Course: Physics 101, Conceptual Physics Fall 2003

This course attempts to give a broad introduction to the wonderful 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.

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.

August 28, September 2: Introduction (s), About Science

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

Read Chap 1 and 2 (particularly note review questions Chapter 2 #'s 4-7, 19-21, 25. These are not to be turned in) and fill out Practicing Physics pp. 1-pg. 4 and Exercises 2: 20, 22 (this means "Exercises chapfer 2 numbers 20 and 22). These are to be turned in at the time of the first quiz. They MUST be stapled.

For extra credit -

Text: Chapter 1 Project, p 18. 52 (turn in a brief half-page write-up, describing what you did and your results. This will apply to all the extra credit projects you might do.).

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 experimental behavior that always occurs
• Hypothesis

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

Theory

• - an explanation of a large group of group of facts and information that explains relationship AND can be tested for falsity.

Chapter 2 - Newton's First Law -Inertia

Assignment (for next time but turned in on the 11th):

Read Chapter 3 (N.B. RQ3: 2-4, 7-9, 10-11,16,18-19,24-26), Practicing Physics pp.. 5-6 and Exercises 3: 8, 26 (note the abbreviated notation I use, and that N.B. stands for Noto Bene, Latin for note well),

Extra Credit:

Project, p 52 (turn in a brief half-page write-up, describing what you did and your results). Or-view the Chapter 3 videos at Physicsplace, write a brief report <1 page, describing each video Or do Problems 3: 4, 6.

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.

September 4: Chapter 3 - Linear Motion

Assignment (for next time but turned in on the 11th)

Read Chapter 4, and note the review questions. Do Practicing Physics pp. 7 -10,the project 2, pg 66 and Problem 4:2.

Extra credit:

Do 2 of the remaining projects.

Or Do Problems 4: 7, 8.

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

September 9: Chapter 4 - Newton’s Second Law

Note: all homework to date(through Chapter5 due next time, and the whole set must be stapled, with each chapter in order Practicing Physics page, your pages of exercises and problems and then your extra credit (start extra credit on a separate piece of paper from the other work,or it may not get counted.)

Assignment:

Read Chapter 5, RQ's. Do PP pp11-17, and Exercise 8, 10 (careful here), 17

Extra credit:
Problem 5: 5, 6

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

Examples

September 11: Chapter 5 – Newton’s Third Law (Quiz today on Chapters 1-5, BE SURE TO BRING ZEUS FORM)

Assignment: (due at next quiz, not today)

Read Chapter 6, do Practicing Physics PP6:21-23), Exercise 6:1, 20, 29, 35; 43 Problem 6: 1, 2

Extra Credit

Do Problems 6: 5. 11

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

Examples

Components

Using right triangles

September 16: Chapter 6 - Momentum

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

Read Chapter 7, do Practicing Physics pp. 25-30 and Hewitt - Exercises 7:12, 25, 46, Problems 7: 2, 3, 5

Extra credit:

Do Problem 7: 6, 8, 10

Or (And /or) do Project 7:1 and 7:3(!), pg 121

Highlights, Chapter 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

September 18: Chapter 7 - Energy

Assignment:

Read Chapter 8, paying attention to the review questions (!) , esp 4,9,15,26,35

Do Practicing Physics :31à 36, Exercises 8: 1, 14,33,42,46; Problem 8: 5, 9

Extra Credit:

Problems 8: 2, 4, 6

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 23: Chapter 8 – Rotational Motion

("Big Quiz" on part 1 (through Chapter 10) next time. Don't forget Zeus form. Homework due next time, Don't forget to bring stapled assignments).

Assignment:

Read Chapter 9 and Chapter 10 (to pg 188 only); look at the review questions, esp. RQ 9: 6,7,9-11,14-18, 20; RQ10:1-17

Do Practicing Physics pp 37-45, , Exercises 9: 17, 37; Problem 9: 3 Exercises 10: 6, 49 , Prb 10: 1(careful), 4

Extra credit:

Do Problems 9: 2; 10: 6,7.

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 25: Chapter 9 - Gravity AND Chapter 10 Projectile and Satellite Motion; Review of Mechanics End part 1 (Big Quiz this time - part 1 thorugh Chapter 10: bring ZEUS form) (2nd Homework Set due.)

Assignment:

Read Chapter 11 AND Chapter 12; do Practicing Physics PP49-52, Exercises 11: 17, 20, 29; Problem 11: Exercises 12: 5, 16, 17, 30

Extra credit:

Problem 11: 2, 4 Problem 12: 6

Gravity

Gravitation

Newton’s Law of
Impact on culture
Fundamental force, shapes universe
Other fundamental forces, electromagnetic, nuclear strong, nuclear weak.

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

G = 6.7 x 10-11 N m2 /kg

Relationship to weight (F=mg), weightlessness.

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

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

Read Ch 13 and 14. Do Practicing Physics pp. 53-57 and Chapter 13, Ex. 5, Prblm 3, Ch 14 Ex. 25, Prblm 2

Extra Credit

Do problem 14: 2 and either:

Do the scaling tutorial at Physics Place, turn in a report on what you did (and learned)

And/or

Do and write a report on projects 13: 1- 3.
And/or

Projects 14: 1, 4, 5

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

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

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

Read Ch 15 Do Practicing Physics pp. 59-60 (there will be a "normal" quiz on this chapter) Do Exercises Ch15: 15, 20, Prblm 15: 2; Exercises 16: 15, 17, 40; Prblm 16: 6.

Start Reading Ch 16 (through about pg 313), do Practicing Physics pp. 61-62

Extra Credit

Do Problems 15: 1,4, 7; 16: 2.

High points:

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.

Oct 7: Chapter 15 Temperature, Heat, and Expansion; Start Chapter 16 - Heat Transfer

Quiz next time

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

Finish Ch 16, Read Ch 17, Do Practicing Physics pp. 63-65, RQ's 17: 3, 7, 16, 30 (this time the RQ's are to turn in.) Exercises s 17: 48; start Ch 18 (at least through pg 344),

Extra Credit

Do Problem 17: 1
And do one of the excellent and easy projects at the end of 17 and report as to what happened and why.

High Points, Chapter 15 and 16:

Temperature,

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

Heat -

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.

Oct 9: Finish Chapter 16- Heat Transfer; Chapter 17 - Change of Phase:

NO Quiz today, changed to nesxt Tuesday, but same chapters and same homework due., Chapters 12-17 (don't forget Zeus form)

Assignment

Read Ch 18 Look at the review questions. Do Practicing Physics pp. 67-68, Exercises 18: 4, 8, 10, 11, 25, 35 Problem 18: 2

Extra Credit

Problem18: 3, 6

Highlights

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

Water- 80 cal/gm melting; 540 cal/gm boiling

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.