -- Free Body Diagram, Sum of Forces equation, and the NET force uses F = m a.

Monday 4/14: Return X3. 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 **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. Third Day
to turn in Topic 1 paper.

- The Student Evaluation system (ICES) is now open for you. See the link at the top of this page.
- NOTE: X3A prob. (2a) and X3B prob. (2c) -- solution has a minor error. It doesn't change the answer, just the subscripts in the first equation. I added an extra step to make it clear. If you think it affects your score, please bring it by!\

Tuesday 4/15: 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 (!!!). 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.

- Remember Topic 2 Worksheets due Thursday!

Wednesday 4/16:

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.
- Topic 2 Worksheets due Thursday!

In case you suddenly realize you need data for Topic 2: 1996 T-10 Chevy 4WD Blazer 4300 lbs., 185 hp 0 to 45 mph in 12 seconds Trip and Gas Run Together: 313,895.3 to 314179.6 7:33am to 9:15am (stops of 10 min + 20 min) 2:50pm to 4:30pm (stop of 7 min) 7:34am to 9:30pm (stops of 7 min + 20 min) 4:55pm to 6:30pm (stop of 7 min) gas at 2nd fill: 15.83 gallons Dr. Phil

Thursday 4/17: **"A Taste of Modern Physics"** -- goes to
size/time/length scales far outside our normal experience. The point of today's
lecture is to give you a taste for how strange things get in the real world.
**Quantum Mechanics**. *... the Bohr Atom (derivation on the reverse side
Dr. Phil's Periodic Table) to see how
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, 1110 Rood,
the electron cannot exist at just any energy level or radius from the nucleus).
In effect, the allowed electron orbitals in the Bohr Atom are standing waves
set on a circular string. (ooh!) The deBroglie wavelength -- Wave/Particle
Duality for Matter. Planck's constant -- a very small number, but it is NOT
zero ( h = Planck's constant = 6.626 × 10 ^{
-34} J·sec , h = 0 in Classical Physics). So the deBroglie
wavelength only matters for very small objects, not Buicks. For an electron to
move from one orbit to another, it must gain or lose energy. Going from a
higher n to a lower n, the difference in the energy is release as a photon with
E = hf. To go from a lower n to a higher n, the electron has to absorb a photon
of E=hf. And now we have an explanation of the spectral lines which we had once
described as "fingerprints for elements". Burn hydrogen and the light
emitted, when run through a prism will split not into a rainbow, but individual
lines of individual colors -- these are emission lines. Take white sunlight,
shine it through a prism and look at the rainbow of colors under a microscope
and you will see that individual lines of color are missing -- these are
absoption lines caused by the hydrogen gas in the Sun's atmosphere removing
those colors and moving their electrons to higher orbits or ionizing
completely.*

- The course is now closed for Spring 2014.
- If there is anything you need to turn in -- T1 book report, T2 worksheets, etc. -- you MUST get it turned into the office by Friday 25 April 2014 for Dr. Phil to see it before finishing grades. Similarly, if there are any Exams you have to make up, the last day to do this is Friday 25 April 2014, so arrange something with Dr. Phil.
- Finals Week Office Hours are now posted.
- NOTE For Q12: People often forget to use their 1/x key on their calculator
when finding R
_{eq}for Parallel resistors. 1/R_{eq}= 1/R_{1}+ 1/R_{2}... There is an alternate equation ONLY if you have hust TWO resistors in Parallel: R_{eq}= ( R_{1}R_{2}) / (R_{1}+ R_{2}).

Friday 4/18: THE LAST CLASS.