Dr. Phil's Home

Lectures in PHYS-1070 (20)

Updated: 1 July 2007 Sunday.

Final Course Grades and Breakdown by Category 7/1/2007 Sunday 

Week of 25-29 June, 2007.

Monday 6/25: LAST CLASS. A brief look at Modern Physics, including Special & General Relativity, deBroglie wavelength, Heissenberg Uncertainty Principle, and Atomic and Nuclear Physics. ... 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 = 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. Handouts: Dr. Phil's Periodic Table and From UCM to Spectral Photons. A short Course Review, using the first of the Sample Final Exams. Q22 in-class attendance sheet.

Q23 (The Last Quiz) is used as a Check-Out Form at the Final Exam (Tuesday 26 June 2007, 2:00-4:00pm, Be There!), so the points are really a "freebie". That means no more quizzes for the semester. You're welcome.

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.

Tuesday 6/26: Final Exam (2:00-4:00pm)

Wednesday 6/27: Office Hours Noon to 3pm.

Thursday 6/28: No Office Hours.

Friday 6/29: Office Hours Noon to 3pm.

Monday 7/2: Office Hours Noon to 3pm. (tentative)

Tuesday 7/3: Final Grades will be done by Noon.

 


Week of May 7-11, 2007.

Monday 5/7: Class begins. The nature of studying Physics. Science education in the United States. Natural Philosophy. The Circle of Physics. Aristotle and the Greek Philosophers. Observation vs. Experiment - Dropping the book and the piece of paper (2 views). Distribute syllabus.

Tuesday 5/8: Mechanics is the study of motion. So what is motion? Zeno of Elea -- Zeno's Paradoxes. "Speed Limit 70" First Equation: Speed = Distance / Time. Development of Speed equation for Constant or Average Speed. delta-x = xf - xi , x = x0 + v t . Topic 1 assigned. (Searchable booklist available online here --or-- the entire handout in .pdf format here.)

Wednesday 5/9: No class.

Thursday 5/10: SI Metric System. 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. 60 m.p.h. = 26.8 m/s. 1.00 m/s = slow walking speed. 10.0 m/s = World Class sprint speed (World Record in 100m dash -- 9.76 seconds -- Sat. 13 May 2006). Dr. Phil's Reasonable Significant Figures. 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 × 1012 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.) A simplified trip to the store -- The S-Shaped Curve. Acceleration. (SI units m/s²) 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 Monday 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). Q1 and your PID number. (If you missed class on this day, check with Dr. Phil sometime soon.)

Friday 5/11: Finding the set of Kinematic Equations for constant acceleration. Kinematic Equations for Constant Acceleration. The Equation Without Time -- Avoiding the Quadradic Formula. Finishing The S-Shaped Curve: plotting x-vs-t gives straight line in Region II, but parabolic curves for Regions I and III. Look at real world v-vs-t graphs in a car magazine. The line is curved, not straight and has small hiccoughs. The variable for change in acceleration is called "jerk" (SI units m/s³), and you can feel it as a jerk. To aid in setting up problems with the kinematic equations, you might try to list all six kinematic variables (x0, x, v0, v, a and t) and give the values for those you know, those you don't know and those you want to find out. This will help you choose which kinematic equation(s) you'll need. What do we mean by a = 1 meter/sec² ? You cannot accelerate at 1 m/s² for very long. Types of Motion: No Motion (v=0, a=0), Uniform Motion (v=constant, a=0), Constant Acceleration (a=constant). We generally cannot accelerate for very long. 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. First set of Sample Exam 1's handed out. (Click here and here for a copy.) Q2 in-class quiz.

Week of May 14-18, 2007.

Monday 5/14: 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. The P-O-R (Press-On-Regardless) road rally problem. "You can't average averages." Free-Fall: If we ignore air resistance, all objects near the surface of the Earth fall towards the Earth at the same rate. ay = -g ; g = 9.81 m/s². That's nearly ten times the acceleration a = 1 m/s² we talked about yesterday. Rewriting the Kinematic Equations for motion in the y-direction, pre-loading them for free-fall. The consequences of Falling Down... ...and Falling Up. The Turning Point ( vy = 0, but ay = -g during whole flight). The illusion of "hanging up there in the air" at the turning point. 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. SOHCAHTOA. Second set of Sample Exam 1's handed out. (Click here and here for a copy.) Q3 Take-Home quiz, due Tuesday 15 May 2007 in class or by 5pm, though we may extend the deadline into Wednesday.

Tuesday 5/15: 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. For studying, find vector D = vector A - vector B, where in class you were given vector A = 5.00 m @ 30° and vector B = 7.00 m @ 120° . Finding the final vector velocity of The guy with the fedora and the cigar problem. Third set of Sample Exam 1's handed out. (Click here and here for a copy.) Q4 Take-Home quiz, due Thursday 17 May 2007 in class or by 5pm. Read the quiz carefully. Part (d) is to look at how far the ball falls from the turning point in ¼T -- this is that region near the turning point we discussed for the Michael Jordan "defying gravity" illusion.

Wednesday 5/16: No class.

Thursday 5/17: Two Dangerous Equations. You can only use the Range Equation if the Launch Height = Landing Height. But the sin (2*theta) 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° - theta) that gives the same range (but a different time and height). High and low trajectories for Range Equation. Types of Motion studied so far: No motion, Uniform motion (v=constant, a=0), Constant Acceleration. 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. ac = v²/r. Space Shuttle in Low-Earth Orbit. (There's still gravity up there!) Q5 Take-Home quiz, due Tuesday 22 May 2007 in class or by 5pm.

Friday 5/18: Exam 1.

Week of May 21-25, 2007.

Monday 5/21: Demo: Rodney Reindeer and U.C.M. 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. 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. Using Vector Addition for Velocities: Upstream, downstream (rivers), Headwind, tailwind, crosswind (airplanes). 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. 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.) Q6 Take-Home quiz, due Thursday 24 May 2007 in class or by 5pm.

Tuesday 5/22: Newton's 3 Laws continued. 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.). 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. Sum of forces in x or y equations -- either will be equal to 0 (Newton's 1st Law) or ma (Newton's 2nd Law). Example of 125 kg crate being dragged/pushed around. Variations as we allow for an applied force that it at an angle. "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. For the problem in class, we had a sign with m = 15.0 kg and two tension forces, T1-vector = 107.7 N @ 150° and T2-vector = 131.9 N @ 45°. You can check to make sure these forces cancel in the x-direction and support the weight of the sign in the y-direction. Discussion of "two pound test fishing line", stretching and breaking of cables, Safety Factors. Hand out first sample exam pages for Exam 2. (Click here and here for a copy.) Q5 deadline extended to Thursday 24 May 2007 in class. Q7 Take-Home quiz, due Friday 25 May 2007 in class or by 5pm.

NOTE: If you are keeping score, you'll realize that we are in Chapter 2 of your textbook. Though I continue to do some things different from the text, you should read through Chapter 1 and the parts of Chapter 2 we've already covered. My intent is to use the textbooks as "a second voice" -- a different way of explaining things than I give you in class. This can be very useful to either (a) see a different way of looking at the class material or (b) suddenly say to yourself, "Hey, I understand what that means!" From now on, the textbook will be increasingly more useful.

Wednesday 5/23: No class.

Thursday 5/24: Return X1. (Click here for a solution.) 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. 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. 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. Two kinds of Friction: Static (stationary) and Kinetic (sliding). For any given contact surface, there are two coefficients of friction, µ, one for static (µs) and one for kinetic (µk). Static is always greater than kinetic. Second set of Sample Exam 2's handed out. (Click here and here for a copy.)

Friday 5/25: Static & Kinetic Friction. 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. 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 = change in momentum / change in time 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. Topic 2 Worksheet 1 (Click here for a copy and directions.) Q8 in-class quiz. Q9 Take-Home quiz, due Tuesday 29 May 2007 in class or by 5pm.

Week of May 28-June 1, 2007.

Monday 5/28: MEMORIAL DAY. No classes.

Tuesday 5/29: Linear momentum is conserved in all types of collisions . Totally Inelastic Collisions. Examples: 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. What happens in a wreck. How airbags work. Note: We do NOT want our cars to have Totally Elastic Collisions -- the whiplash on our fragile bodies would be awful. Instead, our cars are designed to crumple and "die" for us. Kinetic Energy -- an energy of motion, always positive, scalar, no direction information. Kinetic Energy is NOT conserved in an inelastic collision. Totally Elastic Collisions. Close approximations: The Executive Time Waster. Why you want inelastics collisions in a wreck. 5 mph versus 3 mph impact bumpers. "Adobe: The Little Car Made of Clay". Exam 2 moved from Friday 1 June 2007 to Monday 4 June 2007. Third set of Sample Exam 2's handed out. (Click here for a copy.) Q9 deadline extended to Thursday 31 May 2007. Q10 Take-Home quiz, due Thursday 31 May 2007 in class or by 5pm.

Wednesday 5/30: No class.

Thursday 5/31: 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). Work = Energy. 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. Continue with 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. Q9 and Q10 deadlines extended to Friday 1 June 2007. Q11 Take-Home quiz, due Friday 1 June 2007 in class or by 5pm.

Friday 6/1: Normal class today. Exam 2 moved to Monday 4 June 2007. What's the opposite of a collision? An explosion. Or recoil. Example: A pitcher on ice skates at rest -- when he hurls a fastball to the right, he goes to the left. Total momentum of the system remains constant (in this case, zero). Conservation of T.M.E. (P.E. + K.E.) 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.) The Ballistic Pendulum -- We can find the speed of a projectile through an Inelastic Collision followed by Conservation of TME. 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. World's Record Free-Fall. UCM Revisited. Centripetal Force, Fc = m ac. Something has to cause the centripetal force, so it goes on the "ma" side of the sum of forces equation, because centripetal force by itself doesn't appear on the F.B.D. No such thing as Centrifugal Force. Only the Centrepital Force, which points radial inward, just like the centripetal acceleration. You aren't forced to the outside, you merely move in a straight line unless there is a force to keep you on the circle. Test tube example. How you could "get thrown clear of the wreck" in the old days. The story of the 50,000 rpm Ultra-Centrifuge and the Fresh Rat's Liver. Q12 in-class quiz. For Exam 2: NO Newton's Law of Universal Gravity, NO artificial gravity in rotating space stations.

Week of 4-8 June, 2007.

Monday 6/4: Exam 2.

Tuesday 6/5: Newton's Universal Law of Gravity (or Newton's Law of Universal Gravity). Takes two masses -- there are two forces, according to Newton's Third Law. Finding g. (Off by 1/2 %, because Earth is not a uniform, homogeneous sphere.) Tides (high/low, spring/neap). 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. 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). Up until now, our objects really haven't had any dimensions. 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. Floating on the Surface: Mass-to-Volume Ratio of the boat < Mass-to-Volume Ratio of the Liquid. Topic 2 Worksheets (Click here for remaining Worksheets and Directions) Q13 Take-Home quiz, due Thursday 7 June 2007 in class or by 5pm.

Wednesday 6/6: No class.

Thursday 6/7: Return X2. (Click here for a solution.) 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. Calulating the amount of the boat submerged, by using the fact that the mass of the boat and the displaced water are the same. First set of Sample Exam 3's (Click here and here for a copy.) Q13 deadline extended to Friday 8 June 2007. Q14 Take-Home quiz, due Monday 11 June 2007 in class or by 5pm.

Friday 6/8: Archimedes and Eureka! (I found it!) 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. The perils of SCUBA diving. Smooth Fluid Flow. Bernoulli's Equation and the Continuity Equation. Water Tower and the Faucet Problem. Why the water tower needs a vent.

JUST FOR FUN: In PHYS-1070 we talk about so many topics and Dr. Phil often talks about "systems" and how they interact -- so it's no surprise that this video on YouTube that I discovered last semester is "just plain fun" on so many levels: http://www.youtube.com/watch?v=lBvaHZIrt0o. Enjoy.

Week of 11-15 June, 2007.

Monday 6/11: Bernoulli continued. 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.) 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). Linear Expansion: Most objects expand when heated, shrink when cooled. Length Expansion. Volume Expansion of Solids and Liquids. Second set of Sample Exam 3's (Click here and here and here for a copy.) Q14 deadline extended to Tuesday 12 June 2007.

Tuesday 6/12: 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. I-57 in Chicago and the expanding asphault. 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. Ideal Gas Law (PV/T = constant). The Laws of Thermodynamics. Heat Energy (Q). 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. Q15 Take-Home quiz, due Thursday 14 June 2007 in class or by 5pm.

Wednesday 6/13: No class.

Thursday 6/14: Reverse the arrows in the Heat Engine and you get a Refrigerator. 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. 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. Wave speed = frequency x wavelength. 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. Standing Waves in a tube. Q16 Take-Home quiz, due Friday 15 June 2007 in class or by 5pm. Q17 will be an in-class quiz on Friday 15 June 2007, on the resonance of a standing wave for a string fixed at both ends (Fundamental, 1st Overtone, 2nd Overtone).

Friday 6/15: Normal class today. Exam 3 moved to Monday 18 June 2007. Tuning forks, resonance boxes. The range of "normal" human hearing: 20Hz-20,000Hz (10 octaves). Tuning forks, resonance tubes. Beat frequency. Constructive and Destructive Interference. Acoustics of concert halls. Artilleryman's ear -- mid-range hearing loss. dB = decibel, a logarhythmic scale. The speed of sound in air: 334 m/s @ 0°C and 344 m/s @ 20°C. Takes time for sound to travel. Q17 in-class quiz.

NOTE: The heat energy Q needed to change the temperature or phase of a material (specific heat, heat capacity, latent heats) will not be on Exam 3.

Week of 18-22 June, 2007.

Monday 6/18: Exam 3. Last day to turn in Topic 1 book reports.

Tuesday 6/19: The Realization that Electricity and Magnetism were part of the same Electromagnetic Force was a great triumph of 19th century physics. Demo: Static electricity. 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. 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. First set of Sample Final Exams. (Click here and here for a copy.) Q18 Take-Home quiz, due Thursday 21 June 2007 in class or by 5pm.

Wednesday 6/20: No class.

Thursday 6/21: How does q1 know that q2 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 FE = q E (Electric Force = charge times E-field the charge is emersed in). Maximum E-field in air, E-max. Electric Potential (Voltage). Spark gaps. Voltage can be measured, then used to find strength of E-field. SI units: E-field is (N/C) or (V/m) - both work. Charges tend to accumulate on long pointy things, which explains why church steeples get hit by lightning. Or why it's your fingertips which can get shocked when reaching for the light switch after walking on carpet in the wintertme. 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. and A.C. circuits. Ohm's Law. V=IR form. (Ohm's "3 Laws"). 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"). The Simplest Circuit: Battery, wires, load (resistor). Series and Parallel Resistors. Discussion of Significant Figures again. 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 set of Sample Final Exams -- the All-Titanic Exam. (Click here for a copy.) Q19 is a Take-Home quiz, handed out Thursday 21 June 2007, due Friday 22 June 2007 in class or by 5pm.

Friday 6/22: Resistor Network Reduction. Having reduced the resistor network to a single equivalent resistance, go back and fill in the table for V = I R and then P = I V. Resistor R1 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.) 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). Frequencies HIGHER and wavelengths SHORTER than visible light (UV ultraviolet, X-rays, Gamma rays). 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. So use X-rays. Why Superman's X-ray vision cannot work -- because everyday situations are "dark" in the X-ray band, thankfully! Frequences LOWER and wavelengths LONGER than visible light (IR infrared, Microwave, Radio waves, ELF extremely low frequency). Optics: Optics: Geometric Optics (empirical) and Physical Optics (more wave and fieldlike). Ray Tracing: Rays from a spherical source become essentially parallel rays when you are far away. When a straight light ray hits a boundary between one material and another, three things can happen: Reflection, Absorption, Transmission. The Law of Reflection. The Optical Lever -- move a mirror by 10° and the reflected ray moves by 20°. (Dr. Phil's theory on the origin of "seven years of bad luck for breaking a mirror".) When light rays strike a rough surface, you get Scattering, which is reflections off many different angles. People tend to not like photographs of themselves, because they are used to seeing their mirror image -- their normal image, which the rest of us sees, looks "wrong". 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.) If going from an high index of refraction media to a lower index media ONLY, have 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. Topic 2 Worksheets due. Third set of Sample Final Exams, two complete Finals. (Click here and here for a copy.)Q20-21 is a Double Take-Home quiz, due Monday 25 June 2007 in class or by 5pm.