Dr. Phil's Home

## Lectures in PHYS-1070 (19)

Updated: 1 May 2007 Tuesday.

### Week of April 23-27, 2007.

Tuesday 4/24: FINAL EXAM (10:15am-12:15pm)

Tuesday 5/1: Final Grades turned in.

### Week of January 8-12, 2007.

Monday 1/8: Class begins. The nature of studying Physics. Science education in the United States. Natural Philosophy. The Circle of Physics. "Speed Limit 70".

Tuesday 1/9: Speed = Distance / Time. Development of Speed equation for Constant or Average Speed. What do we mean by Measurements? "Units will save your life."

Wednesday 1/10: Continue development of Speed equation. delta-x = xf - xi , x = x0 + v t . Aristotle and the Greek Philosophers. Zeno of Elea -- Zeno's Paradoxes. SI Metric System.

Thursday 1/11: Distribute syllabus. Topic 1 assigned. (Searchable booklist available online here --or-- the entire handout in .pdf format here.) Q1 in-class -- this will be a form and not require any Physics. (will do on Tuesday 1/16)

Friday 1/12: PHYS-1070 Does NOT Meet This Friday.

### Week of January 15-19, 2007.

Monday 1/15: MLK Day to Honor Dr. Martin Luther King, Jr. -- Classes Do Not Meet at WMU -- University-wide activities.

Tuesday 1/16: Aristotle and the Greek Philosophers. Observation vs. Experiment - Dropping the book and the piece of paper (2 views). 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). Q1 in-class form -- does not require any Physics. (leftover from last Thursday)

Wednesday 1/17: Speed. 60 m.p.h. = "A Mile A Minute". (1848: The Antelope) 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.) Q2 in-class quiz.

Thursday 1/18: A simplified trip to the store -- The S-Shaped Curve. Acceleration. Finding the set of Kinematic Equations for constant acceleration. 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 (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. 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). Hand out replacement pages for the Syllabus (pp. 1-4, 13) to reflect the change in Friday and Exam dates for Exam 3. Q3 Take-Home, due Tuesday 23 January 2007. (Click here for a copy.)

Friday 1/19: PHYS-1070 Does NOT Meet This Friday.

### Week of January 22-26, 2007.

Monday 1/22: Example from Thursday -- we found the final position x by using the 1st Kinematic Equation. Now we find x using the 4th Kinematic Equation, "the equation without time" and get the same result. Same Physics, must get same answer. 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. 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.

Tuesday 1/23: 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. Example: Falling off a ten-foot roof (3.00 meters). The consequences of Falling Down... ...and Falling Up. The Turning Point ( v=0 but a = -g during whole flight). First set of Sample Exam 1's handed out. (Click here and here for a copy.) Q4 Take-Home, due Thursday 25 January 2007.

Wednesday 1/24: The illusion of "hanging up there in the air" at the turning point. 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. Example: The guy with the fedora and the cigar problem.

Thursday 1/25: (Dr. Phil was a couple of minutes late getting to WMU this morning -- my apologies for the unavoidable delay.) 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. Adding and subtracting vectors: Analytical method. (Check to make sure your calculator is set for Degrees mode. Try cos 45° = sin 45° = 0.7071) NOTE: We have not quite finished with this section, but you can start the take-home quiz. Second set of Sample Exam 1's handed out. (Click here and here for a copy.) (NOTE: There are two additional complete Exam 1's with solutions available on the class homepage.) Q5 Take-Home, due Wednesday 31 January 2007.

Friday 1/26: PHYS-1070 Does NOT Meet This Friday.

NOTE: Exam 1 is scheduled for FRIDAY 2 FEBRUARY 2007.

### Week of January 29-February 2, 2007

Tuesday 1/30: (Dr. Phil was a few minutes late this morning, weather + garage door wouldn't open (!!!).) Finding the final vector velocity of The guy with the fedora and the cigar problem. Classical/Galilean/Newtonian Relativity: Two observers may see something different. A person on a train tosses a ball straight up. A person watching the train go by see the same ball arc through the air in a parabola. Using Vector Addition for Velocities: Upstream, downstream (rivers), Headwind, tailwind, crosswind (airplanes).

Wednesday 1/31: 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. Third set of Sample Exam 1's handed out. (Click here and here for a copy.)

Thursday 2/1: Classic Simple Pursuit (Cop and the Speeder). Starting from rest, the contant accelerating cop ends up with a final speed twice that of the uniform motion speeder -- because they both have to have the same average speed (same place, same time). There are two times when they are in the same place and the same time -- the other solution is at t=0. Q6 in-class quiz.

Friday 2/2: Exam 1.

### Week of February 5-9, 2007.

Monday 2/5: Snow Day. WMU Closed. No Class.

Tuesday 2/6: 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!)

Wednesday 2/7: 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. 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.) Q7 Take-Home due Thursday 8 February 2007, though you can still turn it in on Monday (due to a webserver problem).

Thursday 2/8: Return X1. (Click here for a solution). Force and Newton's Three Laws of Motion (con't.) 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.). SI unit of force: Newton (N) = (kg·m/s²). Force is a vector. Free Body Diagrams. Normal Force (Normal = Perpendicular to plane of contact). 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. Q8 Take-Home quiz due Tuesday 13 February 2007.

Friday 2/9: PHYS-1070 Does NOT Meet This Friday.

### Week of February 12-16, 2007.

Monday 2/12: 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. Example of 125 kg crate being dragged/pushed around. Simplified universe, without friction. 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."

Tuesday 2/13: Mechanical advantage: multiple pulleys allow us to distribute the net force across multiple cables or the same cable loop around multiple times. Tension in the cable is reduced, but you have to pull more cable to move the crate. Hanging a sign with angled wires -- still the same procedure: Sketch of the problem, Free Body Diagram, Sum of Forces equations in the x- and y-directions, solve for unknowns. Discussion of "two pound test fishing line", stretching and breaking of cables, Safety Factors. Q9 Take-Home due Thursday 15 February 2007.

Wednesday 2/14: 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 and one for kinetic. Static is always greater than kinetic. 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 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").

Thursday 2/15: 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. 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. 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. First set of Sample Exam 2's handed out. (Click here and here for a copy.) Q10 Take-Home due Tuesday 20 February 2007.

NOTE: Q9 is due by 5pm on Thursday 15 February 2007, but you can still turn it in on Friday to the Physics Dept. Office on the ground floor of Everett Tower. (You're welcome.)

Friday 2/16: PHYS-1070 Does NOT Meet This Friday. (NOTE: We DO Meet next Friday 23 February 2007 for a normal class, with Exam 2 the following Thursday 1 March 2007.)

### Week of February 19-23, 2007.

Monday 2/19: Static friction opposes the direction of impending motion and can vary in magnitude from zero to its maximum value. 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"). 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. Head-on Collisions.

Tuesday 2/20: Totally Inelastic Collisions. Example: The Yugo and the Cement Truck with numbers. 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.) Rear-end Collisions. Set up for the Side Impact (vector) collision. What happens in a wreck. Seatbelts and shoulder belts. Second set of Sample Exam 2's handed out. (Click here and here for a copy.) Q11 Take-Home, due FRIDAY 23 February 2007.

Wednesday 2/21: 2-D collisions (side impact). What happens in a wreck. How airbags work. 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).

Thursday 2/22: 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.). 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.

Friday 2/23: This Friday was a normal class, with Exam 2 the following Thursday 1 March 2007. Conservation of Total Mechanical Energy (T.M.E. = K.E. + P.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.) Elastic collisions -- conserve both momentum and K.E. Totally Elastic Collisions. Close approximations: The Executive Time Waste. Why you want inelastics collisions in a wreck. 5 mph versus 3 mph impact bumpers. "Adobe: The Little Car Made of Clay". Some examples of Force problems, setting up Free Body Diagrams, writing the Sum of Forces equations and solving them. Third set of Sample Exam 2's handed out. (Click here for a copy.) Q12 Take-Home, due Tuesday 27 February 2007.

### Week of February 26-March 2, 2007.

Monday 2/26: Class canceled by Dr. Phil due to weather conditions and power failure. Sorry for the inconvenience.

Tuesday 2/27: 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. Although a loop-the-loop is not a proper UCM problem, we can apply UCM at the top of the loop and determine the minimum safe speed for going around the loop without falling off. 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. At the minimum speed, the Normal Force between the wheels and rail goes to zero (the wheels just "kiss" the track), so the centripetal force is just equal to the weight, w = mg. An aside: 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.

Wednesday 2/28: UCM Revisited. Centripetal Force. 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. For Exam 2: NO Newton's Law of Universal Gravity, NO artificial gravity in rotating space stations. Review for Exam 2. Return some quizzes. Q13 will be after Spring Break.

Thursday 3/1: Exam 2.

Friday 3/2: Spirit Day. No classes. Effective start to Spring Break.

### Week of March 5-9, 2007.

SPRING BREAK -- NO CLASSES.

### Week of March 12-16, 2007.

Monday 3/12: 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.) Revisit the Space Shuttle in orbit problem. Find g at r=6,770,000 meters in class. Going backwards through the problem and find v (the speed of the Shuttle in orbit) and T (the period or time to make one orbit). Originally has estimated T = 90 minutes = 5400 seconds. Actually, using correct g for Low Earth Orbit, we get T = 5542 seconds, or off by two minutes and 22 seconds. For circular orbits, each r has its own g, v and T -- higher orbits see weaker gravity, travel slower and take more time.

Tuesday 3/13: 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. Why Boats Float. Example: Front lab table as a 250 kg boat with 4.00 m³ volume. Q13 Take-Home due Thursday 15 March 2007.

Wednesday 3/14: 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. 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. Absolute (total) Pressure vs. Gauge Pressure (difference between two readings).

Thursday 3/15: X2 returned. 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. Q14 is a Take-Home due Tuesday 20 March 2007.

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

Friday 3/16: PHYS-1070 Does NOT Meet This Friday.

### Week of March 19-23, 2007.

Monday 3/19: Smooth Fluid Flow. Bernoulli's Equation and the Continuity Equation. Water Tower and the Faucet Problem. Why the water tower needs a vent. 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.) NOTE: Q14 will now be due on Wednesday 21 March 2007.

Tuesday 3/20: Bernoulli continued. 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. Mackinac Bridge. 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.

Wednesday 3/21: 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: No Dr. Phil office hours after about 11am.

Thursday 3/22: 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. I-57 in Chicago and the expanding asphault. Question: Does the material expand into a hole when heated, or does the hole expand? Volume Expansion of Solids and Liquids. First set of Sample Exam 3's handed out. (Click here and here for a copy.) Handout on some of upcoming lectures. (Click here for a copy.) Q15 Take-Home due Tuesday 27 March 2007.

NOTE on Q15: We haven't covered all the material for Q15 yet, but on Monday we'll talk about the Ideal Gas Law (PV/T = constant) and "our" version of the Ideal Gas Law for Physics: P1V1/T1 = P2V2/T2, where one has to use Absolute temperatures, because T1 and T2 cannot be either zero or negative. If you understand what I just wrote, you can probably finish Q15 before Monday.

Friday 3/23: PHYS-1070 Does NOT Meet This Friday. (NOTE: We DO Meet next Friday 30 March 2007 for a normal class, with Exam 3 the following Thursday 5 April 2007.)

### Week of March 26-30, 2007.

Monday 3/26: Volume Expansion of Solids and Liquids. Ideal Gas Law (PV/T = constant). Heat Energy (Q) and Temperature Change & Phase Change. Add/remove Heat Energy Q will raise/lower the temperature of a material using the Specific Heat (J/kg·°C) for objects of mass m, or the Heat Capacity (J/mole·K) for objects with n moles of atoms or molecules. Add/remove Heat Energy Q will change its phase between solid-liquid-gas using the Latent Heat of Fusion, Lf, between solids and liquids, or the Latent Heat of Vaporization Lv, between liquids and gasses. Example: Take a 1.00 kg block of ice from the freezer (T = -20°C, about 0°F) and heat it in a pan until it is all boiled away. (1) Heat ice from -20°C to ice at 0°C; (2) melt ice to water at 0°C; (3) heat water from 0°C to 100°C, (4) boil water into steam at 100°C. Using Power = Work/time, we can apply heat at the rate of 1000 W = 1000 J/sec.

Tuesday 3/27: Ice has a low specific heat, so ice very quickly warms up to the melting point. Wet ice is at T = 32°F = 0°C = 273K. The specific heat of water is 4186 J/kg·°C-1 = 1 Calorie (1 "Big C" Calorie = 1 Food Calorie). This is the energy it takes to raise the temperature of 1 kg of water by 1°C. (In the English system, we have the British Thermal Unit, where 1 BTU is the energy it takes to raise the temperature of 1 pound of water by 1°F. You see BTU ratings on air conditioners and furnaces, for example.) "A watched pot never boils". Water will boil in a pan for a long time. Indeed, the latent heat of vaporization of water, 2,260,000 J/kg is huge and important for cooking and putting out many fires. Water doesn't drown the fire, it removes heat from the fire, lowering its temperature eventually below the ignition point. Can't use water on all fires. Class D (magnesium) fires, electrical fires. Halon gas fire supression systems protect computer hardware in a big data center, but displace the breathable air -- get out when alarm sounds! 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.

Wednesday 3/28: 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. NOTE: Not enough time to give Q16 in-class today -- will give Q16 on Thursday. Q17 Take-Home, due Friday 30 March 2007.

Thursday 3/29: 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). Q16 in-class.

Friday 3/30: This Friday will be a normal class, with Exam 3 on Thursday 5 April 2007. 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. Second Set of Sample Exam 3's handed out. (Click here and here and here for a copy.)

### Week of April 2-6, 2007.

Monday 4/2: Tuning forks, resonance boxes. The speed of sound in air: 334 m/s @ 0°C and 344 m/s @ 20°C. Takes time for sound to travel. Constructive and Destructive Interference. Acoustics of concert halls. "Normal" human hearing is frequencies from 20 Hz to 20,000 Hz.

Tuesday 4/3: The range of "normal" human hearing: 20Hz-20,000Hz (10 octaves). Artilleryman's ear -- mid-range hearing loss. dB = decibel, a logarhythmic scale. The speed of sound in air. Sonic Booms and other shockwaves. Bullwhip stories. The first silencers were for rifles, so you could hunt in town without disturbing people. Story of tiny sonic booms from bullets reflected by telephone poles... early 1900s.

Wednesday 4/4: Waves take time to travel. Sound takes time to travel. An echo takes times to get to the reflecting surface and travel back -- to and fro. A Doppler Shift occurs when a sound wave is generated at one place and you are moving relative to it. Warning horn on a moving train, for example, or the siren on an ambulance. When the sound source is coming towards you, the frequency is higher. When the sound source is going away from you, the frequency is lower. Simple radar and sonar measure distances by timing the wave and its reflection. The time between two pulses gives you the speed of the target object. Doppler radar (and sonar) measure the speed by measuring the frequency shift of the reflection -- if the target is not moving, then there is no frequency shift. Demo: Doppler Rocket on a string swung over Dr. Phil's head. You can hear the change in the frequency as the Doppler Rocket moves towards you or away from you. Q18 in-class. Return a stack of old quizzes.

DUE TO ICY ROADS AND TREACHEROUS DRIVING, Exam 3 has been rescheduled to TUESDAY 10 April 2007.

Thursday 4/5: Exam 3 rescheduled to Tuesday 10 April 2007. 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. Topic 2 Worksheets (Click here for 1st Worksheet and Directions).

Friday 4/6: PHYS-1070 Does NOT Meet This Friday.

### Week of April 9-13, 2007.

Monday 4/9: A Nickel coin has a mass of 5 grams, so about 1/10th of a mole. Find number of free conduction electrons, and number of Coulombs of positive and negative charges. 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. "Action at a distance" -- Gravitational, Electric and Magnetic Forces are not Contact Forces - Require Fields. 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).

Tuesday 4/10: Exam 3, rescheduled from last Thursday 5 April 2007 due to icy conditions on roads. Q19 Take-Home, due Thursday 12 April 2007.

NOTE: Dr. Phil often wonders why, after everyone shows up for an Exam one day, hardly anyone shows up for class the next day? This is a problem because we have only a few class days left, yet we are covering a wide range of new material.

Wednesday 4/11: 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. 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. Topic 2 Worksheets (Click here for remaining Worksheets and Directions)

Thursday 4/12: D.C. and A.C. circuits. Current defined. 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"). Series and Parallel Resistors. Two devices connected together in a circuit can only be connected two ways: series or parallel. In Series, same current, share voltage. Equivalent resistance is always larger. In Parallel, same voltage, share current. Equivalent resistance is always smaller. Resistor Network Reduction. The battery only "sees" an equivalent resistor, which controls its current. So we could (but won't) reduce a resistor network to a single equivalent resistance, go back and fill in the table for V = I R and then P = I V. In the example sketched in class, Resistor 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. First day to accept finished Topic 1 Book Reports. (Last day to accept without penalty is Monday 16 April 2007 by 5pm.) First set of Sample Final Exam's handed out. (Click here and here for a copy.) Q20 Take-Home, due Tuesday 17 April 2007.

Friday 4/13: PHYS-1070 Does NOT Meet This Friday. (NOTE: We DO Meet next Friday 20 April 2007 for our FINAL class session, with the FINAL EXAM on Tuesday 17 April 2007.)

### Week of April 16-20, 2007.

Monday 4/16: "Magnetism is just like Electricity, only different." Real Magnets are dipoles (North and South ends, linked). Break a magnet in half, and you either get two new magnets -- or nothing. So far, there is no evidence that there are Magnetic Monopoles (magnetic charges: isolated North or South poles). Rules similar to Electric Charges: Unlike poles attract, like poles repel. Demos: Cow magnets -- powerful cylindrical, rounded end magnets which get dropped into a cow's first stomach, to collect nails, bits of barbed wire, etc. from continuing on to the cow's other stomachs. Broken cow magnets show a radial crystalline structure due to the alignment of small magnetic domains -- what makes the magnetic field strong also makes the magnet physically weak is some directions, hence the breakage across the radially aligned grains. Dropping a permanent magnet can result in a reduction of its magnetic field as the shock allows some iron atoms to flip 180° and therefore cancel instead of add to an adjacent iron atom's magnetic field. The horizontal compass needle rotates until its North end points North (or rather to the North Magnetic Pole, which is of course a South pole of the Earth's magnetic core); the vertical compass rotates so that it lines up with the B-field along the surface of the Earth at the point. At the Equator, the vertical magnetic should be parallel to the ground, at the magnetic poles, it should be perpendicular to the ground. Is the Earth's magnetic field going to flip some day? And what about Mars? SI Units for B-field: (1 Tesla = 1 T). "Other" unit for B-field: ( 1 Gauss = 1 G ; 1 T = 10,000 G ). Earth's B-field is about 1 Gauss at the Earth's surface. Example of the 4T NMR magnet at Michigan Tech and the 10-foot radius line on the floor and erasing ATM cards within that circle

Tuesday 4/17: 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. In vacuum, 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). Microwave ovens have metal screens in their windows -- the centimeter-range sized EM waves cannot see the "small" holes in the screen, so they bounce off the window as if it were just like the metal in the other five walls. Discussion of how microwave ovens "cook" food. Second set of Sample Final Exams handed out. (Click here for a copy.) Q21-22 Double Take-Home, due Thursday 19 April 2007.

Wednesday 4/18: 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. Corner and Corner Cube reflectors. 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.