Dr. Phil's Home

Lectures in PHYS-1070 (18)

Updated: 03 July 2006 Monday.

Week of June 26-30, 2006.

Monday 6/26: LAST CLASS. A brief look at Atomic and Nuclear Physics. Handouts: Dr. Phil's Periodic Table. Quiz 21+22 Take-Home, due at Final Exam (or by Friday 30 June 2006 at NOON). NOTE: There is a glitch in the PDF file for Quiz 21 -- but it doesn't affect the formula you need to use, so ignore it. --Dr. Phil

Tuesday 6/27: FINAL EXAM. TWO HOURS: 2:00 to 4:00pm, 1110 Rood Hall.

Wednesday 6/28: Office Hours - Noon to 3pm.

Thursday 6/29: Not on campus today.

Friday 6/30: Office Hours - Noon to 3pm.

Monday 7/3: Grades due by NOON to Registrar. Do NOT call me in the morning.

Week of May 8-12, 2006.

Monday 5/8: 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 5/9: "Speed Limit 70" First Equation: Speed = Distance / Time. Development of Speed equation for Constant or Average Speed. Topic 1 assigned. (Searchable booklist available online here --or-- the entire handout in .pdf format here.)

Wednesday 5/10: No class.

Thursday 5/11: 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. 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. Q1 and your PID number. (If you missed class on this day, check with Dr. Phil sometime soon.)

Friday 5/12: Dr. Phil's Reasonable Significant Figures. 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. Q2 in-class quiz. Q3 Take-Home handed out.

Week of May 15-18, 2006.

Monday 5/15: NEWS: Saturday new World Record in 100m dash -- 9.76 seconds. Speed. 60 m.p.h. = "A Mile A Minute". (1848: The Antelope) The P-O-R (Press-On-Regardless) road rally problem. "You can't average averages." The consequences of Falling Down... ...and Falling Up. The Turning Point ( v=0 but a = -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. Adding and subtracting vectors: Analytical method.

Tuesday 5/16: 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. Finding the final vector velocity of The guy with the fedora and the cigar problem. Q3 due by 5pm. Q4 take-home handed out, due Thursday 18 May 2006 by 5pm.

Wednesday 5/17: No class.

Thursday 5/18: 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. Space Shuttle in Low-Earth Orbit. (There's still gravity up there!)

Friday 5/19: Exam 1 Q5 take-home handed out, due Tuesday 23 May 2006 by 5 pm.

Week of May 22-26, 2006.

Monday 5/22: Classic Simple Pursuit (Cop and the Speeder). 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.) SI unit of force: Newton (N).

Tuesday 5/23: Force is a vector. Free Body Diagrams. Normal Force (Normal = Perpendicular to plane of contact). Sum of forces in x or y equations. Example of 125 kg crate being dragged/pushed around. Variations as we allow for an applied force that it at an angle. 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.). "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. 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. 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. Hand out first sample exam pages for Exam 2. Q6 in class. Q7 Take-Home, due Thursday 25 May 2006.

Wednesday 5/24: No class.

Thursday 5/25: Atwood's Machine -- two masses connected by a single cable via a simple pulley. 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 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"). Anti-Lock Brakes and Traction Control.

Friday 5/26: Linear Momentum ( p = mv ) is a vector quantity. Newton's form of the 2nd Law. 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. 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. 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.Q8 in-class. Q9 Take-Home, due Tuesday 30 May 2006.

Week of May 29 - June 2, 2006.

Monday 5/29: MEMORIAL DAY. No classes.

Tuesday 5/30: 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). 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. Elastic collisions -- conserve both momentum and K.E. Why you want inelastics collisions in a wreck. "Adobe: The Little Car Made of Clay". 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. 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. Hand back Exam 1. Extend deadline on Quiz 9 Take-Home to Thursday. Quiz 10 Take-Home, due Thursday 1 June 2006.

Wednesday 5/31: No class.

Thursday 6/1: 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. 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. UCM Revisited. Centripetal Force. No such thing as Centrifugal Force. Only the Centrepital Force, which points radial inward, just like the centripetal acceleration. The story of the 50,000 rpm Ultra-Centrifuge and the Fresh Rat's Liver. Making "artificial gravity" for long-duration space flight by living in a rotating object. Continue to extend Take-Home quiz deadlines, for those who need more time.

Friday 6/2: NOTE: Exam 2 has been moved to Monday 5 June 2006. DVD clip: 2001: A Space Odyssey (What would it look like to have use centripetal force for artificial gravity? Stanley Kubrick's 1968 movie showed us a large rotating space station and a smaller rotating carousel on a ship to Jupiter.) Continue with Conservation of T.M.E. (P.E. + K.E.) on a roller coaster. Total energy limits maximum height. 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. 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. Review for Exam 2. Quiz 11 take-home, due Tuesday 6 June 2006.

Week of June 5-9, 2006.

Monday 6/5: Exam 2 today!

Tuesday 6/6: 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. 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. Quiz 12 Take-Home, due Thursday 8 June 2006.

Wednesday 6/7: No class.

Thursday 6/8: Mass-to-Volume Ratio (Density). NOTE: Do not confuse the Density of the Materials with the Mass-to-Volume Ratio of the OBJECT. 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. First Sample Exam 3. Quiz 13 Take-Home, due Friday 9 June 2006.

Friday 6/9: Bernoulli continued. 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. 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.

Week of June 12-16, 2006.

Monday 6/12: 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. 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. Second set of three Sample Exam 3's. Q15 Take-Home, due Thursday 15 June 2006.

Tuesday 6/13: 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. Heat Energy (Q) and Temperature Change & Phase Change. Water has a high Latent Heat of Vaporization: (1) Long boiling time, (2) Firemen use it to take heat energy out of the fire zone. 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). No volunteers for assisting with last demonstration -- so just ended class.

Wendesday 6/14: No class.

Thursday 6/15: 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. The range of "normal" human hearing: 20Hz-20,000Hz (10 octaves). Tuning forks, resonance tubes. Beat frequency. Constructive and Destructive Interference. Artilleryman's ear -- mid-range hearing loss. dB = decibel, a logarhythmic scale. Some review for X3. Return X2. Q16 in-class.

Friday 6/16: Exam 3

Week of June 19-23, 2006.

Monday 6/19: 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. The Realization that Electricity and Magnetism were part of the same Electromagnetic Force was a great triumph of 19th century physics. Franklin's One-Fluid Model of Electricity. 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.

Tuesday 6/20: Gravitational, Electric and Magnetic Forces are not Contact Forces - Require Fields. 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. D.C. and A.C. circuits. Ohm's Law. 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. Q17 in-class. Q18 take-home, due Thursday 22 June 2006.

Wednesday 6/21: No class, but special office hours: Noon to 3pm.

Thursday 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.) Real batteries consist of a "perfect" battery (Electromotive force = emf) in series with a small internal resistance, r. As chemical reaction in battery runs down, the internal resistance increases. Tip for weak car battery on cold day: Run headlights for 30 to 90 seconds. High internal resistance will warm the battery and make it more efficient. Proper procedure for jump starting a car. (And why doing it wrong ranges from dangerous to deadly.) DC can use batteries or generators. Lower voltage by using a resistor. Raise voltage by putting more batteries in series. AC from generators. Raise and lower voltage by using a transformer. Why AC for power lines? By raising voltage on long-distance power lines, lowers current and substantially improves the effiiciency due to reduced energy losses. Superconductors.

Friday 6/23: The Electromagnetic Wave travels at the speed of light. c = 300,000,000 m/s = 186,000 miles/sec. Visible Light: ROYGBIV. Electromagnetic Spectrum (ELF, Radio, Microwaves, IR, ROYGBIV, UV, X-rays, gamma rays). 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. 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".) The Law of Refraction - Snell's Law. Light bent at the interface between two media, because the speed of light changes in the media. If going from an high index of refraction media to a lower index media, have a chance for Total Internal Reflection (T.I.R.). Return X3.All-Titanic Sample Final Exam. Q19-20, double take-home quiz, due Monday 26 June 2006.