20100430

Astronomy quiz question: contradicting the monolithic collapse model

Astronomy 210 Quiz 6, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

The monolithic collapse model is contradicted by which recent observation(s)?
(A) The sun has metal absorption lines.
(B) Not all globular clusters have the same age.
(C) Globular clusters with randomly tipped, elliptical orbits.
(D) The presence of dark matter in the halo.

Correct answer: (B)

According to the monolithic collapse model, material in the Milky Way had a spherical distribution, and the first generation of stars were born in globular clusters. These globular clusters were left behind in the halo of the Milky Way as matter collapsed into a thin disk. With no new material left in the halo, the only new star formation is in the disk of the Milky Way, which have higher metallicity, being made from the remnants of earlier massive stars.

Response (B) contradicts the monolithic collapse model, as it is expected that all globular cluster stars would only have formed before the collapse of material in the current disk of the Milky Way.

Response (A) is consistent with the monolithic collapse model, as is (C). Response (D) is a true statement that does not explicitly contradict the monolithic collapse model.

Section 30676
(A) : 4 students
(B) : 37 students
(C) : 18 students
(D) : 11 students

"Success level": 57% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.62

20100429

Astronomy quiz question: metal rich vs. metal poor stars

Astronomy 210 Quiz 6, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

Older stars are metal poor, while newer stars are metal rich because:
(A) metals produced by older stars were released by supernova explosions, and became part of newer stars.
(B) dark matter gradually converts metal rich stars into metal poor stars.
(C) older stars concentrate more of their metals into their cores, leaving their outer layers metal poor.
(D) older stars have had more time to break down heavy elements into lighter elements.

Section 30674
(A) : 30 students
(B) : 1 student
(C) : 6 students
(D) : 5 students

Correct answer: (A)

Stars produce metals (elements heavier than hydrogen and helium) in their cores during their giant/supergiant phases, up through type Ia/II supernovae explosions. Along with their unused hydrogen, these metals are then scattered into the interstellar medium, which are then incorporated into later generations of stars. An old, early generation star will have metals only in its core, while a young, later generation star will have metals sprinkled in its outer layers.

This was asked in Fall semester 2008 as a quiz question, and a final exam question.

"Difficulty level": 74% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.03

20100428

Astronomy quiz question: density wave theory

Astronomy 210 Quiz 6, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

According to the density wave theory, a gas cloud forms new stars as it passes through a spiral arm because:
(A) it slows down and compresses.
(B) it gathers more interstellar material.
(C) it will collide with dark matter.
(D) its metals will break down into non-metals.

Correct answer: (A)

According to the density wave theory, a gas cloud passing through a spiral arm does not collect new material to make new stars, but compresses as it encounters a "traffic jam" located there, which triggers new star formation.

Section 30674
(A) : 31 students
(B) : 3 students
(C) : 1 student
(D) : 2 students

Success level: 76% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.45

This question was asked in Fall semester 2009 as a quiz question.

20100427

Astronomy quiz question: exploded star still visible

Astronomy 210 Quiz 6, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

The __________ makes it possible for a massive star that has already exploded as a type II supernova to still be observed as a supergiant in Earth's night sky.
(A) Hubble law.
(B) early inflation of the universe.
(C) expansion of space.
(D) finite speed of light

Correct answer: (D)

Due to its finite, light from the type II supernova will take time to reach Earth, such that it may have already exploded, but light from its earlier supergiant phase is still traveling towards Earth.

Section 30674
(A) : 10 students
(B) : 1 student
(C) : 2 students
(D) : 29 students

"Success level": 71% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.38

Section 30676
(A) : 8 students
(B) : 2 students
(C) : 5 students
(D) : 55 students

"Success level": 81% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.30

20100426

Online reading assignment question: terrestrial planet tags

Astronomy 210 Reading Assignment 12, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

100421-terrestrialplanetwordle
http://www.flickr.com/photos/waiferx/4521406761/
Originally uploaded by Waifer X

Wordle.net tag cloud for "favorite terrestrial planet" generated by responses from Astronomy 210 students at Cuesta College, San Luis Obispo, CA, spring semester 2010 (http://www.wordle.net/show/wrdl/1932120/Untitled).

Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

Name your favorite terrestrial planet in our solar system. (Graded for completion.)

[Responses have been edited to consolidate related common subjects.]

Student responses
Sections 30674, 30676
Mars
saturn
earth
earth!
pluto
Saturn
venus
EARTH
Earth
Neptune
zertus
Earth
Earth
Earth
Venus
Pluto
Mars
Earth
earth duh
Saturn
mars
Pluto
Pluto
mars
Earth
Earth
Jupiter
no idea...
Earth
earth
Earth
jupiter
Earth
jupiter
Mars
Mercury
pluto
neptune
Mars
jupiter
Uranus
Besides earth? Mars I suppose.
Saturn
Mars
Pluto.
Mars
earth
neptune
mercury
saturn
Uranus ;)
Earth
Mars
Neptune
earth
earth
jupiter?
earth
Mars
Earth
Earth
saturn
Mars
earth?
uranus
I like Earth, I want to stay here.
Earth
Earth
I don't know...
Mercury
Mars
pluto
Venus
EE-Arth
Earth
Earth
Earth
Mercury
EARTH!
Earth
Saturn
Saturn
Venus
Earth
I'm gonna go with Earth
neptune
Earth
Saturn

20100425

Physics quiz question: step-up transformer

Physics 205B Quiz 6, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 20.34

The primary coil of a transformer has 400 turns; the secondary coil has 1000 turns. An alternating current is sent through the primary coil. The emf in the primary has an amplitude of 17 V. What is the emf amplitude in the secondary?
(A) 6.8 V.
(B) 10 V.
(C) 26 V.
(D) 43 V.

Correct answer: (D)

The transformer voltage equation is:

E_2/E_1 = N_2/N_1,

such that:

E_2 = N_2*E_1/N_1 = (1,000 turns)*(17 V)/(400 turns) = 42.5 V,

or 43 V, to two significant figures.

Response (A) is E_1*N_1/N_2; response (B) is E_1*(N_2 - N_1)/N2; response (C) is E_1*(N_2 - N_1)/N1.

Student responses
Section 31988
(A) : 2 students
(B) : 0 students
(C) : 0 students
(D) : 11 students

Success level: 84%
Discrimination index (Aubrecht & Aubrecht, 1983): 0

20100424

Physics quiz question: magnetic field of wire

Physics 205B Quiz 6, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 19.65

Consider a long straight wire that carries a current of 1.5 A. What is the magnitude of the magnetic field at the location shown, 0.20 m below the wire?
(A) 1.5e-6 T.
(B) 4.7e-6 T.
(C) 9.4e-6 T.
(D) 1.9e-5 T.

Correct answer: (A)

The magnitude of the magnetic field of a wire with current I is given by:

B = mu_0*I/(2*pi*r),

where mu_0 = 4*pi*10^7 T*m/A is the vacuum permeability, and r is the distance from the center of the wire, such that:

B = (4*pi*10^7 T*m/A)*(1.5 A)/(2*pi*(0.20 m)) = 1.5e-6 T.

Response (B) is mu_0*I/(2*r); response (C) is mu_0*I/r; response (D) is 2*mu_0*I/r.

Student responses
Section 31988
(A) : 12 students
(B) : 0 students
(C) : 0 students
(D) : 1 student

Success level: 92%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.20

20100423

Physics quiz question: charge moving through magnetic field

Physics 205B Quiz 6, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

[Version 1]

Consider an electron moving to the right at a through a uniform magnetic field. Increasing the speed of the electron (along the same direction) would __________ the magnitude of the magnetic force exerted on it.
(A) decrease.
(B) have no effect on.
(C) increase.
(D) (Not enough information is given.)

Correct answer: (C)

The magnetic force exerted on a moving charge is given by:

F_B = q*v*B*sin(theta),

where the angle between the charge velocity, and the magnetic field is 90 degrees, such that sin(theta) = 1, thus:

F_B = q*v*B.

Increasing the speed of the electron would increase the magnitude of the magnetic force on the electron.

Student responses
Section 31988
(A) : 3 students
(B) : 0 students
(C) : 5 students
(D) : 0 students

[Version 2]

Decreasing the speed of the electron (along the same direction) would __________ the magnitude of the magnetic force exerted on it.
(A) decrease.
(B) have no effect on.
(C) increase.
(D) (Not enough information is given.)

Correct answer: (A)

Student responses
Section 31988
(A) : 1 student
(B) : 1 student
(C) : 3 students
(D) : 0 students

Success level: 46%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.75

20100422

Astronomy current events question: Spirit incommunicado

Astronomy 210L, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

Students are assigned to read online articles on current astronomy events, and take a short current events quiz during the first 10 minutes of lab. (This motivates students to show up promptly to lab, as the time cut-off for the quiz is strictly enforced!)
John Antczak, Associated Press, "Hayabusa Hits the Homestretch," March 30, 2010
http://news.yahoo.com/s/ap/20100401/ap_on_sc/us_sci_mars_rover
According to NASA's Jet Propulsion Laboratory, the Mars rover Spirit failed to make a scheduled communication because it:
(A) is covered by dry ice (carbon dioxide) snow drifts.
(B) shut down for safety during a marsquake.
(C) is still processing a software upgrade.
(D) was drilling a hole into the core of a meteorite.
(E) does not generate enough power from its dust-covered solar panels.

Correct answer: (B)

Student responses
Sections 30679, 30680
(A) : 4 students
(B) : 2 students
(C) : 5 students
(D) : 0 students
(E) : 27 students

20100421

Astronomy current events question: Hayabusa mission near completion

Astronomy 210L, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

Students are assigned to read online articles on current astronomy events, and take a short current events quiz during the first 10 minutes of lab. (This motivates students to show up promptly to lab, as the time cut-off for the quiz is strictly enforced!)
Kelly Beatty, "Hayabusa Hits the Homestretch," March 30, 2010
http://www.skyandtelescope.com/news/89510417.html
After many setbacks, the Japan Aerospace Exploration Agency Hayabusa spacecraft is planned to complete its mission, which is:
(A) landing on and burrowing into the core of a comet.
(B) bringing to Earth samples scraped off an asteroid.
(C) delivering a rover onto the surface of Mars' moon, Phobos.
(D) unfolding and using solar sails to travel to Jupiter's moon, Europa.
(E) proving ion engines can be used for interplanetary travel.

Correct answer: (B)

Student responses
Sections 30678, 30679, 30680
(A) : 1 student
(B) : 51 student
(C) : 5 students
(D) : 1 student
(E) : 2 students

20100420

Astronomy current events question: Pac-Man Mimas

Astronomy 210L, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

Students are assigned to read online articles on current astronomy events, and take a short current events quiz during the first 10 minutes of lab. (This motivates students to show up promptly to lab, as the time cut-off for the quiz is strictly enforced!)
Astronomy.com editors, "1980s Video Icon Glows on Saturn Moon," March 30, 2010
http://www.astronomy.com/asy/default.aspx?c=a&id=9714
Recent images obtained by NASA's Cassini spacecraft of __________ on Saturn's moon Mimas show a pattern resembling the 1980's video game icon "Pac-Man."
(A) surface temperatures.
(B) computer-enhanced colors.
(C) organic compound concentrations.
(D) ancient versus recent lava flows.
(E) surface reflectivity/absorption.

Correct answer: (A)

Student responses
Sections 30678, 30679, 30680
(A) : 48 students
(B) : 3 students
(C) : 6 students
(D) : 3 student
(E) : 0 studentss

20100419

Online reading assignment question: big bang tags

Astronomy 210 Reading Assignment 11, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

100414-bigbangwordle
http://www.flickr.com/photos/waiferx/4521406761/
Originally uploaded by Waifer X

Wordle.net tag cloud for "big bang" generated by responses from Astronomy 210 students at Cuesta College, San Luis Obispo, CA (http://www.wordle.net/show/wrdl/1901639/Untitled). Compare with similar results from Fall semester 2009.

Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

Write down five words that describe or are associated with the "big bang." Keep word phrases together with no spaces between them (e.g., "forexample, likethis, nospaces"). (Graded for completion.)

[Responses have been edited to consolidate related common subjects.]

Student responses
Sections 30674, 30676
myspace, facebook
averyloundsound, boom
theory, nonreligious, beginningoftime
notime, blackhole, infinitedensity, point, beginning
God, stars, theory, big, boom
explosion, fun, glitter, hot, curious
evolution, stars, universe, life, creation
bang, star, space, moon, screw
formationofhelium, universebegan, expandingdough, rasinbread, hotgas
atoms, theory, formation, television, God
stars, blackhole, universe, galaxy, bright
paradox, cosmology, expandinguniverse, FredHoyle, sciencefiction, TVshow
boom, universe, GeorgesLemaitre, blackbodycurve, redshift
theory, universe, explosion, expanding, space
scary, hot, end, beginning, future
higgsboson, hadroncollider, theGodparticle, howtheuniversewasformed, photonsmashing, plasmasoup
TVshow
dirtythings, stars, planets, matter, space
cool, bright, random, weird, unknown
nothing, explosion, pop, dumb, sudden
explosion origin redshift, blueshift
dinosaur, meteor, Earth, extinction, theory
creation, stars, explosion, massive, newbeginning
universe, galaxies, cosmic, darkmatter, darkenergy
Earth, bigbang, space, beginningofEarth, craziness
big, giant, huge, enormous, bang
big, boom, explosion, particles, life
explosion, dust, time, loud, formation
sun, Earth, explode, fun, interesting
14billionyearsago, continualexpansion, globularclusters, darkmatter, bigcrunch
science, universe, planets, stars, space
beginningofexistence, largeexplosion, sciencybusiness, thingidontknowabout, iwanttoknowabout
boom, creation, explosion, life, stars
universe, atom, hot, dense, 14billionyearsago
singularity, hotsoup, silent, expansion, beginning
power, creation, explosion, impact, myth
Earth, God, universe, epic, huge
controversy, origin, universe, movement, directional
explosion, nova, gas, dust, starformation, planetformation
large, huge, awesome, massive, change
explosion, creation, bazinga, expansion, cataclysmicbirthoftheuniverse
beginning, expanding, scientificevidence, theory, cosmological
big, bang, controversial, scientific, astrological
gun, monkey, chance, stella, shoe
orgy, Earthscreation, big, bang, theory
bopom, pow, bam, bang, slam
explosion, goesagainstreligion, start, bigspace, universe
bang, beginningoftime, theory, creation, theendingofadamngooddate
explosion, beginning, elements, collision, creation
explosion, blowup, bomb, bang, light
beginning, universe, explosion, theory, fact
imnotsure
beginning, formation, explosions, gg, coolstorybra
begining, expansion, beforetherewasnothing, matter, infinite
centrifugalforce, strongforce, weakForce, fullofholes, cleverthinking
hot, everything, beginning, dense, crazyphysics
expansion, highdensity, temperature, hubbletime, galaxies
nothingbefore, createduniverse, explosion, supernova
boom, flash, bright, dirty, big
lotsofstarsgoboom
explosion, dust, ignition, power, gravity
itsanexpansionnotexplosion
expanding, universe, galaxies, began
evolution, cellappearance, evolvingspecies, lifebegins, stardistribution
what?
boom, bang, beginning, universe, space
big, explosion, newgeneration
continuouslyexpanding Hubbleredshift
beginning, burst, startoftime
expansion, explosion, beginning, universe, origin
dangerous, damage, huge, history, meat
physics, birthofuniverse, radiation, planet, world
explosion, boom, life, atmosphere, wow
beginning ,explosion, formation, Earth, everything
bigbang, universe, beginning, pastexistence, beforeandafter
creation, expansion, volume, space, matter
origin, theory, primordial, expanding, cosmologicalmodel
bigassexplosion, God, Creation, Evolution, nonsensical
bang theory nothingexplodes wtf
Genesis1:1, theory, false, excuse, origin
big, weird, crazy, outerspace, interesting
evolution, origins, supernova, 2012, collision

20100417

Found physics: step-up transformer

100410-1150326
http://www.flickr.com/photos/waiferx/4509302580/
Originally uploaded by Waifer X

Step-up transformer using RadioShack 273-104 snap-on RF choke as the soft-iron core, driven at 60 Hz. Photo by Cuesta College Physical Sciences Division instructor Dr. Patrick M. Len.

20100416

Student scribble: Galilean satellites, re-imagined

20100326502
http://www.flickr.com/photos/waiferx/4465839843/
Originally uploaded by Waifer X

Student reinterpretation of Galilean satellites, Astronomy 210L worksheet. Photo taken by Cuesta College Physical Sciences Instructor Dr. Patrick M. Len. Taken at 3:58 PM on April 02, 2010--uploaded by ShoZu.

20100326503
http://www.flickr.com/photos/waiferx/4487032908/
Originally uploaded by Waifer X

Student scribbles on Galilean satellites, Astronomy 210L worksheet. Photo taken by Cuesta College Physical Sciences Instructor Dr. Patrick M. Len. Taken at 3:58 PM on April 02, 2010--uploaded by ShoZu.

20100415

Student scribble: "Physics 205B Rules!"

20100326502
http://www.flickr.com/photos/waiferx/4465839843/
Originally uploaded by Waifer X

Student artwork posted on bulletin board in Room 2101, Cuesta College, San Luis Obispo, CA. Photo by Cuesta College Physical Sciences Division instructor Dr. Patrick M. Len.

20100414

Found physics: ferromagnetic paper clip, staples

20100325499
http://www.flickr.com/photos/waiferx/4463902740/
Originally uploaded by Waifer X

U-magnet, paper clip, and staples demonstration of ferromagnetism. Photo by Cuesta College Physical Sciences Division instructor Dr. Patrick M. Len.

20100413

Found physics: sun, through solar filter

100315-1150165
http://www.flickr.com/photos/waiferx/4508661381/
Originally uploaded by Waifer X

The sun, observed safely through a 14" solar filter, Bowen Observatory, Science Forum rooftop, Cuesta College, San Luis Obispo. Photo by Cuesta College Physical Sciences Division instructor Dr. Patrick M. Len.

20100412

Astronomy quiz question: pressure-temperature thermostat

Astronomy 210 Quiz 5, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

If the production of energy were to suddenly increase in the core of the sun, the pressure-temperature thermostat would restore it by __________ the size of the sun, which would __________ the pressure and temperature.
(A) increasing, increase.
(B) decreasing, increase.
(C) increasing, decrease.
(D) decreasing, decrease.

Correct answer: (C)

An increase in energy production would result in heating and expanding the size of the sun. Due to this adiabatic expansion, the pressure and temperature would decrease.

Section 30676
(A) : 6 students
(B) : 5 students
(C) : 44 students
(D) : 6 students

"Success level": 75% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.32

20100411

Astronomy quiz question: neutron star precursor

Astronomy 210 Quiz 5, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

A __________ main sequence star will eventually become a neutron star.
(A) massive.
(B) medium-mass.
(C) low-mass.
(D) (More than one of the above choices.)
(E) (None of the above choices.)

Correct answer: (B)

Massive main sequence stars can either become black holes or neutron stars, depending on the mass of the core remaining after the type II supernova explosion at the end of its supergiant phase.

Section 30676
(A) : 42 students
(B) : 10 students
(C) : 4 students
(D) : 4 students
(E): 1 student

"Success level": 72% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.63

20100410

Overheard: tricky and tricked

Astronomy 210, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

(Overheard in introductory astronomy lecture.)

(Students plotting locations of known stars at different distances from Earth's location in the Milky Way, and realizing that all these locations are only in the immediate vicinity, well within the same galactic spur, rather than spread out at varying distances across the Milky Way, as initially expected.)

Student: "Hey, y'know, that question was pretty tricky! But we totally got it now."

(Beat.)

Instructor: "It was only tricky if you were tricked."

(Beat.)

Student: "Yeah...okay. Now that deserves a fist bump."

20100409

Overheard: floating rocks

Astronomy 210L, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

Submerged crustal rocks
http://www.flickr.com/photos/waiferx/536539070/
Originally uploaded by Waifer X

(Overheard in introductory astronomy lab.)

(Students dropping rocks into a water-filled graduated cylinder, in order to determine their displacement volume.)

(Beat.)

Student: "Wait! Why aren't the rocks floating?"

20100408

Astronomy current events question: primitive supermassive black holes

Astronomy 210L, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

Students are assigned to read online articles on current astronomy events, and take a short current events quiz during the first 10 minutes of lab. (This motivates students to show up promptly to lab, as the time cut-off for the quiz is strictly enforced!)
Astronomy.com editors, "Astronomers Discover Most Primitive Supermassive Black Holes Known," March 18, 2010
http://www.astronomy.com/asy/default.aspx?c=a&id=9678
University of Arizona researchers have announced the discovery of two supermassive black holes, which are thought to be the most primitive known because of their:
(A) lack of dust.
(B) low masses.
(C) sharp edges.
(D) extreme blackness.
(E) monstrous size.

Correct answer: (A)

Student responses
Sections 30678, 30679, 30680
(A) : 48 students
(B) : 1 student
(C) : 4 students
(D) : 1 student
(E) : 8 students

20100407

Astronomy current events question: smarter Opportunity rover

Astronomy 210L, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

Students are assigned to read online articles on current astronomy events, and take a short current events quiz during the first 10 minutes of lab. (This motivates students to show up promptly to lab, as the time cut-off for the quiz is strictly enforced!)
Astronomy.com editors, "Mars Rover Getting Smarter As It Gets Older," March 24, 2010
http://www.astronomy.com/asy/default.aspx?c=a&id=9693
NASA's Mars Exploration Rover Opportunity is now able to choose and investigate targets on its own, without constant human monitoring, due to:
(A) rebooting its memory.
(B) unexplained reasons.
(C) a software upgrade.
(D) transferring data to the unused Spirit rover.
(E) an evolution in artificial intelligence.

Correct answer: (C)

Student responses
Sections 30678, 30679, 30680
(A) : 2 students
(B) : 1 student
(C) : 46 students
(D) : 9 students
(E) : 5 students

20100406

Physics quiz question: contact-shorted battery

Physics 205B Quiz 5, spring semester 2010
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 18.95(a)

"20100220488"
Waifer X
flic.kr/p/7EusJt

A Physics 205B student accidentally touches the terminals of an ideal battery with an emf of 67.5 V, and experiences a tingling sensation from 0.50 mA of current. The resistance of the student is:
(A) 34 Ω.
(B) 1.4×102 Ω.
(C) 3.4×104 Ω.
(D) 1.4×105 Ω.

Correct answer (highlight to unhide): (D)

From Ohm's law,

I = ΔV/R,

such that solving for R,

R = ΔV/I = (67.5 V)/(0.50×10–3 A) = 1.35×105 Ω,

or 1.4×105 Ω, to two significant figures.

Section 31988
Exam code: quiz04v0L7
(A) : 1 student
(B) : 1 student
(C) : 1 student
(D) : 7 students

Success level: 70%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.25

20100405

Physics quiz question: charging capacitor

Physics 205B Quiz 5, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 18.83

An ideal 15 V emf source connected to an ideal 70 kiloohm resistor and a 12 µF capacitor. The switch is closed at t = 0. At what time t will the voltage across the capacitor be 10 V?
(A) 0.28 s.
(B) 0.34 s.
(C) 0.56 s.
(D) 0.92 s.

Correct answer: (D)

For a charging capacitor, the potential difference across the capacitor as a function of time is given by:

delta(V) = emf*(1 - exp(-t/(R*C)),

such that solving for t:

t = -R*C*ln(1 - emf/delta(V)),

where the quantity inside the natural logarithm is (1 - emf/delta(V)) = (1 - (10 V)/(15 V)) = 1/3, thus:

t = –R*C*ln(1/3) = -(70e3 ohms)*(12e-6 F)*ln(1/3) = 0.922834322 s = 0.92 s.

Response (A) is (1/3)*R*C; response (B) is -R*C*ln(2/3); and response (C) is (2/3)*R*C.

Student responses
Section 31988
(A) : 0 students
(B) : 4 students
(C) : 6 students
(D) : 0 students

Success level: 0%
Discrimination index (Aubrecht & Aubrecht, 1983): 0

20100404

Physics quiz question: US vs. European electricity

Physics 205B Quiz 5, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Comprehensive Problem 18.113(d)

An 800 W room heater from Europe that plugs into a 240 V outlet is brought back home by a Physics 205B student, (somehow) plugging it into a 120 V outlet. How much power would the room heater use?
(A) 100 W.
(B) 200 W.
(C) 400 W.
(D) 680 W.

Correct answer: (B)

Assuming that the resistance of the heater remains constant, then the current used when plugged into a 120 V outlet is:

I_US = delta(V_US)/R = (120 V)/R = (1/2)*(240 V)/R = (1/2)*I_Europe.

Then the power used by heater when plugged into a 120 V outlet will be:

P_US = I_US*delta(V_US) = (1/2)*I_Europe*(1/2)*(V_Europe) = (1/4)*P_Europe = 200 W.

Response (A) is (1/8)*P_Europe; Response (C) is (1/2)*P_Europe; and response (D) is P_Europe - delta(V_US).

Student responses
Section 31988
(A) : 0 students
(B) : 0 students
(C) : 7 students
(D) : 3 students

Success level: 0%
Discrimination index (Aubrecht & Aubrecht, 1983): 0

20100403

Astronomy current events question: Gliese 710 close approach

Astronomy 210L, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

Students are assigned to read online articles on current astronomy events, and take a short current events quiz during the first 10 minutes of lab. (This motivates students to show up promptly to lab, as the time cut-off for the quiz is strictly enforced!)
Kelly Beatty, "Future Shock From Gliese 710," March 17, 2010
http://www.skyandtelescope.com/news/home/88198587.html
According to researchers, what is predicted to happen when the star Gliese 710 passes 1.3 light years from the sun roughly 1.5 million years from now?
(A) A slight increase in comet impacts on Earth.
(B) Disruption of Earth's orbit around the sun.
(C) A small probability that a binary star system will form.
(D) Massive tides on Earth.
(E) The night sky will no longer be dark enough to see other stars.

Correct answer: (A)

Student responses
Sections 30678, 30679, 30680
(A) : 16 students
(B) : 6 students
(C) : 2 students
(D) : 1 student
(E) : 1 student

20100402

Online reading assignment question: Milky Way tags

Astronomy 210 Reading Assignment 10, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

100402-milkywaywordle
http://www.flickr.com/photos/waiferx/4485109813/
Originally uploaded by Waifer X

Wordle.net tag cloud for "Milky Way," generated by responses from Astronomy 210 students at Cuesta College, San Luis Obispo, CA (http://www.wordle.net/show/wrdl/1862192/Untitled).

Students have a weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

Write down five words that describe or are associated with the "Milky Way." Keep word phrases together with no spaces between them (e.g., "forexample, likethis, nospaces"). (Graded for completion.)

[Responses have been edited to consolidate related common subjects.]

Student responses
Sections 30674, 30676
galaxy, system, grouping, space, awesome
yum, yum, yum, yum, caramel
cloudy, faint, asteroid, sky, band
starclusters, mainsequencestars
stars, planets, comets, blackholes, planetarynebula
chainofrocks, dirty, brightatnight, chunky, destructive
rotationcurve, diskcomponent, darkhalo
lotsofstarsandgalaxies
candy
stars, swirling, milkycircle, glowing, nuclearbulge
delicious, chocolatey, caramel, goodness, candy
reflectionnebula
milk, way, candy, space, stars
whenyourhavingasaddayitisnicetositbackandchompdownonamilkyway, lotsofstars, cloud9, galaxyconquest, godly
stars, planets, comets, asteroids, blackholes
deliciouslygoodchocolatecandybar
night, awesome, halo, visiblematter
candybar, stargroup, sprinkles
galaxy, supermassiveblackhole, spiralarms, Sagittarius, localgroup
candybar, galaxy, pretty, wavey, hazy
ourgalaxy, starclusters, sun, planets, disk
creamy, thick, rich, chocolate, decadence
chocolate, galaxy, stars, planets
galaxy, stars, constellation, night, centerofuniverse
milkyway, gravity, size, shape, darkmatter
bigglowingencirclingmilkyband
milkywhite, bigassgalaxy, candybar
wheellikestarsystem, galaxy, kuklos, vialactea, 100billionstars
stars, clusters, family, ours, pretty
ourgalaxy, stars, space, chocolate
milkyway, galaxy, road, candy
big, clusters, interesting, broad, ourgalaxy
theyarestarsclosetogether
chocolate, nova, supernova, eclipse, revolution, rotation
candybar, tasty, caramel, chocolate, otheryummystuff
chocolate, infinite, galaxy, nuttygoodness
nova, sparkles, blue, milky, beautiful
star, candy, galaxy, space, Earth
candy, starry, big, pretty, cosmos
candy, hungry, black, sky, heat
spiralshape, beautiful, wherewelive, glittery, yummycandy
densestarscluster, smear, heavens
galaxy, stars, candybar, space, faraway
expansive, visible, galaxy, stars, light
galaxy, stars, light, huge, visible
stars, dust, cluster, fast, easytosee
galaxy, spiral, vialactea, bandoflight, visibleuniverse
greatstarsystem, halo, rotationcurve, spiralarms, diskcomponent
galaxy, candybar, space, chocolate, astronomy
stars, gas, galaxy, spiral, light
galaxy, stellardisk, lightyears, spiralarms, distantstars
milky, smooth, chocolatecovered, candybar, fluffyfilling
galaxy, vast, quiet, bright, astros
candy, yummy, hunger, fat
starclusters, vialactea, ourgalaxy, cloudofstars, and spiralarms
thebestcandybarever
Jupiter, Earth,stars, moons, Uranus
swirl, star, bright, beautiful, chocolate
galaxy, candy, solarsystem, stars, planets
stars, dust, swirls, candybar, sky
chocolate, malt, nougat, carmel, fluff
galaxy, planets, candybar, sun, space
canteventhinkofoneidontreallygetit:/
particle, metals, debris, birthplace
candybar, stars, creamy, milk, flows
chocolate, reallyreallycool, whitestripe
galaxy, ours, big, pretty, cool
stars, candybar, milky, big, galaxy
Neptune, Earth, Venus, Mars, BigDipper
earth, sun, galaxy, moons, stars
chocolate, stars, alotofstars, stripeinthesky, galaxy
embellish, elements, dynamic, intelligent
milkycenter, light, stars, acrosssky, starblur, delicious
galaxy, space, neverending, blackhole
galaxy, spiral, southernsky, Orion
candy, chocolate, candy, rocks, big
galaxy, candybar, dairy, spiral
galaxy, nebula, hydrogen, stars, space
dark, colorful, circular, awesome,s tars
spiralarms, dust, gas, stars, bandoflight
barredspiral, stars, gas, dust, vialactea
starclusters, neutronstar, blackhole, home, nighttimesky
chocolate, delicious, sugary, treat, fat
candy, galaxy, tasty, beautiful, cool
candybar, galaxy, alcoholicdrink, haze, sexposition
circular, spirals, galaxy, stars, elliptical
candybar, jesusjuice, clustersofstars, funnycolors, itbefinghuge
galaxy, solarsystem, universe, planets, chocolate
sun, nuclearbulge, disk, globularcluster, halo
candy, stars, galaxy, solarsystem, dust

Astronomy current events question: Jupiter's Great Red Spot glowing

Astronomy 210L, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

Students are assigned to read online articles on current astronomy events, and take a short current events quiz during the first 10 minutes of lab. (This motivates students to show up promptly to lab, as the time cut-off for the quiz is strictly enforced!)
Astronomy.com editors, "Jupiter's Spot Seen Glowing," March 17, 2010
http://www.astronomy.com/asy/default.aspx?c=a&id=9673
Ground-breaking thermal images of Jupiter's Great Red Spot, revealing swirls of warmer air and cooler regions, were recently taken by:
(A) the Hubble Space Telescope.
(B) instruments attached to ground-based telescopes.
(C) the Galileo space probe.
(D) the Spitzer Space Telescope.
(E) instruments attached to the International Space Station.

Correct answer: (C)

Student responses
Sections 30678, 30679, 30680
(A) : 9 students
(B) : 8 students
(C) : 7 students
(D) : 5 students
(E) : 2 students

20100401

Astronomy quiz question: fusion-generated hydrostatic equilibrium

Astronomy 210 Quiz 5, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

The sun is able to support its weight and maintain a stable size by:
(A) means of strong convection currents.
(B) the radioactive decay of unstable elements.
(C) the resistance to compression of degenerate matter.
(D) generating energy from fusion.

Correct answer: (D)

Hydrostatic equilibrium demands that pressure supports weight, in order for the sun to maintain its stable size; this pressure is generated by the energy released from fusion in its core (as regulated by the pressure-temperature thermostat).

Section 30674
(A) : 3 students
(B) : 0 students
(C) : 6 students
(D) : 34 students

Note that response (B) refers to nuclear fission.

"Success level": 81% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.43

Astronomy quiz question: temperature and fusion

Astronomy 210 Quiz 5, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

[Version 1]

Nuclear fusion is unlikely to occur at room temperature, because nuclei would not move quickly enough to:
(A) break heavy elements apart.
(B) create convection currents.
(C) overcome gravity.
(D) overcome repulsion.

Correct answer: (D)

Atomic nuclei repel each other due to their constituent protons; this repulsion can only be overcome when the nuclei approach each other rapidly enough at temperatures much higher than room temperature.

Note that response (A) refers to nuclear fission.

Section 30674
(A) : 0 students
(B) : 3 students
(C) : 3 students
(D) : 37 students

"Success level": 87% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.24

[Version 2]

Nuclear fusion requires very high temperatures in order for nuclei to move rapidly enough to:
(A) overcome gravity.
(B) overcome repulsion.
(C) break heavy elements apart.
(D) create convection currents.

Correct answer: (B)

Section 30676
(A) : 3 students
(B) : 45 students
(C) : 6 students
(D) : 5 students
(Blank): 2 students

"Success level": 76% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.38

Astronomy current events question: first temperate exoplanet

Astronomy 210L, Spring Semester 2010
Cuesta College, San Luis Obispo, CA

Students are assigned to read online articles on current astronomy events, and take a short current events quiz during the first 10 minutes of lab. (This motivates students to show up promptly to lab, as the time cut-off for the quiz is strictly enforced!)
Astronomy.com editors, "First Temperate Exoplanet Sized Up," March 17, 2010
http://www.astronomy.com/asy/default.aspx?c=a&id=9675
Planet Corot-9b is considered the first exoplanet that resembles planets in our solar system. The French space agency CoRot satellite discovered this planet by __________ its host star.
(A) measuring temperature fluctuations of.
(B) detecting wobbles in the motion of.
(C) watching as it passes in front of.
(D) beaming radar signals that were reflected from around.
(E) observing the amount of light reflected by the planet from.

Correct answer: (C)

Student responses
Sections 30678, 30679, 30680
(A) : 8 students
(B) : 3 students
(C) : 24 students
(D) : 8 students
(E) : 6 students