P-dog's blog: boring but important: 201011

20101130

Astronomy midterm question: no center for universe?

Astronomy 210 Midterm 2, Fall Semester 2010
Cuesta College, San Luis Obispo, CA

[20 points.] An astronomy question on an online discussion board (http://answers.yahoo.com/question/index?qid=20100905145749AAyQLJr) was asked and answered:

Bell: What is at the center of the universe?

Stimpy: The universe is not defined to have [a] center. Wherever you are in the universe you will always appear to be in the center.

Discuss why this answer is correct, and how you know this. Explain using observations and evidence related to the Hubble law.

Solution and grading rubric:

p = 20/20:
Correct. Hubble's law is that the recession velocity of galaxies is proportional to distance, evidence is that there is a greater redshift of absorption lines for distant galaxies compared to nearby galaxies. This corresponds to the expansion of space between galaxies, such that each galaxy seems to be center of expansion as observed from their position. May use analogies as not-like-an-explosion, raisin bread, enlargement of between-spaces, etc.
r = 16/20:
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Discusses how Hubble's law expansion will be observed identically for all viewpoints, but does not explicitly discuss absorption line redshift evidence for Hubble's law.
t = 12/20:
Contains right ideas, but discussion is unclear/incomplete or contains major errors. Describes how Hubble's law expansion will be observed identically for all viewpoints, but Hubble's law discussion is problematic or incomplete.
v = 8/20:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Discussion based on evidence of the earlier stages in the history of the universe, with little or no substantive discussion of Hubble's law.
x = 4/20:
Implementation/application of ideas, but credit given for effort rather than merit.
y = 2/20: Irrelevant discussion/effectively blank.
y = 2/20:
Irrelevant discussion/effectively blank.
z = 0/20:
Blank.

Grading distribution:
Section 70160
p: 11 students
r: 10 students
t: 11 students
v: 5 students
x: 3 students
y: 1 student
z: 0 students

A sample "r" response (from student 2421):

20101129

Astronomy midterm question: monolithic collapse model

Astronomy 210 Midterm 2, Fall Semester 2010
Cuesta College, San Luis Obispo, CA

[20 points.] Discuss the evidence for the monolithic collapse model of the Milky Way (spherical gas cloud flattening into a disk). Support your answer using the orbit and metal content properties of halo stars versus disk stars.

Solution and grading rubric:

p = 20/20:
Correct. Discusses evidence supporting the flattening of the Milky Way's shape by explaining how metal content increases for younger generations of stars, and observations that disk stars are metal-rich compared to the metal-poor halo stars above and below the disk.
r = 16/20:
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors.
t = 12/20:
Contains right ideas, but discussion is unclear/incomplete or contains major errors.
v = 8/20:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. At least some discussion related to the monolothic collapse model.
x = 4/20:
Implementation/application of ideas, but credit given for effort rather than merit. Discussion unrelated to the monolithic collapse model.
y = 2/20: Irrelevant discussion/effectively blank.
y = 2/20:
Irrelevant discussion/effectively blank.
z = 0/20:
Blank.

Grading distribution:
Section 70160
p: 17 students
r: 8 students
t: 4 students
v: 6 students
x: 3 students
y: 3 students
z: 0 students

A sample "p" response (from student 1991):

20101128

Astronomy midterm question: same size supergiant and giant stars

Astronomy 210 Midterm 2, fall semester 2010
Cuesta College, San Luis Obispo, CA

Discuss whether or not a supergiant and a giant star with the same size could have the same temperature, and why. Support your answer using the Stefan-Boltzmann law and/or an H-R diagram.

Solution and grading rubric:

p:
Correct. Uses either the H-R diagram and/or the Stefan-Boltzmann law to show that since all supergiants are more luminous than giants, then it is not possible for a supergiant and a giant to have the same size and same temperature (as that would result in the same luminosity).
r:
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors.
t:
Contains right ideas, but discussion is unclear/incomplete or contains major errors. Attempts to use H-R diagram and/or Stefan-Boltzman law with stars of same size and same temperature, while realizing that supergiants and giants have different luminosities, but does not adequately resolve that these two arguments are inconsistent with each other (or resolves this with a plausible overlapping range of sizes/temperatures).
v:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. At least attempts to use H-R diagram and/or Stefan-Boltzman law.
x:
Implementation/application of ideas, but credit given for effort rather than merit.
y:
Irrelevant discussion/effectively blank.
z:
Blank.

Grading distribution:
Section 70160
p: 21 students
r: 7 students
t: 6 students
v: 7 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 1204):

Another sample "p" response (from student 0002):

20101127

Physics midterm problem: total magnetic field of two current-carrying wires

Physics 205B Midterm 2, Fall Semester 2010
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 19.61

[20 points.] Two long straight wires carry different amounts of current in the plane of this page. Determine the direction and magnitude of the magnetic field at the location indicated. Show your work and explain your reasoning.

Solution and grading rubric:

p = 20/20:
Correct. Determines directions of the magnetic fields of each current separately at point P, where B_1 points into the page, and B_2 points out of the page. Finds the magnitudes of these magnetic fields, and since B_2 has a greater magnitude than B_1, the resulting total magnetic field at point P will point out of the page, with a (positive definite) magnitude that is the arithmetic difference of the two magnitudes.
r = 16/20:
Nearly correct, but includes minor math errors. Direction or magnitude of total magnetic field has minor error.
t = 12/20:
Nearly correct, but approach has conceptual errors, and/or major/compounded math errors. Both direction and magnitude of total magnetic field have minor errors.
v = 8/20:
Implementation of right ideas, but in an inconsistent, incomplete, or unorganized manner.
x = 4/20:
Implementation of ideas, but credit given for effort rather than merit.
y = 2/20:
Irrelevant discussion/effectively blank.
z = 0/20:
Blank.

Grading distribution:
Section 70856
p: 8 students
r: 1 student
t: 2 students
v: 0 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 8110):

20101126

Physics midterm problem: light bulb power dissipation in circuit

Physics 205B Midterm 2, fall semester 2010
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 18.63

An ideal 16.0 V emf source is connected to ideal light bulbs and an ideal resistor, as shown at right. Find the amounts of power used by each light bulb. Show your work and explain your reasoning using Kirchhoff's rules, Ohm's law, and electric power.

Solution and grading rubric:

p:
Correct. Determines power of 8.0 Ω light bulb by direct application of P = (∆V)²/R, or first solves for I through light bulb, and then uses P = I·∆V or I²·R. For the 5.0 Ω light bulb, must first solve for the current passing through the lower loop, then uses power = I²·R, or uses voltage drop across the 5.0 Ω light bulb to use P = I·∆V or (∆V)²/R.
r:
Nearly correct, but includes minor math errors. Typically solves correctly for the power used by the 8.0 Ω light bulb, but has conceptual errors in applying Kirchhoff's rules and Ohm's law to determine current passing through and/or voltage drop across the 5.0 Ω light bulb.
t:
Nearly correct, but approach has conceptual errors, and/or major/compounded math errors.
v:
Implementation of right ideas, but in an inconsistent, incomplete, or unorganized manner.
x:
Implementation of ideas, but credit given for effort rather than merit.
y:
Irrelevant discussion/effectively blank.
z:
Blank.

Grading distribution:
Section 70856
p: 7 students
r: 4 students
t: 0 students
v: 0 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 1025). Note that the numerical results here are correct, but there are several errors in setting up calculations:

the equivalent resistance is set up incorrectly--it should be written R_eq = ((5.0 Ω + 4.0 Ω)^–1 + (8.0 Ω)^–1)^–1, but the resulting value is correct.
the power dissipated by the 5.0 Ω light bulb is set up incorrectly--it should be written P = I²⋅R = (1.778 A)²·(5.0 Ω), but the resulting value is correct.

A sample "r" response (from student 1010):

20101125

Found physics: turkey cooling

"...Imagine what would happen if you took a Thanksgiving turkey piping hot from the oven and immediately placed it in a freezer. (Consider a perfect freezer--one that can remove heat instantly and always stay at its set temperature.) Initially the turkey would be at the same temperature throughout (assuming that you had roasted it for sufficiently long). Only a very thin skin would immediately take on the temperature of the freezer. But soon, the outer layers of turkey meat would cool as heat diffused outward, even though the center retained its initial oven-like temperature. Eventually, of course, everything including the stuffing would cool off; that is, the temperature inside your turkey would depend both on the distance from the surface and on the time elapsed since you placed it in the freezer."
--Philip C. England, Peter Molnar, and Frank M. Richter, "Kelvin, Perry and the Age of the Earth," American Scientist, volume 95 number 4, p. 342 (2007)

The "Turkey/Cornish Hen Effect".

Related posts:

Bergman's Rule (wikipedia.org).

Allen's Rule (wikipedia.org).

Physics midterm question: unequal resistors in parallel

Physics 205B Midterm 2, fall semester 2010
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 18.40(b)

An ideal emf source is connected in parallel to two resistors, where r < R. Determine which resistor has more current flowing through it, or if there is a tie. Explain your reasoning using the properties of currents and potential differences, and Kirchhoff's rules and Ohm's law.

Solution and grading rubric:

p:
Correct. Uses Ohm's law and the fact that each resistor has the same voltage drop (from inspection, or from explicit application of Kirchhoff's loop rule) to find that the resistor with the smaller resistance will have the greater current passing through it.
r:
As (p), but argument indirectly, weakly, or only by definition supports the statement to be proven, or has minor inconsistencies or loopholes.
t:
Nearly correct, but argument has conceptual errors, or is incomplete.
v:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner.
x:
Implementation/application of ideas, but credit given for effort rather than merit.
y:
Irrelevant discussion/effectively blank.
z:
Blank.

Grading distribution:
Section 70856
p: 11 students
r: 0 students
t: 0 students
v: 0 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 7175):

20101124

Physics midterm question: changes in potential

Physics 205B Midterm 2, Fall Semester 2010
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Conceptual Questions 17.1, 17.4, 17.6

[10 points.] A positive source charge is held at the origin, and a negative test charge is at x = +4.0 cm. As the negative test charge is moved from x = +4.0 cm to x = +5.0 cm, determine whether it moves to a region of lower or higher potential. Explain your reasoning using the properties of electric potential.

Solution and grading rubric:

p = 10/10:
Correct. The source charge is the sole relevant potential, increasing r in V = k(+Q)/r will decrease the positive numerical value of the potential.
r = 8/10:
As (p), but argument indirectly, weakly, or only by definition supports the statement to be proven, or has minor inconsistencies or loopholes.
t = 6/10:
Nearly correct, but argument has conceptual errors, or is incomplete. Confounds potential of source charge with potential energy of two charges, but at least discussion of how potential energy changes is correct.
v = 4/10:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner.
x = 2/10:
Implementation/application of ideas, but credit given for effort rather than merit.
y = 1/10:
Irrelevant discussion/effectively blank.
z = 0/10:
Blank.

Grading distribution:
Section 70856
p: 3 students
r: 0 students
t: 4 students
v: 4 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 7111):

20101123

Astronomy current events question: Milky Way bubbles

Astronomy 210L, Fall 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, "Why is the Milky Way Blowing Bubbles?," November 11, 2010
http://www.skyandtelescope.com/community/skyblog/newsblog/107302599.html

Images of __________ above and below the Milky Way have been extracted from NASA Fermi Large Area Telescope data.
(A) dark matter.
(B) antimatter vortexes.
(C) disrupted dwarf galaxies.
(D) rogue black holes.
(E) gamma-ray bubbles.

Correct answer: (E)

Student responses
Sections 70178, 70186, 70200
(A) : 6 students
(B) : 1 student
(C) : 8 students
(D) : 2 students
(E) : 46 students

Astronomy current events question: gas-powered comet jets

Astronomy.com editors, "Primordial Dry Ice Fuels Comet Jets," November 11, 2010
http://astronomy.com/en/News-Observing/News/2010/11/Cometary%20dry%20ice%20jet%20fuel.aspx

The NASA EPOXI spacecraft observed jets of gas and particles powered by __________ bursting from Comet 103P/Hartley 2.
(A) oxygen.
(B) water vapor.
(C) nitrogen.
(D) carbon dioxide.
(E) methane.

Correct answer: (D)

Student responses
Sections 70178, 70186, 70200
(A) : 0 students
(B) : 9 students
(C) : 10 students
(D) : 43 students
(E) : 2 students

Astronomy current events question: Eris vs. Pluto

Kelly Beatty, "Eris Gets Dwarfed (Is Pluto Bigger?)," November 7, 2010
http://www.skyandtelescope.com/news/106861063.html

Astronomers in Chile recently observed dwarf planet Eris __________, which may indicate that it is slightly smaller than dwarf planet Pluto.
(A) passing in front of a star.
(B) during a continent-wide power outage.
(C) eclipsed by Pluto.
(D) using infrared and radio waves.
(E) bombarded by an impactor.

Correct answer: (A)

Student responses
Sections 70178, 70186, 70200
(A) : 51 students
(B) : 2 students
(C) : 8 students
(D) : 2 students
(E) : 1 student

20101122

Education research: introductory astronomy midterm statistics

Cuesta College Astronomy 210 (introductory astronomy lecture) students take their second midterm on spectra, stars, galaxies and cosmology in the fourteenth/fifteenth week of instruction.

The midterm consists of ten multiple-choice questions (with partial credit for multiple-choice), and three short-answer questions (graded with a standardized rubric), to be completed within 80 minutes (the length of a regularly-scheduled lecture).

Grading statistics:

Cuesta College
Astronomy 210 Fall Semester 2010 section 70158
Midterm 2 results (N = 46, max score = 100):
   0- 20.0 :   
20.5- 40.0 : ***  [low = 23.5]
40.5- 60.0 : ************
60.5- 80.0 : ***************  [mean = 69.2 +/- 20.2]
80.5-100.0 : ****************  [high = 100.0]

The order in which students turned in their completed midterms was recorded, beginning approximately 10 minutes after starting, to 70 minutes after starting. With a linear regression r^2 value of 0.0395, there is no significant correlation between the time spent working on the midterm and resulting score (y = 0.299x + 62.181).

Grading statistics:

Cuesta College
Astronomy 210 Fall Semester 2010 section 70160
Midterm 2 results (N = 41*, max score = 100):
    0- 20.0 :   
20.5- 40.0 : *****  [low = 28.5]
40.5- 60.0 : ********
60.5- 80.0 : ******************  [mean = 66.8 +/- 19.3]
80.5-100.0 : **********  [high = 96.5]

*Two students were excluded from the linear regression, due to taking the midterms outside of the normal time allotted for the rest of the class (and thus were not ordered). With a linear regression r^2 value of 0.0796, there is no significant correlation between the time spent working on the midterm and resulting score (y = 0.473x + 56.271).

20101121

Physics quiz question: loop pulled parallel to wire

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

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Multiple-Choice Question 19.4; Problem 20.15.

Consider a long straight wire with constant current. In the plane of the page, a square metal loop (of resistance R) moves parallel to the wire, opposite the direction of current in the wire. While the loop is moving, the direction of current induced in the loop is:
(A) clockwise.
(B) counterclockwise.
(C) (No direction, as there is no induced current.)
(D) (Not enough information is given.)

Correct answer: (C)

The magnetic field of the wire creates a magnetic flux that points out through the square loop. Since the square loop is pulled parallel to the wire, the amount of flux through the square loop does not change over time, such that from Faraday's law:

emf = -N*(delta(phi_B)/delta(t));

since the magnetic flux phi_B is is constant, then there is no induced emf in the square loop, and thus no current induced in the square loop.

Student responses
Section 70856
(A) : 4 students
(B) : 6 students
(C) : 1 student
(D) : 0 students

Success level: 9%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.17

20101120

Physics quiz question: self-inductance

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

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 20.55.

The current passing through an ideal inductor L is increasing over time. The __________ end of the inductor is at a higher potential.
(A) left.
(B) right.
(C) (There is a tie.)
(D) (Not enough information is given.)

Correct answer: (B)

From Lenz's law, the inductor will have a back emf induced in it that will fight the increasing current flowing to the left, resulting in the right end being at a higher potential (with the left end at a lower potential), corresponding to an induced current that points to the right, opposite the direction of the increasing external current.

Student responses
Section 70856
(A) : 5 students
(B) : 6 students
(C) : 0 students
(D) : 0 students

Success level: 54%
Discrimination index (Aubrecht & Aubrecht, 1983): 1.00

20101119

Physics quiz question: motional emf

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

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 20.1

A conducting rod 0.50 m in length moves at a constant speed through a uniform magnetic field. A longer rod 1.0 m in length moving with the same speed in the same direction in this magnetic field would have a potential difference __________ the 0.50 m long rod.
(A) less than.
(B) the same as.
(C) more than.
(D) (Not enough information is given.)

Correct answer: (C)

The motional emf in a rod of length L, moving through a perpendicular, uniform magnetic field B is given by:

emf = v*B*L.

So a longer rod would experience a proportionally greater motional emf.

Student responses
Section 70856
(A) : 0 students
(B) : 2 students
(C) : 9 students
(D) : 0 students

Success level: 81%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.08

20101118

Cuesta College North County campus star party

20101118775
http://www.flickr.com/photos/waiferx/5188395513/
Originally uploaded by Waifer X

Waxing gibbous moon, November 18, 2010, photographed with a hand-held Nokia e71 smartphone through an Orion SkyQuest XT8 8" reflector at Cuesta College North County Campus, Paso Robles, CA.

Sights seen:
Waxing gibbous moon
Jupiter, north equatorial belt, four Galilean satellites

20101117

Online reading assignment question: big bang tags (post-instruction)

Astronomy 210 Reading Assignment 13, Fall Semester 2010
Cuesta College, San Luis Obispo, CA

101117-postbigbangwordle
http://www.flickr.com/photos/waiferx/5185879732/
Originally uploaded by Waifer X

Wordle.net tag cloud for "big bang" (post-instruction) generated by responses from Astronomy 210 students at Cuesta College, San Luis Obispo, CA (http://www.wordle.net/show/wrdl/2749023/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 "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 70158, 70160

boom, hot, fast, confusing, isawithappen
huge, new, theory, interesting, stars
beginning, dust, starclusters, galaxies
bigbang, expansion, birthofuniverse, confusing, epic
redshifts antimatter matter CMB nucleosynthesis
finitespeedoflight Hubbletime bigbang CMB noceilings
rapidexpansion redshifts particleaccelerators GeorgeLemaitre
theory
expansion, antimatter, annihilation, nucleosynthesis, reionization
universe start boom show theory
wowzers poof universe life stardust
space, elements, newelements, populationI, populationII
theory TVshow explosion planets God theory religion
explosion, formation, Earth, space, blast
beginning, hot, quick, expansion, awesome
stars, gravity, planets, hydrogen, lightwall
expansion, galaxies, CMB, Hubbletime, antimatter
nobang, backintime, TVshow
lookbacktime, finite, composition, nothing, purehydrogen
annihilation hydrogen reionization nucleosynthesis atoms
expansion, beginning, hot, dense, 14bya
theory, universe, formation, Olbersquestion, Hubbleslaw
beginning CMB expansion deuterium
hot, dense, rapid, expansion, 14bya, hypothesis
matter, mass, energy, rapid, expansion, antimatter
bigbang, Hubbletime, CMB, antimatter, boom
birth, universe
hypothesis, hardtoargueagainst, formationofeverything, hydrogen
expansion, Hubbleslaw, beginning, CMB, lookbacktime
expansion, universe, galaxies, starformation, hot dense
expansion hot dense CMB matter antimatter
beginning, universe, lookbacktime, reionization, stars
bigbang, crazy, dust, space, sweet!
bigbang stars blastoff
starsform, nucleosynthesis, planets, sun, Earth, moon
expansion, gas, dust, infinite, light
beginning spacetime
beginning universe
matter antimatter space gravity energy
explosion, theory, universe, expansion, years
theory, expansion, time, heat, lookbacktime
finite, redshifts, velocity, CMB, expansion
beginning start infinite energy universe
supernova galaxy solarsystem stars
ThomasErak, explosion, theory, TVshow, truth
huge loud dark manystars
expansion, explosion, redshifts, timecurve, lookbacktime
expansion, CMB, lithium, hydrogen, CalvinandHobbes
big, bang, theory, light, expansion
bigbang freakingawesome
nobang expansion theory 14bya matter
time, space, distant, light, spreading
loud, bright, big, bang, me
beginning, 14bya, CMB, fusionsoup, TVshow
1929thebigcrash explosion physics stringtheory evolution
warm, dense, kaboom, universe, matter
bomb, rocksflyinginspace
start, life, mass, TVshow, space
loud, prettycolors, chemicalsreacting, incomprehensible, space
delicious, ultimate, tasty, bigbang
boom, beginning, expansion, belief, power

Online reading assignment question: big bang tags (pre-instruction)
(Fall semester 2009).
Online reading assignment question: big bang tags (pre-instruction)
(Spring semester 2010).
Online reading assignment question: big bang tags (pre-instruction)
(Fall semester 2010).

Astronomy current events question: Kuiper belt object colors

Astronomy.com editors, "Kuiper Belt of Many Colors," November 1, 2010
http://astronomy.com/News-Observing/News/2010/11/Kuiper%20Belt%20of%20many%20colors.aspx

Scientists from NASA's Goddard Space Flight Center have proposed that the many different colors of Kuiper belt objects may come from:
(A) different layers exposed by the sun.
(B) tidal heating.
(C) sulfur-rich volcanoes and geysers.
(D) radioactive decays.
(E) simple organisms similar to algae or lichen.

Correct answer: (A)

Student responses
Sections 70178, 70186, 70200
(A) : 32 students
(B) : 3 students
(C) : 1 student
(D) : 3 students
(E) : 5 students

Astronomy current events question: EPOXI spacecraft previous mission

Astronomy.com editors, "Deep Impact Flyby Spacecraft Images Comet 103P/Hartley," November 4, 2010
http://astronomy.com/en/News-Observing/News/2010/11/Deep%20Impact%20Flyby%20spacecraft%20images%20Comet%20103P%20Hartley.aspx

Before flying past Comet 103P/Hartley 2, the NASA EPOXI spacecraft was originally called the Deep Impact spacecraft, which had successfully completed its mission of:
(A) returning samples from a dark nebula.
(B) shooting a projectile into the nucleus of another comet.
(C) flying through the asteroid belt.
(D) surveying the moon's surface for traces of water.
(E) tracking and deflecting a potential asteroid impactor.

Correct answer: (B)

Student responses
Sections 70178, 70186, 70200
(A) : 1 student
(B) : 31 students
(C) : 4 students
(D) : 3 students
(E) : 5 students

Astronomy current events question: Saturn ring debris mountains

Annalee Newitz, "Two-Mile-High Mountains Discovered in Saturn's Rings," November 1, 2010
http://io9.com/5678790/two+mile+high-mountains-discovered-in-saturns-rings?skyline=true&s=i

The NASA Cassini spacecraft has recently imaged __________ in Saturn's rings, which may be caused by gravitational fluctuations between Saturn and its moons.
(A) snow cyclones.
(B) debris mountains.
(C) spiral arms.
(D) moonlet formation.
(E) liquid nitrogen geysers.

Correct answer: (B)

Student responses
Sections 70178, 70186, 70200
(A) : 0 students
(B) : 39 students
(C) : 2 students
(D) : 1 student
(E) : 1 student

20101116

Astronomy quiz question: dark matter locations

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

Dark matter in the Milky Way is located:
(A) between the spiral arms.
(B) above and below the disk, in the halo.
(C) in supergiant cores.
(D) inside the central supermassive black hole.

Correct answer: (B)

In order for all stars to have nearly the same orbital speed at different distances from the center of the Milky Way, mass must be distributed evenly as dark matter above and below the Milky Way disk, out in the halo.

Section 70160
(A) : 15 students
(B) : 19 students
(C) : 0 students
(D) : 3 students

"Success level": 55% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.39

20101115

Astronomy quiz question: the sun's Milky Way location

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

__________ is evidence that the sun is located near the outer rim of the Milky Way disk.
(A) Most stars in other galaxies are found near their outer rims.
(B) Very few stars in the direction out towards the rim.
(C) How slowly the sun orbits the center of the Milky Way.
(D) Star cluster positions above and below the disk.

Correct answer: (D)

Globular star clusters can be easily seen above and below the disk of the Milky Way, unimpeded by interstellar gas and dust within the disk of the Milky Way, and their locations are centered on the gravitational center of the Milky Way.

Section 70160
(A) : 1 student
(B) : 6 students
(C) : 14 students
(D) : 16 students

"Success level": 48% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.62

20101114

Astronomy quiz question: no center of universe expansion

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

__________ is evidence that the universe has no center of expansion.
(A) Matter and antimatter annihilate to convert into energy.
(B) Galaxy redshifts are proportional to galaxy distances.
(C) The finite speed of light.
(D) The night sky is dark, and not blindingly bright.

Correct answer: (B)

The Hubble law indicates that space is expanding, such that galaxies which are stationary within this expanding space will appear to recede faster from an observer the more distant they are. Since this would be true for any observer at any location in this expanding space universe, such that the expansion would not have a center.

Section 70158
(A) : 1 student
(B) : 38 students
(C) : 5 students
(D) : 1 student

"Success level": 86% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.22

20101113

Astronomy quiz question: halo vs. disk population star age

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

Evidence that halo population stars are older than disk population stars is that halo population stars:
(A) contain dark matter.
(B) are less massive.
(C) have dimmer luminosities.
(D) have fewer absorption lines.

Correct answer: (D)

Each element will produce its own characteristic set of absorption lines. A star that had formed recently will be metal-rich, and have many absorption lines, while a star that had formed a long time ago will be metal-poor, and have fewer absorption lines.

Section 70158
(A) : 2 students
(B) : 8 students
(C) : 12 students
(D) : 22 students

"Success level": 53% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.34

Section 70160
(A) : 4 students
(B) : 4 students
(C) : 6 students
(D) : 23 students

"Success level": 66% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.71

20101112

Astronomy quiz question: globular star clusters

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

The locations of globular star clusters provide evidence for:
(A) the location of the Milky Way's center.
(B) dark matter in the halo.
(C) self-sustaining star formation.
(D) the spiral arm structure of the Milky Way.

Correct answer: (A)

Globular star clusters can be easily seen above and below the disk of the Milky Way, unimpeded by interstellar gas and dust within the disk of the Milky Way, and their locations are centered on the gravitational center of the Milky Way.

Section 70158
(A) : 22 students
(B) : 5 students
(C) : 2 students
(D) : 16 students

"Success level": 54% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.73

20101111

Online reading assignment question: keep, quit, start

Astronomy 210 Keep-Quit-Start Reading Assignment, Fall Semester 2010
Cuesta College, San Luis Obispo, CA

101110-keep
http://www.flickr.com/photos/waiferx/5165510496/
Originally uploaded by Waifer X

Wordle.net tag cloud for "keep" resolutions generated by responses from Astronomy 210 students at Cuesta College, San Luis Obispo, CA (http://www.wordle.net/show/wrdl/2714070/Untitled).

101110-quit
http://www.flickr.com/photos/waiferx/5164907651/
Originally uploaded by Waifer X

Wordle.net tag cloud for "quit" resolutions generated by responses from Astronomy 210 students at Cuesta College, San Luis Obispo, CA (http://www.wordle.net/show/wrdl/2710267/Untitled).

101110-start
http://www.flickr.com/photos/waiferx/5165510444/
Originally uploaded by Waifer X

Wordle.net tag cloud for "start" resolutions generated by responses from Astronomy 210 students at Cuesta College, San Luis Obispo, CA (http://www.wordle.net/show/wrdl/2710322/Untitled).

Students were asked to answer a "keep-quit-start" online reflection (hosted by SurveyMonkey.com) on their studying strategies/pitfalls (Mubayiwa, 2009).

Enter a word or brief phrase that describes what you intend to keep doing to study for this class. Explain your answer to the above question (what you intend to keep doing to study for this class).

Enter a word or brief phrase that describes what you intend to quit doing to study for this class. Explain your answer to the above question (what you intend to quit doing to study for this class).

Enter a word or brief phrase that describes what you intend to start doing to study for this class. Explain your answer to the above question (what you intend to start doing to study for this class).

[Word tags have been edited to consolidate related common subjects; student explanations are verbatim.]

Student responses
Sections 70158, 70160

Keep word tags:

ask
for help from smart science people.

cram
I remember things better if i focus on studying right before the test.

flashcardquestions ("peer instruction," "think-pair-share")
Review the flashcard questions that have to do with the quiz and review notes and keep up with reading.
I plan on keep reviewing the flash card questions online.
At first I didnot do the falsh card questions and now I have been doing them and my last quis I got a 36. so it was a big jump form 22.
I want to keep studying the flashcard questions and quiz questions to better prepare me.
Complete all flashcard questions and check over answers from the text
By printing the flashcard questions and bringing them to class to get answers to some of them helps me to study for the quizes and midterms

gotoclass
Keep up with the normal homework online/ extra credit: it helps a lot with remembering things over the week break. Going to class keeps my participation points and understanding up.
I feel like coming to class is the best way to learn for this particular course. Since I don't really understand any of this material on my own, I need to help from the ever-wise P-Dog to learn it.
I learn the most during lecture and in-class activities. I don't study very effectively from the book.
just need to keep going to class that way i get the main points out if you and then follow it up with the bok and studying
Coming to class gives you everything you need to know. As long as you pay attention to lectures and do in class activities, the rest should come pretty easy.

groupstudy
Having my friends explain things to me helps.
Its always better to have two brains than one.

inclassactivities ("lecture-tutorials")
I think that the powerpoints are really good at giving us the tools we need to do the work, and the inclass assignments are what help us to apply those tools.
it helps refresh my mind. I look back on my notes more and remeber the leture.

library
I will keep going to the library to study for the class

listen
it really helps
listen, notes
i remember things easily if i wrote down what the teacher was saying.

maketime
cuz im so busy with two jobs i have to maintain a good schedule an sleep pattern an make alot of time to study

notes
Because it helps me get most of the questions right.
When I take notes in class it helps me to listen to what is being taught and write it down.
I intend to keep studying notes that we take in lecture and during flashcard questions, because most of those concepts are on the quizzes.
I always look at my notes before the test, and try to compare them to the book. So I am going to continue to take notes in class.
I try to take in depth notes on the things gone over in class and try to make the flash card questions into notes as well
i take good notes:)
Its important to take good notes during the lecture, and also for the book. It helps a lot when it comes to quiz/exam time!
taking thourough notes in class really helps with my studying.
notes, flashcardquestions
The notes that I take in class, and the flashcard questions that we go over in class have been helpful for me in studying for this class.

notes, inclassactivities
It helps you remember what actually happened in the lecture because sometime notes aren't good enough and you need the power points

onlinereadingassignments ("reading quizzes")
What I mean by this is keeping up with the work. Completing the online assignments and in-class activities.

onlinereadingassignments, gotoclass
being in class is key and reading the book is interesrting and provides everything i need to know

payattention
The book really hasnt been necessary for me in this class so far because the assignments and lectures have been able to carry me through pretty well.

practiceexams
This has helped me a lot for studying for all the quizes and tests.
When I study I look at the previous quizzes from older semesters. This gives me a good idea of what to expect on the quiz
I think that going over the quizes and flash card questions really help me to grasp the material and types of questions that will be on the test and thus help me to study so that I can retain the knowledge and score well on quizes.
I think it is pretty self explanatory.
i like to study and practice the practice tests
Looking at quizzes from past years helps me study for each quiz because they give me the best idea as to what things I have to know to do well on the quizzes.
The old quizzes cover a lot of questions that are or are similar to those on the actual quiz. I generally get most of my answers right because of the old quizzes.
Look at older quizes and tests to help me get a feel for what I need to go over.
I'm going to keep taking the previous quizzes that are posted online and looking up the answers that I don't know.
Keep going over old quiz's. I just wish the answer key for them could be online.
They provide a good clue as to what I should be studying.
Keeping the the quizes to study really helps when it comes time to take the midterms
I'll keep the old quizzes he turns back in because they have a lot of similar questions as on the test.
I have found it useful to study my own old quizzes as well as the quizzes posted online from other classes.

practiceexams, flashcardquestions
By using older versions of quizes coupled with the flashcard questions I can more effectively extract pertinent information from the book, lecture notes, and in class activities.

practiceexams, inclassactivities
it is really important to review these things because the activities we work in groups and it helps me understand things better and the quizzes help because it is a fast review of a lot of things that we should have learned

read
open the book and try to comprehend what i am reading
i need to read the book more to understand the chapter
I plan on keeping on reading my textbook for studying because it contains information that I can process and retain. This really helps me study
well ive been reading the book so i'd figure i should keep doing that.
Read the chapters
I intend to keepp reading from the textbook
If I read ahead, I'll know what to expect in class/will already have an idea of the material.
reading helps me understand something better than just listening to it.
read the textbook

read, flashcardquestions
reading covers most of what we talk about in class, and the flashcards are very knowledgeable and help because they are similar to test questions.

read, listen
I intend to read my notes and book and pay attention in class, also i plan to read the flash card questions

review
Review flash card questions and old tests posted online.
I review a lot of my notes. I go over all the flashcard questions that were asked and their answers.

start
I need to begin to study more seriously for this class. I have not done that very much

truckin'
I Gotta Keep On Truckin' haha

Quit word tags:

?
Maybe study a little and not play so much Halo Reach

cooking
cutting up fresh tomatoes, chopping onions and slicing avocados takes way too much time

cram
Study at least 4 days in advance before the quiz

distractions
Astronomy is killing my K/D
well it's hard to care about a class when you read the chapters, go to class, and study with a good partner and still do poorly...
cuz i always intend to study an do hwk but i always end up playing video games
Pretty self explanatory but in order to study I'll have to cut back on the time I spend with my friends.
It's distracting!
i watch tv while studying.
Distractions = poor grades.

don'tknow
There's nothing that I really need to quit doing,

Facebook
it distracts me from everything.
its to addicting!
i need to quit distracting myself

flashcardquestions
Although the flash card questions are very helpful, they are very time consuming and I have other work that I have to do aswell. The powerpoints and inclass activities are really all I need to go over.

forgettingonlinereadingassignments ("reading quizzes")Sometimes I make a habit of forgetting to write down homework, therefore I don't do it.
I sometimes tend to forget to do them. So I should stop that.

goofingoff
Sometimes when I am reading my mind wanders about pointless things and I stop reading for awhile until I can get my mind back on track.

lecture
I need to quit expecting lectures to teach me what I need to know because there's a lot we don't cover in class

memorizationonly
When I rely on my memory to answer quetstions on the tests and quizzes, I don't do very well.

nonotes
i need to take better notes

notaskingquestions
I find when i finally just ask the question i wanted to, its not always as dumb of a question as i thought it would be
i need to stop not asking questions and start asking more so that i can get a better understanding of everything that we have learned for the day

nothing
I have been doing everything I need to do. I just need to do it.
i don't do anything unnecessary when studying
Nothing. I'm doing good
I don't intend to quit anything, because no study habit at the moment is inhibiting quiz grades.
i don't intend to quit doing anything...
i want to do more than i have been and finish off the semester strong, not quit doing anything
i feel that everything i do benefits me in some way.
If anything I need to spend more time doing the things I am already doing
I'm not going to quit anything.
I'm satisfied with my performance in the class so far so I need to maintain rather than quit.

notlistening
I have realized that flashcard questions are actually very important and usually show up again on quizzes and tests.

notreading
At first I was only reading the book, now I know that I also need to use the flashcard questions and In class activities to study for this class.
I need to go through the book a lot more when I study and read through everything thoroughly so I better understand the material.
i dont read all the chapter let alone all of it so i miss out on alot
I find that I only read parts of the chapters, and not the entire chapter. So I need to make sure I am not only reading parts of the chapters.
I need to use the book a bit more probably
i only do a quick read of the book
Sometimes I don't always read the chapters in the book and I need to spend more time doing that.

notreviewing
The online flashcard questions are almost exactly the same as quiz questions.

notstudying
studying half way only helps you with part of the test
Studying is essential for this class!

procrastination
I need to stop procrastinating when it comes to studying for a test.
I need to stop waiting until the last minute to study!
Have to stop neglecting questions that don't make sense and ask for help.
I usually end up studying on the day of the quiz which is not a good formula for success.
I WOULD WIN A MILLION AWARDS FOR IT:)
quit putting off studying till the last second
study, yo!
It's fairly self explanatory
Cramming information in a couple of hours is usually lost right after the test.
I'm going to stop waiting so long to study and start doing that earlier.
If i quit waiting until the last minute to study then maybe I would have time to email P dawg my answers to the practice quiz's.
Waiting for the last minute to do things such as study for a quiz or do the online reading assignments does not help at all
procrasinating in any class is not a good idea
quit procrastinating on the reading
cramming for me, i find, only works for English classes for some reason.
I intend to study for tests and quizes a week before they are given.
I need to sometimes stop putting things off and just do it.
I need to quit being lazy, start studying and taking this course more seriously

reading
Reviewing or re-reading the book only makes me more confused when I'm trying to study for a quiz. There is too much information to remember, and a lot of it isn't on the quiz anyway.

stayuplate
I have been staying up late studying and I am not getting the grades I want, maybe if I get more sleep and a better rest I will do better.

WorldofWarcraft
it is a big time waster. and distracts from study time.

Start word tags:

ask
it really helps!
Its always nicer to have something explained by the teacher, or even other students rather than researching it later when you have to go digging for the answer.
Asking for help when I don't understand
sometimes its scary to ask questions but at times its what really helps.

becool
just trying to be like p-dog

extracredit
I intend to start doing outreach activities for bonus points, to get as many as possible because I'd like an A in the class.

flashcardquestions ("peer instruction," "think-pair-share")
There are a few flashcard questions on quizzes that surprise me because I've never seen them before in my life. That's probably not a good thing...
The flash card questions help me understand topics like star luminosity or ones that don't have answers that we can memorize. They help me learn to figure out answers for these kind of questions easier.
I think looking at both the older quizes and the flash card questions will help give me even more practice.
Looking over more flashcard questions.
every single question that gets posted make sure you get the answer too.
Starting writing down the flash card questions and answers
the flashcards are the most helpful part

focus
i need to focus more on taking more time to study and get a good grip on things so that when i get home i understand things

getfeedback
I need to send my flashcard Q answers to Mr Len ahead of time

groupstudy
Start participating in more group studying.

practiceexams
i need to study more for midterm one and ace the last couple tests
If I email my teacher my answers to previous quizzes he will give me the correct answers or give me a better explanation to help me figure the answer out. now i will know what i am answering wrong and right
I have yet to study old tests so I can obtain information that I have lost or stored somewhere in my memory that prepares me for the final and midterm tests.
Practice is a good idea.

practiceexams, flashcardquestions
Utilizing old quiz versions and flashcard questions as study guides has helped me so I need to start thinking about looking at the relevant material for the next exam.

prepare
I feel that if I do this I will be better prepared for the class and understand things more easily.

read
I need to start reading the chapters more in depth. I ususally just skim them I need to really deeply read them.
I feel like those might give me that little bit more info that helps everything sink in after going over it.
i haven't been reading the book before quizzes.
If I read all of the chapters that we study, i should be able to also look at the notes and hopefully be able to raise my grade in the class.
More in depth reading of the book. I think that I'm reading it too quickly and not fully understanding the material.
I intend to read the book more!!
reading the book
I want to read all the sections that we will cover in class, and that will be on the tests and quizzes. I really want to get a better grade on my quizzes.
read the book more in depth
I do look at the book, but there are certain sets of pages that actually help quite a bit for the quizzes.
I want to start reading the chapter in the book before we go over it in class because I think it will help me better understand the topics
I don't usually read the full chapters, I just read the parts I find the most needed for the reading assignments and the quizzes.
I have found that the summary at the end of each chapter is very useful and I intend to start doing that every week.
Same as number one
i intend to read the book and the chapters
I plan to read the chapters more carefully and ask questions for things I don't understand.

review
go over more of the previous quizzes to help prepare for the next quiz
I missed a question because of a small detail that i didn't pick up in class, but i probably had it in my notes if i had looked close enough.
I'm going to go over the chapters in the book more than once.
i'm going to review my notes more often and before quizzes.

Ritalin
I intend to start taking Ritalin haha

start
I basically need to start doing it.

startsooner
Starting a little earlier cant hurt
I need to give myself time to take in all the information so I can learn it better
I would like to study a good three days before the test to be EXTRA prepared!!!
Study more and study sooner!!
I leave studying to the very last minute.

studygroup
Studying with a couple friends in the class
Studying in a group will not only insure that I do well on quizzes and tests, but that other people will too.
It helps to have someone to explain the material too and have explained to you if you're unsure.

studymore
I need to start studying earlier than the week of a test or quiz. I want to start studying a week before.
With my busy schedule I don't think that I spend enough time studying so I am going to plan more time into my schedule for studying for this class.
i need to study much more than i do i really dont study all that much so i need to start looking back at the old quizzes
cuz i dont study hard enough to get the grades i set for my self
I have never really had a class where I can take advantage of online work, so I am going to use the online work given.
sometimes the quiz questions aren't basic information questions, you need to have a full understanding to answer the question correctly
Before quizzes, I need to start studying more. That'll help alot.

studymore, prepare
Print out all flash cards and old quizzes and study the answers to those questions.

takenotes
I definitely slacked on notes early in the semester for this class, so I need to start taking much better ones from now on.
i need to take notes as i read so that i can look back on the key points.

timemanagement
By that i mean, i'll leave more time to study for this class than doing other classes' homework.

try
harder than i do now.

understandinclass
Asking a neighbor any questions so everything is clear in my head before I study at home.

Resources:
Bruce Tendai Mubayiwa, "KQS!", http://journeysinlife.com/2009/10/kqs/.

Acknowledgement to Peter Newbury (@polarisdotca), University of British Columbia, for the keep-quit-start inspiration:
http://twitter.com/#!/polarisdotca/status/28917849482.

20101110

Physics quiz question: circuit breaker

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

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 18.97

The circuit breaker for a power outlet strip that supplies 120 V is rated for 7.0 A. Suppose a laptop computer draws 24 W, a lamp draws 300 W, and a popcorn popper draws 600 W. Which will draw the most current without tripping the breaker?
(A) Laptop and lamp.
(B) Popcorn popper.
(C) Laptop and popcorn popper.
(D) Popcorn popper and lamp.
(E) Laptop, lamp, and popcorn popper.

Correct answer: (C)

The maximum power output for the strip outlet, without tripping the breaker, is:

Power = I*delta(V) = (7.0 amps)*(120 volts) = 840 watts.

Running these appliances, respectively, uses these amounts of power:
(A) 24 watts + 300 watts = 324 watts.
(B) 600 watts.
(C) 24 watts + 600 watts = 624 watts.
(D) 600 watts + 300 watts = 900 watts.
(E) 24 watts + 300 watts + 600 watts = 924 watts.

Thus running the laptop and popcorn popper will draw the most current (I = Power/delta(V) = (624 watts)/(120 volts) = 5.2 amps) without tripping the breaker. Running the popcorn popper and lamp, the next higher power combination of appliances, would result in a current I = Power/delta(V) = (900 watts)/(120 volts) = 7.5 amps, which would trip the circuit breaker. Running all three appliances would result in a current I = Power/delta(V) = (924 watts)/(120 volts) = 7.7 amps, which would also trip the circuit breaker.

Student responses
Section 70856
(A) : 0 students
(B) : 2 students
(C) : 4 students
(D) : 1 student
(E) : 4 students

Success level: 36%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.83

20101109

Physics quiz question: discharging capacitor

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

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

Consider a 20 µF capacitor connected to an 8.0 kV potential difference such that it is fully charged. The capacitor is then disconnected from the potential source, and a 200 ohm resistor is connected to the capacitor at t = 0. At what time t will the voltage across the capacitor have 50% of its original value?
(A) 0.0020 s.
(B) 0.0028 s.
(C) 0.11 s.
(D) 0.69 s.

Correct answer: (B)

For a discharging capacitor,

delta(V) = emf*exp(-t/tau),

where the time constant tau = R*C. Solving for t:

delta(V)/emf = exp(-t/tau),

ln(delta(V)/emf) = -t/tau,

t = -tau*ln(delta(V)/emf) = -R*C*ln(delta(V)/emf) = -(200 ohms)*(20e-6 farads)*ln(0.50) = 0.002772588722 s ≈ 0.0028 s.

Response (A) is R*C/2; response (C) is -C*emf*ln(1/2); response (D) is -ln(1/2).

Student responses
Section 70856
(A) : 1 student
(B) : 7 students
(C) : 2 students
(D) : 1 student

Success level: 63%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.83

20101108

Physics quiz question: ammeter in circuit

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

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 18.65

An ideal 12.0 V emf source is connected to ideal resistors and an ideal ammeter, as shown at right. The ammeter reading is:
(A) 1.2 A.
(B) 2.2 A.
(C) 3.4 A.
(D) 8.0 A.

Correct answer: (B)

Writing out the loop rule for the bottom loop, starting from the junction left of the battery:

Summation(delta(V))_loop = 0 = +(12.0 volts) - I*(1.5 ohms) - 0 - I*(4.0 ohms),

where the ideal ammeter does not cause a voltage drop. Solving for the current through the lower loop:

I = +(12.0 volts)/(1.5 ohms + 4.5 ohms) = 2.1818... amps ≈ 2.2 amps.

Response (A) is (12 volts)/(10.0 ohms); response (C) is the current that passes through the battery; response (D) is (12.5 volts)/(1.5 ohms).

Student responses
Section 70856
(A) : 2 students
(B) : 5 students
(C) : 3 students
(D) : 1 student

Success level: 45%
Discrimination index (Aubrecht & Aubrecht, 1983): 1.00

20101107

Astronomy current events question: subsurface water on Mars

Guy Webster & Dwayne Brown, "NASA Trapped Mars Rover Finds Evidence of Subsurface Water," October 23, 2010
http://www.nasa.gov/mission_pages/mer/news/mer20101028.html

NASA's Mars Exploration Rover Spirit detected __________, which may be evidence for subsurface water on Mars.
(A) evaporated puddles.
(B) small and steady Marsquakes.
(C) permafrost.
(D) fossilized quicksand.
(E) different composition soil layers.

Correct answer: (B)

Student responses
Sections 70178, 70186, 70200
(A) : 12 students
(B) : 0 students
(C) : 16 students
(D) : 2 students
(E) : 34 students

Astronomy current events question: spiral galaxies in infrared light

Astronomy.com editors, "Spiral Galaxies Stripped Bare," October 28, 2010
http://astronomy.com/en/News-Observing/News/2010/10/Spiral%20galaxies%20stripped%20bare.aspx

The European Southern Observatory’s (ESO) Very Large Telescope (VLT) HAWK-I camera images spiral galaxies using infrared light, which is:
(A) not affected by spiral arm dust.
(B) not affected by dark matter.
(C) not affected by local light pollution.
(D) arriving at Earth just before the galaxies collided.
(E) slower and steadier than visible light.

Correct answer: (A)

Student responses
Sections 70178, 70186, 70200
(A) : 45 students
(B) : 6 students
(C) : 11 students
(D) : 1 student
(E) : 2 students

Astronomy current events question: Large Binocular Telescope Interferometer

Tom Beal, The Arizona Daily Star, "Graham Scope Has Both Eyes Open," October 23, 2010
http://www.skyandtelescope.com/news/wires?id=151393738&c=y

The Large Binocular Telescope Interferometer uses infrared light combined from two 8.4-meter mirrors in order to detect the presence of:
(A) distant star parallaxes.
(B) Earth-like planets.
(C) previously unseen spiral galaxies.
(D) near-Earth orbit asteroids.
(E) close binary star systems.

Correct answer: (B)

Student responses
Sections 70178, 70186, 70200
(A) : 5 students
(B) : 48 students
(C) : 9 students
(D) : 4 students
(E) : 4 students

20101106

Online reading assignment question: big bang tags (pre-instruction)

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

101117-prebigbangwordle
http://www.flickr.com/photos/waiferx/5185277783/
Originally uploaded by Waifer X

Wordle.net tag cloud for "big bang" (pre-instruction) generated by responses from Astronomy 210 students at Cuesta College, San Luis Obispo, CA (http://www.wordle.net/show/wrdl/2749050/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 "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 70158, 70160

huge, theory, nosound, dense, hot, theory
theory, formation, hot, dense, cooling, expansion
universe, theory, explosion, bang, longtimeago
explosion, expansion, matter, energy, darkmatter
explosion, creation, energy, mass, time
expansion, 14bya, highdensity, hightemperature, galaxies
Bible, theory, explosion, matter, Smurfberries
explosion, controversy, formationoflife, fromnothingtoeveryhting
Hubbletime, explosion, expansion, redshift, cosmicintensity
timezero, galaxies, universe, expansion, kaboom
expansion, galaxies, CMB, dense, hotgas
universe, creation, theory, explosion, stars
universe, created, random, howdidithappen, cool
theory, universe, explosion, atoms, go
bang, universe, gigantic, cold, compacted
bigexplosion, lotsofstars, lotsofgalaxies, lotsofplanets, lotsofgas
energy, expansion, gas, extremeheat, birth
Ihavenoideawhatitis
14bya, highdensity, hightemperature, historicalevent, occurredeverywhere, GeorgesLemaitre
explosion, theory, hot, atoms, universe, galaxies
Hubbletime, cosmic, microwave, background, radiation
big, bang, theory, science, old
TVshow, universe, primevalatom, galaxyclusters, darkmatter
theory, TVshow, Hubbletime, CMB, expansion
angrycreationists, scienceisgod, Ewoks
atoms, explosionstartinglife, universeborn, creationofmatter, creationoftime
escapevelocity, singularity, eventhorizon
bigexplosion, protostars, dust, gas, stardying
creationcommingtoanend
creation, new, abundance, explosion, bright
theory, big, bang, explosion, galaxies
theory, creationoftheuniverse
huge, dumb, opinion, horrible, Godbetter
explosion, chaotic, false, bright, huge
big, boom, bang, bomb, blastoffcreatinguniverse
big, bang, me+hat=superman
confusing, interesting, birthofEarth
false, explosion, fire, nodinos
bang, big, theory, happenedrandomly
beginning, spark, life, center, boom
big, collision, formation, life, truth?
nothingtosetitinmotionbesidesGod
evolution, explosion, birthofEarth, basicelements, suddenexistenceoflife
starttime, beginning, kaboom, large, expansion
hydrogen, stars, formation, huge, theory
expandinguniverse, highdensity, temperature, Hubble, CMB
formation, theory, hydrogen, explosion, light
creation, universe, start, huge, all
bigbang, theory, hardtograsp, wheredidtheycomeupwiththis?, interesting
universe, cosmicinflation, photons, redshift, radiation
galaxies, CMB, antimatter, redshift, hotgas
beginning, cosmologicaltheory, GeorgesLemaitre, redshift, particleaccelerators
kaboom, planetscolliding, explosion, fireworks, TVshow
highdensity, hightemperature, galaxies
bang, bang, bang, bang, bang
universe, shifts, galaxies, temperature, particles
hotanddense, expandedrapidly, 14bya, redshift, spiralnebula
theory, God, explosion, first, beginning
dinosaurs, Earth, meteor, destruction, extinction
beginning, truth, veryveryveryveryhot, universe, awesome
theory, universe, stars, explosion, planets
beginning, universe, formation, cosmologicaltheory, development
universe, start, creation, explosion, TVshow
nice, beautiful, universal, explosion, fireworks
atheism, bang, creation, advanced, explosion
nothing, explosion, expansion, dust, stars
beginning, universe, explosion, existence, theory
14bya, cosmicbackgroundradiation, hotdensegas, appearstobe2.7K, didnotoccuratasingleplace

Online reading assignment question: big bang tags
(Fall semester 2009).
Online reading assignment question: big bang tags
(Spring semester 2010).

20101105

Overheard: extent of Milky Way

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

(Overheard following an introductory astronomy lecture-tutorial on the total vs. visible extent of the Milky Way.)

Instructor (to class): "So why do you think we can't see most of our Milky Way?"

Student 1: "Because it's so huge."

Instructor: "Then how it is possible that we can see distant galaxies outside the Milky Way?"

(Beat.)

Student 2: "Uh...because they're huge, too?"

20101104

Astronomy quiz question: neutron star in binary star system

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

A compact object with __________ may be evidence of a neutron star in a binary system.
(A) a hot, x-ray emitting accretion disk.
(B) regularly timed x-ray pulses.
(C) zero mass and no emitted light.
(D) repeated nova bursts.

Correct answer: (B)

Response (B) is evidence of a neutron star (pulsar) in a binary system; response (D) is evidence of a white dwarf in a binary system. Response (C) is not true for black holes (which have a finite mass, but zero size, and emit light from their accretion disks). Note that response (A) is also evidence of white dwarfs and black holes in binary systems, as they also have accretion disks.

Section 70158
(A) : 15 students
(B) : 24 students
(C) : 2 students
(D) : 3 students

"Success level": 59% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.81

20101103

Astronomy quiz question: type II supernova energy source

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

What provides the energy for a type II supernova explosion?
(A) Shockwaves from either nearby supernova explosions or hot young stars.
(B) Hydrogen fusion.
(C) Gravitational contraction.
(D) Convection.

Correct answer: (C)

Response (A) is how star formation may be triggered in the interstellar medium; response (D) is a consequence of heat from from the core to the surface of a star. Response (D) can no longer provide energy for a star at the end of its supergiant phase, as it core is iron at this point, past which requires more energy to be put in than can be released by fusion. Thus with no energy source to balance gravity, the core undergoes runaway contraction, and the resulting energy from this gravitational collapse of the core is transferred to the outer layers of the supergiant in an "implosion-explosion" sequence--a type II supernova.

Section 70158
(A) : 6 students
(B) : 5 students
(C) : 33 students
(D) : 0 students

"Success level": 77% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.83

20101102

Astronomy quiz question: black hole in binary star system

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

A compact object with __________ may be evidence of a black hole in a binary system.
(A) a hot, x-ray emitting accretion disk.
(B) regularly timed x-ray pulses.
(C) zero mass and no emitted light.
(D) repeated nova bursts.

Correct answer: (A)

Response (B) is evidence of a neutron star (pulsar) in a binary system; response (D) is evidence of a white dwarf in a binary system. Response (C) is not true for black holes (which have a finite mass, but zero size, and emit light from their accretion disks). Note that response (A) is also evidence of white dwarfs and neutron stars in binary systems, as they also have accretion disks.

Section 70160
(A) : 14 students
(B) : 4 students
(C) : 16 students
(D) : 0 students

"Success level": 46% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.78