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Course: Physics 101, Conceptual Physics Fall 2004

This course attempts to give a broad introduction to the "rules of the game" of the physical universe; that is, to the exciting world of physics. While the course is basically non-mathematical, some knowledge of high-school algebra is pre-requisite, and algebra (such as solving simple equations, or using powers of numbers) will be used regularly. To understand physics, one MUST be able to express central concepts both in words and equations. Little calculational ability is expected, however.

Homework and Webassign: Each daily homework assignment consists of two parts, the set of Practicing Physics pages for the chapter and the chapter assignment from Webassign. The Practicing Physics pages for a given set of chapters will be due at the time of the quiz for those chapters. The schedule of dates for the Webassign assignments will be shown at the Webassign site.

Webassign: Due to budgetary cutbacks we are using a web-based homework system for this course. It is less than ideal, but does provide good coverage of the material. After you obtain your Webaccess student account, you will find that the Webaccess page is that which you will want to log into in order to do your homework assignment. However, I will continue to use the course syllabus at the class course page to indicate the schedule of lecture reading and quizzes. There are two parts to most of the Webassign sets. The questions from Part A receive fractional credit compared to Part B, and are answered generally by a text answer. Part B involve a calculated answer.

Extra credit: I will assign a number of problems on Webassign. Each problem specifies how many points that will be credited. Regular credit for a given assignment will be 20 points, including 5 points for completed Practicing Physics pages. However, there will be more than 15 points worth of problems assigned. Any extra points earned on an assignment will be credited towards your extra credit pool, to be used to bring up assignments to the maximum of 20 points per assignment where you may have received less than full credit. Unlike quiz and final scores, homework grades will NOT be strictly curved, as I expect that the median score on the homework to be considerably higher than if no extra credit were added..

Chapter Link:

Click on to jump to specific chapter: Ch 1, Ch 2, Ch 3, Ch 4, Ch 5, Ch 6, Ch 7, Ch 8, Ch 9, Ch 10, Ch 11, Ch 12, Ch 13, Ch 14, Ch 15, Ch 16, Ch 17, Ch 18, Ch 19, Ch 20, Ch 21, Ch 22, Ch 23, Ch 24, Ch 25, Ch 26, Ch 27, Ch 28, Ch 29, Ch 30, Ch 31, Ch 32, Ch 33, Ch 34

 

Syllabus

The syllabus closely follows the table of contents of Hewitt at least as of now - we cover one to two chapters of Hewitt a day. It is expected that most days you will read the chapter, do the Practicing Physics pages and the assignment at Webassign. At the end of each class there will be a brief in-class quiz, usually closely tied closely to what you did for homework. At the mid-point (Ch 1-5) and end of Part 1 (Ch 1-10), Part 3 (Ch 11-18), Part 4 (Ch 19 - 26) and Part 5 (Ch 27 - 34) there will be major multiple choice quizzes.

August 26-31: Introduction (s), About Science

For next time - Read Chapters 1 & 2, do the Practicing Physics pages for the two Chapters and the homework at WebAssign.net. [There are two HW parts to each day, the practicing Physics pages for the chapter and the WebAssign pages]

(The quiz on Tuesday will only cover the Practicing Physics pages - normally it would cover both parts of the HW)

Introductions

names of neighbors, check with your neighbor

Physics - the basic science

Tries to explain (develop theories ) for physical phenomena of universe in mathematical terms that can then be tested experimentally, expresses results mathematically.

Math - requirement - algebra (equations) so I can write equation, use things like area of circle, circumference of circle, etc., Many physical phenomena most clearly understood by mathematical relationship. Use proportions - example of triangles to illustrate, then extension of triangles to size of earth, discuss Eratosthenes 235 BC 800 km Alexandria to Syene. shadow 1/8, so similar triangles, distance 1/8 radius, 8 X 800 = 6400 km radius.

Some definitions

Law

- an idea to be tested. After a group of related hypotheses have been verified, they can form a theory.

Theory

Aug 31- Chapter 2 - Newton's First Law -Inertia

For next time - read Ch 3, do the Practicing Physics pages and the HW assignment at WebAssign.

Aristotelian physics; Copernicus,

Fixed universe, source of motion in object, geocentric vs heliocentric

Gailileo's inclined planes

Objects are lazy "Motion continues"

Newtons First Law: inertia

Net Force à motion

Equilibrium, support force, the moving earth.

Sept 2: Chapter 3 - Linear Motion

For next time - read Ch 4, do the Practicing Physics pages and the HW assignment at WebAssign

Highlights

Motion is relative

Speed

Speed = Distance/time (think miles/hour, or miles per hour)


Instantaneous vs. average

Or: speed = (total distance covered)/(time interval)
or v= d/t
speed equals the rate of change of distance
(that is, change in distance, per second)

Velocity

In physics, velocity is defined precisely as giving the speed and the direction. It what we call a vector. Again, have average and instantaneous. But a velocity may be changing even though the speed is held constant. (How?)

Acceleration: rate of change of speed (speeding up or slowing down, how fast)

E.g., miles per hour per second - how many miles per hour the speed changes per second

Velocity change = acceleration X time

in "algebra-speak", Dv = at

Or: acceleration = (change of velocity)/(time interval) (a = Dv/Dt - we often use the symbol D to stand for "change of", so it reads "acceleraion equals change of velocity divided by the change of time.")

How far?

Distance = avg speed X time

= (1/2 X acceleration X time) X time

or d = 1/2 at2 (= 1/2 a x t x t )

Free Fall, Acceleration caused by gravity at sea level: g =  10 m/s2

Discuss question of forces on objects falling at same speed

 

Sept 7: Chapter 4 - Newton’s Second Law

For next time - read Ch 5, do the Practicing Physics pages and the HW assignment at WebAssign

Highlights

Second law: force, mass and acceleration (F=ma or a = F/m)

Units: newtons= kgm m/s2

Force: applied force accelerates an object – push or pull.
Acceleration resisted by inertia (mass)

Net force – resultant of all applied forces (add vectors)
Sum of forces = zero: equilibrium (no acceleration, but can be moving –dynamic - or at rest - static)

Tension

Force yields acceleration

Free Fall – acceleration = g

g= F/m » 10 m/s2 ; Gravity - g = F/m, force of gravity on mass = weight

Mass and Weight

Kilograms and newtons (weight of 1 kilogram = 2.2 pounds)
W = mg

Friction

Proportional to weight, friction coefficient

Static and kinetic

Opposes motion
Depends on weight, not area
Static larger than dynamic
(fluids, including air) – air resistance. Terminal speed

Free Fall and non-freefall – air resistance

Mass resists Acceleration

Vectors

Length and direction

Addition

Head to tail, parallelogram methods

Examples

Sept 9: Chapter 5 – Newton’s Third Law

For next time - read Ch 6, do the Practicing Physics pages and the HW assignment at WebAssign. Next time there will be multiple choice quiz on Chapters 1-5, Bring a Zeus form!!

Highlights

Forces and Interactions

Third law: action and reaction (equal and opposite forces)

Defining the system

Support forces (constraint forces, reaction forces, normal force)

Examples: Block on table, donkey and cart, rocket, road, ball and bat, ball and wall, two skaters pushing off, rifle and bullet, earth and moon

vectors

adding

head to tail method, parallelogram method of adding two vectors

Examples

Components

Using right triangles

***: Last day to add

Sept 14: Chapter 6 - Momentum (Quiz Ch 1-5, bring Zeus form)

For next time - read Ch 7, do the Practicing Physics pages and the HW assignment at WebAssign

Highlights, Ch 6

Momentum

(= mass times velocity=mv)

impulse

= Force times time =change of momentum

=F Dt = m (Dv/Dt) Dt= m Dv = D(m v)

Says, apply a force for a time, causes change in momentum)

Examples:

Increasing momentum: bat, bow and arrow, golf drive, loose coupling of train cars.

Decreasing momentum gradually: catching hardball, diving into water (not concrete), falling on a mat.

Momentum transferred? – ball against wall: more if bounces or sticks?

"Conservation of momentum"

Isolated system (!) then momentum is constant (Smvinitial = Smvfinal)

Eg. Kinetic balls

Sept 16: Chapter 7 - Energy

Assignment:

Read Ch8, paying attention to the review questions (!) , esp 4,9,15,26,35

Do Practicing Physics :31à 36 and the webassign questions on ch 8

Highlights

Energy

Work, power, energy, kinds of energy, conservation of energy

Work = force ´ distance (cf. Impulse) = newton meters = joules

Power = work/time; the rate of doing work (cf. velocity) = joules/sec = watts!

So 1 kWh (what you are charged for by PGE) = 3.6 million joules. In terms of work, the joule is small. (if you are a cross-word fan, you’ll also see ergs they are even smaller = 1/10 millionth of a joule. A food calorie is 4.2 kJ (k = 1000 = 103) Also Hewitt notes that gasoline has 40 MJ/liter (M = Mega = 106)

Then: energy = ability to do work

Comes in many forms.

LAW OF CONSERVATION OF ENERGY (a big one!!)

Conservation of Energy in popular sense vs. in physics sense?

At what point in its motion is the KE of a pendulum bob the greatest? The least? Half its maximum? What is the PE at each of these points?

Questions

Conservation – Kinetic and Potential –
1. speed at bottom of incline vs. dropped from edge?
2. Efficiency – the most work one can get?
3. Work done lifting vs. holding up – work done by a statue? (difference of biological vs. physical work)

Some class questions

Can something have energy without momentum? How about kinetic energy? How about momentum without energy?

Why is there no work done when the force is perpendicular to the velocity of the object?

If a golf ball and Ping-Pong ball move at the same kinetic energy, which has the greater speed? Similarly, in a gaseous mixture of heavy (say O2) and light (say H2) molecules, which "diffuses" faster?

Does a car use more gas when its lights are turned on? Does the overall consumption of gas depend on whether the engine is turned on when you are using the lights?

A pair of identical lumps of clay collide and come to rest as a result. Is momentum conserved? Is kinetic energy conserved? Is total energy conserved?

Consider the swinging balls demo we saw. Why is that that if we release two balls, two balls pop out, and not one ball at 2X the speed?

Sept 21: Chapter 8 – Rotational Motion

Assignment:

Read Ch 9 (to pg 166) and Ch 10 (to pg 188 only);

Do Practicing Physics pp 37-45 and Chapter 8 HW at Webassign

Highlights

rotational inertia (~ m r^2),

e.g. balance pole, using arms, etc

rotational velocity

(how fast it rotates or goes around) (~v/r )

angular momentum

(=mvr, ~ rotational inertia ´ rotational velocity)

torque that which causes rotation acceleration

(=r F, ~ lever arm ´ force), (units: foot-lbs or newton-meters)

conservation of angular momentum

(no torques) (mvr)Initial= (mvr)Final, BUT since an isolated body can change its rotational inertia (relative to its center of inertia), it can change its rotational velocity – e.g., cats, divers, skaters, etc. (demo on turntable)

center of mass

(essentially same as center of gravity), about which free body rotates, can think of all mass centered there, extended body acts like point mass.

Example, girl on plank – 40 kg, 100 kg, 10 m

Stability:

Vertical from center of gravity over base, so no torque tending to rotate-

centripetal (NOT centrifugal) force

result from inertia – bodies want to go in straight line, must be forced to turn – think of string and rock.

 

 

Sept 23: Chapter 9 - Gravity AND Chapter 10 Projectile and Satellite Motion;
Review of Mechanics End part 1
(Quiz on part 1 next time: bring ZEUS form)

Assignment: Read Chapters 11 and 12 and do the practicing physics pages and at least 15 points of problems at WebAssign.

Note: due to the quiz on part 1, there won't be a daily quiz on the reading, BUT questions on them will be incorporated into following quizzes.

Gravity

Gravitation, Newton’s Law of - Comments on importance - Impact on culture - Fundamental force, shapes universe

F=Gm1m2/r2, ~masses of each, ~ 1/r2

G = 6.7 x 10-11 N m2 /kg

Relationship to weight (F=mg), weightlessness.

Other fundamental forces, electromagnetic, nuclear strong, nuclear weak.

Inverse Square Law:

Discussion of 1/r2 physical quantities: gravitational force, electric force, light intensity, sound intensity, anything propagated from a point source (paint spray spreading).

tides, effect of moon vs. sun, gravitational field.

Full, new ->"spring tides", 90 deg "neap tides"

Gravity inside a planet, or a shell.

Satellites

Drop of earth ~ 5 m in 8 km

Free fall d = 5 m after 1 sec: if v ~ 8 km/s, orbit! (Newton’s cannon)

If more -> elliptical

Potential and kinetic energy in orbit,

Does rotation of earth affect?

Launch (ve ~0.5 km/s @ equator)

Apparent orbit

Escape velocity , black holes

ve escape velocity = speed at which object leaves orbit, about 11.2 km/s for earth at surface

ve2 ~M/d (d=distance to center)

For sun (radius ~ re x 100, (re = 6.4 million m or 6 thousand km) ; Ms ~Me x 3 x 106), , ve,S =620 km/s

Speed of light : c= 3 x 108 m/s. Nothing travels faster. IF sun shrank so ve > c, NOTHING escapes, including light! black hole. True if sun shrank to 1/106 (one millionth) or about rS~3 km

earth drops 5 m in 8000 m. (or use 1 m in 1600 m, or about 1 m/mile)

Expansion of universe: a question right now, but regardless, gravity the most important force in nature on the large scale.

Projectile Motion

The essence: horizontal motion is constant, vertical motion changes as a freely falling body. Dhorizontal = vhorizontal t; Dvertical = vvertical t - 1/2 g t2

Review, Part 1:

Inertia, force, speed, velocity, acceleration, mass vs weight, friction, vectors vs scalars, energy, potential and kinetic, power . . .

Examples:

inertia - mass; "lazy", accelerating, going around a corner,

force - and reaction; force due to body = weight =mg

speed - mph, dist/time velocity: net distance

acceleration - rate of change of velocity,

force - always mass times acceleration:  newtons; friction force, always opposes motion, ~ mg

vectors - direction and magnitude,

energy: mechanical kinetic and potential: many other forms. joules, calories (vsvs. kilocalories), kWh.

Power: rate of using or changing energy: watts

Tides - non-uniform pull of moon (sun's pull much stronger)

Selected questions

momentum, angular momentum, the conservation laws (3),

units: kg, m, s, N, joules, watts,

weight mg, momentum mv, kinetic energy 1/2 mv2, gravitational potential energy mgh rotational inertia ~mr2

angular moment ~ rotational inertia X angular rate of rotation ~ mvr

centripetal acceleration: mass on string -> tension (rock seems to pull "outward" but goes in straight line when released - inertia!)

gravity (tides)

Conservation Laws:

Conservation of momentum - no outside forces in direction of motion

Conservation of angular momentum - no outside twists - earth absorbs, etc. (bicycle,

Conservation of Energy (but must define the system carefully - e.g., refrigerator)

Sept 28: Chapter 11 - The Atomic Nature of Matter; AND Chapter 12 Solids (part 1 quiz at end)

Read chapters 13 AND 14 for next time, do the Practicing physics pages for both, as always.

The Atomic Nature of Matter

Greeks – speculation of a smallest (Democratis)

18th –19th century chemistry – combination of elements ->individual atoms, weights (Avogadro, Loschmidt)

Modern understanding – atom – 10^-10 m, joined together, makeup molecules. Molecules vary from 2 atoms to millions of atoms (e.g. protein molecules)

Atoms made of nucleus, electrons, all mass in nucleus.

nucleus – 10^-15m, protons and neutrons

surrounded by thin cloud of electrons (size depends on wave properties)

electrons in shells, electrons neg., protons positive, neutron (like protons) neutral.

Atomic number, atomic mass, Avogadro’s number. Shells, charges outside closed shells determine chemical properties.

Nucleus – protons and neutrons, now know p and n made up of smaller particles "quarks" -

Anti-matter

Mass of atom ~ 1/6 x 10^-23 grams (H)

Periodic Table – shows shells – similar elements having similar outer shell.

Phases – solid liquid gas plasma

Solids

– molecule in regular, fixed arrays, bound together. Binding may be "ionic, covalent, metallic, "van der Walls"; size varies from 2 atoms to millions.

Properties of solids: molecules connected by springs, vibrate as heat up, expand.

Tension, compression, strength of arches

Scaling

Strength ~area - r^2

Weight ~ volume - r^3

Wind resistance ~ area

Sept 30: Chapter 13 - Liquids; Chapter 14 - Liquids; Gases and Plasmas: End part 2

Chapter 15 for next time and start of Chapter 16 (about to page 313)

Liquids

Density
Pressure in a liquid (liquid pressure = weight density X depth)
Bouyancy (weight of displaced liquid): Archimedes' Principle
Pascal's Principle: (pressure transmitted throughout)
Surface tension, capillarity

Gases

Atmosphere, atmospheric pressure, mass of air (1 m^3 ~ 1 1/4 kilograms at sea level)
Air Pressure ~1/2 @ 5.6 km,

Weight of air ~ 10 N/cm^2 or 10^5 N/m^2 ~ 100kPa , ~ 10.3 m of water

Barometers

Gas Law: pressure-volume (Boyle's law - const T)

PV = nRT which says PV= cons't for fixed temp, V~T for fixed P (eg., atmospheric)

Gases cool on expansion -

Bernoulli's Principle:

Air Speed increases, pressure decreases.

Plasma - think neon display

Review Chapters 12-14

In essence, these chapters teach us that all matter is composed of atoms held together by electrical forces. All materials exist as solids, liquids or gases given the right conditions. Solids are held most tightly; as heat is applied, the solid melts and becomes liquid, and as heat is applied further, it becomes gas. All materials can be characterized by their density (greatest for solids, least for gases) Solids can be in compression or tension. Liquids and gases can only undergo compression, and do not support tension. A important concept for both liquids and gases is pressure (force/area) and buoyancy (uplifting force equal to weight of displaced fluid.) Pressure is the same at the same height in either a liquid or a gas. Additional pressure applied is transmitted uniformly through the fluid. In Ch 15 we find both solids and liquids expand some with increase in temperature, but resist compression. However, gases change their volume greatly with changes in temperature or pressure (V ~ T/P, where T measured in kelvins). Bernoulli's principle says that a gas has reduced pressure where it moves faster.

 

October 5: Chapter 15 Temperature, Heat, and Expansion; Start Chapter 16 - Heat Transfer

Temperature,

scales: relative measure of internal kinetic energy, direction of heat flow, measure - degrees. Temperature Calibration - "fixed points", absolute zero.

Heat - another form of energy!

quantity - usually calories, Btu's, Calories. Internal amount - heat capacity - touching a hot iron, hot wood, hot Al foil, etc. Water - high heat capacity (water: 1 cal/gm-BIG) e.g. Pie Vs filling

Expansion

of solids (demo), ocean levels (more on thermal expansion than change in amount of mass)

Water expands when freezes

Heat Transfer

3 primary means: Conduction, Convection, Radiation

Conduction: direct contact exchange of heat, usual method between solids

Convection: motion of molecules carrying kinetic energy, exchanging energy

Radiation: heating by photons, that is, by electromagneitc radiation; e.g., the sun.

? Why do you feel cooler when you move away from a fire, but always the same with the sun?

Example of thermos bottle - controls all three.

October 7: Finish Chapter 16- Heat Transfer; Chapter 17 - Change of Phase:

Ch 18 is for next time and that finishes part 3. There will be a Multiple Choice quiz on parts 2 & 3 in a week from today.

Change of phase:

Evaporation (condensation); melting (freezing); absorb heat (lose heat)

Associated with change in connection of molecules to neighbors; more kinetic energy makes it more difficult for molecules to "stick".

Evaporation - those molecules leaving take energy, work of "leaving", leaving less - cooling

Occurs all the time. Higher temp - air holds more water vapor, less likely to condense.

Clouds condensation

Boiling - change of phase interior of liquid. Occurs at a definite temp for given conditions (temperature, atmospheric pressure) = BP

Vapor bubbles ~ 1 atm internal, increase or decrease by pressure change. Covering a pan reduces heat needed - mostly due to reduction in loss of heat.

Cooling, refrigeration uses, air conditioning, "heat pump"

Melting, "regelation"

Kinetic energy added enough to disrupt rigid bonds.

Skating e.g.

Latent heats

Evaporation, Condensation, melting, freezing, latent heat

Evaporation (i.e., boiling) is a cooling process!! (takes away heat)

Latent heat - amount of energy to change phase, temperature remains fixed while at phase change. Water- 80 cal/gm melting; 540 cal/gm boiling

 

October 12: Chapter 18- Thermodynamics; End part 3

(Multiple Choice Quiz on parts 2 and 3 next time)

First Law

Sum of all energy changes = 0

Adiabatic process

Change of energy = heat in – work out

No heat gained or lost - important for engines, atmosphere - work done = loss of internal energy, cooling; work on = increase of internal energy (bicycle pump)

E.g. Cooling at higher elevations, (~ 10  C per km), Chinook winds,

Temp inversion, convection of ocean, mantle

Second Law

e.g., electric power plant (steam), run at superheated steam, 700 K = Thot; 300 K == Tcold; e=400/700 ~60% (actually, most are less, have e~35-45%)

e.g. automobile e (using gasoline) ~ 26% to mechanical (electric cars, ~90%(?), but then times the 40% at the power plant - still, far less pollution))

Heat engine (heat to work: cyclic) - Heat flow always hot to cold, for engine, always have heat rejected, ideal efficiency e=(Thot-Tcold)/Thot (T in kelvins)- the best one can do.

Entropy

a measure of "disorder" - 2nd law says universe tending towards greater entropy.

Review Chapters 12-14

In essence, these chapters teach us that all matter is composed of atoms held together by electrical forces. All materials exist as solids, liquids or gases given the right conditions. Solids are held most tightly; as heat is applied, the solid melts and becomes liquid, and as heat is applied further, it becomes gas. All materials can be characterized by their density (greatest for solids, least for gases) Solids can be in compression or tension. Liquids and gases can only undergo compression, and do not support tension. A important concept for both liquids and gases is pressure (force/area) and buoyancy (uplifting force equal to weight of displaced fluid.) Pressure is the same at the same height in either a liquid or a gas. Additional pressure applied is transmitted uniformly through the fluid. In Ch 15 we find both solids and liquids expand some with increase in temperature, but resist compression. However, gases change their volume greatly with changes in temperature or pressure (V ~ T/P, where T measured in kelvins). Bernoulli's principle says that a gas has reduced pressure perpendicular to the direction of increased velocity of flow.

Review Ch 16-18

The subject of heat and thermodynamics studies another from of energy. Central to these studies are the First Law, the Second Law, the concept of entropy, and the relationship of heat and work (and efficiency).

October 14: Chapter 19 - Vibrations and Waves

Quiz, parts 2 &3 today

For next time, read Chapter 20.Sound and Chapter 21, Musical Sounds. (There are no Practicing Physics pages for Chapter 21

Simple harmonic motion (SHM)

"sine wavelike motion" wavelength, frequency, period

frequency (cycles/sec)= number of cycles (or "shakes" or vibrations) per second

unit: call cycles per second = hertz; e.g., ac current = 60 cycles per second = 60 hertz. KQED at 88.5 MHz (megahertz) = 88.5 million cycles per second)

period = T = time for one shake or cycle = inverse of frequency (= 1/f : seconds per cycle)

amplitude – size of vibration

restoring force, causes "oscillations" e.g., pendulum, spring and weight.

Waves - Like SHM in motion

speed (or velocity) of wave = distance / time; wavelength - distance wave goes in one period; if wave travels one wavelength, v = l /T = l f, the basic equation for waves v = l f, use l (greek "lambda")

Vibrations of waves: Transverse, Longitudinal

Refraction

Change of speed as cross boundary, e.g. from air into glass

Interference

Waves recombine with self - e.g. max and minima from two speakers, or combining with reflection

Constructive or destructive

Standing waves - interference - nodes (where cancel) and antinodes

Diffraction

Waves "bend" some around corners.

Bow wave, shock waves

Doppler effect

Speed of waves:

Sound, v ~ 340 m/s ~

Light (more later) v = 3.00 X 108 m/s

All waves (sound, light, water, etc.) refract, diffract, interfere

October 19: Chapter 20 - Sound & Chapter 21 - Musical Sounds: end part 4

Read Chapter 22 and the review questions. As always, do the Chapter- associated Practicing Physics pp75-76, (don't forget to go to Webassign for the HW exercises and problems.)

Highlights

Compression waves, 330 m/s

Resonance,

Sympathetic vibrations, beats

Forced vibrations

Natural frequency

Pitch, timbre

Frequency, "quality", harmonics

"Intensity"

energy per unit area, bels, decibels, logarithmic scale (powers of 10) Painful - 1 W/m2 = 120 dB; just audible 10-12 W/m2 = 0 dB, conversation ~ 60 dB, loud traffic ~70-80dB.

Loudness subjective, not the same as intensity

Sonar, ultrasound

 

October 21: Finish Sound, if needed; Chapter 22 - Electrostatics

Assignment Read Chapter 23, Electric Current. Do Practicing Physics pp77-79 (don't forget to go to WebAssign for the HW exercises and problems.) (this is a complicated and important chapter and set of exercises in the practicing physics pages: we'll finish these next time)

Highlights

Electrical Forces, Electrical Charge

Atoms, electrons, coulombs, conservation of charge

Coulomb's Law - ~q1q2/r2

Cf. Newtons Law of Gravitation

Insulators, conductors

Cf. Heat transfer

Charging, transfer of charge

Charging by induction

Differences between conductors, insulators

The Electric Field (and differences with gravitational field)

"alteration of space"

From (+) to (–)

Conductors shield, insulators change

The Electric Potential

Potential energy per unit charge - "voltage

joule/coulomb = volts

field - measured by volts/meter

Capacitor - stores (+), (-) charge at potential difference

volts X coulombs = joules

battery - converts chemical energy into separated charge at potential difference; again, coulombs X volts = joules

October 26: Chapter 23 - Electric Current

Do Practicing Physics pp80-84 (Chapter 23); Read Chap 24 (don't forget to go to WebAssign for the HW exercises and problems.)

Highlights

Charge flow: Coulombs/sec = amperes "conventional" à + to –

Electrical pressure à electric potential: volts

Voltage sources: batteries, generators, power supplies,

Closed circuit, Speed of electron flow, of electrons

Ohm’s Law: Current ~ Voltage/Resistance: I = V/R (amps = volts/ ohms)

Comments on electric shock – heart electrical pattern, destruction of nervous system Body resistance ~ 102 – 106 W

Potential difference: biological, shock, language

Dirct vs. alternating current (DC, AC),

Alternating voltage : Household 120 V avg.

conversion

Power

Voltage times current; watts = amps X volts

Series, parallel circuits
House circuits often 15 amps (1500 watts/110 volts = 14 amps)

Examples

October 28: Chapter 24 -- Electric Current(concldd) Magnetism

Assignment Read Chap 25 Do Practicing Physics pp 85-88(don't forget to go to WebAssign for the HW exercises and problems.)

Highlights

N, S poles

All magnets have both

N = "north-seeking" points to North, etc.

Opposites attract, like repel

Magnetic fields

Domains

Source – electrons in "orbits", electric currents

Electromagnets

Forces on moving charges

Electric Motors

Earth’s field

Probably due to currents in core.

Shields us from high energy particles emitted by sun

(picture of recent solar flare see sohowww.nascom.nasa.gov/hotshots/X17)

Selection of great (!) aurora pictures as a result of above, see
http://www.spaceweather.com/aurora/gallery_31mar01.html

November 2: Chapter 25 - Electromagnetic Induction,

Assignment Read Chap 26 Do Practicing Physics pp 89-90, (don't forget to go to WebAssign for the HW exercises and problems.) MC Quiz next Tuesday, parts 4-5, Ch 26

Highlights

Field lines (or flux) cutting wire - induces current

Demo: "induction coil"

Rotate coil in field = generator (produces voltage)

Max voltage - right angles between field lines and movement of wire.

Transformers (coupled flux)

Couple changes of flux (recall flux = field through an area)

if ac in one, changing flux in other, produces voltage.

Voltage/# of turns)A = Voltage/# of turns)B

or

NA / NB = VA / VB

But power (VI) remains constant.(energy conservation)

Power transmission - Hi V , Lo I

VI - constant, so use high V, low I, so have less heating loss in wires (I2R). Usually 10.4 kV to transformer by house, hundreds of thousands of V for cross country transmission, 220 V into house

 

 

November 4: Chapter 26 - Properties of Light

MC Quiz next Tuesday, Parts 4 & 5 and Chap 26

Assignment: Read Chapter 27, do Practicing Physics pp. 91-92 (don't forget to go to WebAssign for the HW exercises and problems.)

A great (and fun) web site for this chapter (see extra credit below, also)

http://www.phy.ntnu.edu.tw/~hwang/color/color_e.html

Extra Credit

Do the Tutorial on Color at Physicsplace, turn in a description of what you did and how it worked out.(this is a very good one)
Or go to
http://www.phy.ntnu.edu.tw/~hwang/color/color_e.html (this presents material similar to the Physicsplace site), go through the Exercises there and report.
Highlights

Electromagnetic waves

Changing magnetic field produces changing electric, vice versa -

Velocity = c = 3 X 108 m/s = velocity of light

In 1 cycle at 1 GHz (1x 109 ); period = 10-9 s, d = 3 x 108 m/s x 10-9 s = 0.3 m, size of a computer; or, distance light travels in a nanosecond = 30 cm.; in a microsecond = 300 m, etc.

EM spectrum -

radio (meter to 100's of meters), microwaves (fractions of m down to millimeters), infrared (millimeters to microns (10-6 m)), visible light (10-6 to 10-7 m), ultraviolet (10-7 to 10-9 m), x-rays (10-9 m to 10-11 m ), "gamma rays" (10-11 m to ??)

Transparent vs. opaque materials:

ties to vibrations of electrons in atoms.

Shadows, sharp and diffuse,
Shadow from sun: Umbra, penumbra

Metallic reflection - vibrations of electrons.

The eye

Optical illusions: go to (!!!)http://www.eyetricks.com or
http://dragon.uml.edu/psych/illusion.html

 

November 9: Chapter 27 - Color

(MC Quiz today) Assignment: Read Ch 28, Reflection and Refraction. Do Practicing Physics pp. 93 --104 (this is a long but very informative set), (don't forget to go to WebAssign for the HW exercises and problems.)

Highlights

Selective reflection and transmission

Mixing colored light and colored pigments

Additive and Subtractive, Complementary colors

Some color phenomena

Red Sunsets

Blue sky

White Clouds

Blue-Green water

 

November 11: Chapter 28 - Reflection and Refraction

Assignment: (for do for next time, but turn in at next quiz date

Read Chapter 29, Light Waves. Do Practicing Physics pp 105-108, (don't forget to go to WebAssign for the HW exercises and problems.)

Highlights (the link to the simulations relevant to today is

http://www.phys.hawaii.edu/~teb/optics/index.html

Reflection -

equal angles, virtual image, plane, concave and convex mirrors, reflection from diffuse and polished surfaces.

Refraction -

Light bending as moves obliquely from different speed media.

Basis for lenses.

Dispersion

Different speeds for different wavelengths in some media. Cause of separation of colors by a prism and by rainbows

Total internal reflection

Since light from lower speed media bends away from perpendicular, at some angle there's no room (fig 27.36).

Prisms in binoculars

Optical fiber "light pipes."

Lenses

Image formation

November 16: Chapter 29 - Light Waves

Assignment:

Read Chapter 30 and start 31. Do Practicing Physics pg109 (Due with pg. 110 for Ch 33) (don't forget to go to WebAssign for the HW exercises and problems.)

and go to http://www.colorado.edu/physics/2000/quantumzone/, navigate around the site, and for extra credit, write a page on the interactive demos you looked at (including the spectral signatures interactive demo).

Highlights

Huygen's principle -

that any element of a wave front can be viewed as generating new spherical waves that add to give new wave fronts. Allows explanation of diffraction, interference.

Diffraction

Waves bend around a barrier (Fig 28.7), spread when going through a slit. The longer the wavelength the greater angle of bending (explains why one hears sound waves behind a wall between you and speaker, e.g.)

Interference

Constructive and destructive addition of waves, produces "interference fringes."

Interference colors

When white light passes through a thin film (such as reflecting from water with an oil film on top - the thin film, see colors as a result of some waves adding, others canceling.

Polarized light

Direction of light vibrations, absorption of one, polarization of skylight, light by strained materials.

November 18: Chapter 30 - Light Emission, (bring a trash CD to use as a diffraction grating) Chapter 31 - Light Quanta (start)

Assignment

Finish Ch 31, Read Ch32. Do Practicing Physics pg110

Ch 30Highlights

Atoms: excitation, emission of radiation.

Phenomena:

Emission spectra, absorption spectra, Fluorescence, incandescence, phosphorescence, lasers

Chapter 31 - Light Quanta

Assignment

Finish Ch 32. Practicing Physics pg 111-112; First Reading Ch 33, do Practicing Physics p 111-112, (don't forget to go to WebAssign for the HW exercises and problems.)

Highlights, Ch 31

Birth of the Quantum theory

Quantization and Planck's Constant

Photoelectric Effect, the photon

Wave Particle duality

Double Slit Experiment

Waves as Particles Wave-

Particle Duality

The double slit experiment

Uncertainty Principle

Complementarity

November 23: Chapter 32, The Atom and the Quantum

Highlights

Ch 32 Atomic Spectra, Bohr model, relative sizes, Explanation of quantized levels, Quantum mechanics, particles as waves, Complementarity

Electron Waves and Quantum Mechanics

Explanation of quantized levels, particles as waves standing waves in atom.

Probability description of electron, etc.

Correspondence Principle

November 25-28: Thanksgiving Holiday

November 30: Finish Chapter 32, : Chap 33 - The atomic nucleus, radioactivity

Read Ch 34, do Practicing Physics pg 113 (don't forget to go to WebAssign for the HW exercises and problems.)

Highlights

Radioactivity

x-rays, alpha, beta, gamma rays

Effects of Radioactivity

Dosage and exposure

Discovery of the Atomic Nucleus

Rutherford's experiments

Atomic spectra

Bohr model

Relative sizes

The Nucleus (Isotopes, nuclear stability, half-lifes, natural transmutation, artificial transmutation, carbon dating)

Atomic number, atomic mass number

Half-lifes, carbon dating

p's and n's, short range force and coulomb repulsion

combinations, stability and decay Transmutation

natural transmutation, artificial transmutation,.

Nucleons, quarks

Elementary Particles

Leptons (e, v) quarks (u,d): lowest energy combination of quarks (p,n)

The nucleus

kinds of changes of nucleus, driving force and mass-energy equivalence E=mc2

chain reactions

Basics of a fission reactor

Plutonium

December 2: Chapter 34, Nuclear Fusion and Fission

Assignment: Review your work and quizzes for questions for next time class review

There will be a Quiz next time covering Ch's 27-34

 

Extra Credit

Copy, fill in, and turn in copies (keep a copy for study) the sample quizzes for parts 1-7

These will not be graded, but doing them will give extra credit pints towards your quiz grade - to get credit,you need to have done all the quizzes for parts 1-7.

We will go over the questions briefly in response to your questions.

Highlights

The nucleus

p's and n's, short range force and coulomb repulsion

combinations, stability and decay

chain reactions

driving force and mass-energy equivalence E=mc2

The basic curve of nuclear stability

Nature ALWAYS seeks lowest energy state!

Nuclear Reactions, cont.' - Fission and Fusion

Nuclear forces - contact attraction, charge repulsion

92235U and 94239Pu; U(238) à U(239) à Np(239) à Pu(239) (breeding)

Basics of a fission reactor

Elementary Particles

Nucleons, quarks (u,d à p,n); Leptons fa(electrons, neutrinos)

December 7: Modern Physics wrap-up, Quiz Ch 27-34: Bring Zeus form!

Highlights:

Review, final preparation

Review your work and quizzes for questions for class review

DON'T FORGET TO BRING A ZEUS FORM TO THE FINAL!

:wrap-up review(bring ZEUS form)

Review

Go over last quiz, answer questions, anything left over to do

 

December 9: course wrap-up (Dec 10: Last day of instruction for semester)

Dec 14: Final Exam: 1045 – 1315, Room Sci 201:


Don't forget to bring a full page Zeus form and a pencil.