Physics final exam question: larger versus smaller surface area coolers

Physics 205A Final Exam, Fall Semester 2009
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Multiple-Choice Question 14.5

[10 points.] A large styrofoam ice chest has warm temperatures outside, compared to its cold temperature contents. A small styrofoam ice chest has the same wall thickness, and the same warm temperatures outside and cold temperature inside. Which ice chest will have the greatest rate of heat entering its contents per time? Explain your answer using the properties of heat
conduction.

Solution and grading rubric:

• p = 10/10:
  Correct. Both coolers have the same temperature difference and thickness, but the larger cooler has more surface area, and thus has the smaller thermal resistance, and the greater rate of heat entering its contents per time. (Assuming that the larger cooler contains more cool substance that the smaller cooler, the larger cooler would take longer to warm up, due to the mass factor in Q = m*c*delta(T), but the relative amount of contents in the larger cooler does not affect the rate of heat entering its contents.)
  
• 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.
  
• v = 4/10:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Argues that the larger cooler will have a lesser rate of heat entering it per time, based on the mass of its conents.
  
• 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 72177
p: 11 students
r: 1 student
t: 0 students
v: 0 students
x: 0 students
y: 1 student
z: 0 students

Sections 70854, 70855
p: 31 students
r: 6 students
t: 0 students
v: 11 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 1337):

Another sample "p" response (from student 2962):

Yet another sample "p" response (from student 5051):

A sample "v" response (from student 1448):

Physics final exam question: warm aluminum, cold ice heat transfer

Physics 205A Final Exam, Fall Semester 2009
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 14.39

[Version 1]
[10 points.] An ice sample (0.0° C) is placed onto a 5.00 kg aluminum block at 1.0° C. As a result, the entire ice sample melts to 0.0° C water. As this system reached a thermal equilibrium of 0.0° C, was heat transferred from the ice sample to the aluminum block, or from the aluminum block to the ice sample, or were both transfers simultaneously taking place? Explain your answer using the properties of heat, temperature, and thermal equilibrium.

Solution and grading rubric:

• p = 10/10:
  Correct. Heat transfers from warmer to cooler temperature objects. The aluminum temperature decreases, and thus is losing heat, while the ice melts (while its temperature remains constant), and thus is gaining heat. Discusses how each object loses or gains heat, such that the direction of the transfer is certain.
  
• 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. May confuse heat with internal energy (heat transfers due to a difference in energy rather than temperature).
  
• t = 6/10:
  Nearly correct, but argument has conceptual errors, or is incomplete. Has heat flowing from aluminum to ice, but claims that internal energy of ice is unchanged (or Q_ice = 0) as its temperature remains constant.
  
• v = 4/10:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Has heat transferring from the ice to the aluminum, or has heat transferring from the aluminum causing the ice temperature to rise, or states that heat was transferred simultaneously from aluminum to ice and vice versa. At least has some discussion of temperature gradient, temperature/phase changes, and/or internal energy changes.
  
• x = 2/10:
  Implementation/application of ideas, but credit given for effort rather than merit. Statement of heat direction with little or substantive discussion.
  
• y = 1/10:
  Irrelevant discussion/effectively blank.
  
• z = 0/10:
  Blank.
  

Grading distribution:
Section 72177
p: 8 students
r: 0 students
t: 2 students
v: 1 student
x: 1 student
y: 1 student
z: 0 students

[Version 2]
[10 points.] An aluminum cylinder at room temperature (25.0° C) is dropped into a hole in a block of ice at 0.0° C. As this system reached a thermal equilibrium of 0.0° C, was heat transferred from the ice block to the aluminum cylinder, or from the aluminum cylinder to the ice block, or were both transfers simultaneously taking place? Explain your answer using the properties of heat, temperature, and thermal equilibrium.

Grading distribution:
Sections 70854, 70855
p: 28 students
r: 4 students
t: 8 students
v: 7 students
x: 1 student
y: 0 students
z: 0 students

A sample "p" response (from student 3334):

Another sample "p" response (from student 9626):

A sample "r" response (from student 0570):

A sample "t" response (from student 2468):

Another sample "t" response (from student 5256):

A sample "v" response (from student 1889):

Another sample "v" response (from student 4590):

Kudos: thanks and thanks again

"Thanks for the class" by Student 5454
Astronomy 210
December 2009
Cuesta College, San Luis Obispo, CA


"Have a good break" by Student 2685
Astronomy 210
December 2009
Cuesta College, San Luis Obispo, CA

Astronomy final exam question: making Pluto a planet (again)?

Astronomy 210 Final Exam, Fall Semester 2009
Cuesta College, San Luis Obispo, CA

[20 points.] Write down the three qualifications established by the International Astronomical Union for a planet. Discuss how one or more of these qualifications should be changed/eliminated such that Pluto would again be considered a planet.

(Photo credit: Untitled, Zara Evans, November 19, 2006, http://www.flickr.com/photos/zara/301724221/).

Solution and grading rubric:

• p = 20/20:
  Correct. Pluto already satisfies the first two IAU classification requirements (orbits the sun, and has spherical shape), but does not satisfy the third requirement, as Pluto does not clear/dominate its orbit. If this rule were eliminated, then Pluto would again become a planet.
  
• r = 16/20:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Instead of eliminating the third IAU requirement, argues that Pluto should instead satisfy it if were to somehow clear/domintate its orbit.
  
• t = 12/20:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. Problematic discussion, but at least understands IAU classification scheme.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Only partial understanding of IAU requirements.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit. Discussion of criteria unrelated to the IAU requirements.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 70160
p: 30 students
r: 5 students
t: 3 students
v: 2 students
x: 0 students
y: 1 student
z: 0 students

Section 70158
p: 40 students
r: 0 students
t: 0 students
v: 4 students
x: 1 student
y: 0 students
z: 2 students

A sample "p" response (from student 8260):

Another sample "p" response (from student 8624), with an appeal to the head of Abraham Lincoln:

A sample "r" response (from student 7094), where it would be easier to change Pluto's orbit than to change the IAU rules?

A sample "v" response (from student ):

Another sample "v" response (from student 2857):

A speculative "x" response (from student 2388):

Cf. a similar question (Cuesta College, Spring 2009) regarding Pluto's status in an earlier post:
Astronomy final exam question: Pluto not a planet?.

Astronomy final exam question: Venus vs. moon surface age

Astronomy 210 Final Exam, Fall Semester 2009
Cuesta College, San Luis Obispo, CA

[20 points.] Discuss whether Venus' surface is older or newer than the surface of the moon, and the evidence that supports this claim. Explain by comparing surface features of Venus with the moon.

Solution and grading rubric:

• p = 20/20:
  Correct. The number of impact craters on much greater on the moon, indicating its crust is much older than Venus', which has much fewer impact craters, having covered over much of its crust with extensive lava flows.
  
• 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. Recognizes importance of crater density, but may discuss how Venus' crust has more craters and thus is older, or correct choice for Venus' relative age, but crater discussion is problematic.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. At least recognizes that luminosity and temperature are relevant. May discuss Venus' atmosphere, runaway greenhouse effect, core, or other factors as evidence of its newer crust.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 70160
p: 23 students
r: 0 students
t: 14 students
v: 3 students
x: 1 student
y: 0 students
z: 0 students

Section 70158
p: 27 students
r: 4 students
t: 5 students
v: 5 students
x: 3 students
y: 1 student
z: 2 students

A sample "p" response (from student 1781):

An sample illustrated "p" response (from student 1964):

A more technical illusrated "p" response (from student 8260):

An sample "t" response (from student 6363), at least demonstrating the correlation between impact craters and surface age:

A sample "x" response (from student 2610), with a speculative guess followed by a sycophantic appeal:

Astronomy final exam question: water required for life?

Astronomy 210 Final Exam, Fall Semester 2009
Cuesta College, San Luis Obispo, CA

Water (or some other type of liquid) should be present on a planet harboring living things, as liquids are necessary to:
(A) transport nutrients and wastes.
(B) cause erosion.
(C) start tectonic plate motion.
(D) absorb radioactivity.

Correct answer: (A)

It is plausible that any form of life would require the ready transport of materials to and from and within itself to regulate chemical processes, which would require a liquid (such as, but not necessarily exclusively water).

Section 70158
(A) : 43 students
(B) : 2 students
(C) : 0 students
(D) : 2 students

Success level: 92% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0

Astronomy final exam question: halo stars likely for life?

Astronomy 210 Final Exam, fall semester 2009
Cuesta College, San Luis Obispo, CA

Halo stars of the Milky Way would not be likely places to find life because halo stars:
(A) are metal-poor.
(B) are not massive enough.
(C) are not old enough.
(D) have too much dark matter.

Correct answer (highlight to unhide): (A)

Halo stars are the first generation of stars born in the Milky Way, and thus would be metal-poor, as well as their planets, which would then not have "metals" (any elements heavier than hydrogen, which would include carbon and oxygen).

Section 70160
(A) : 27 students
(B) : 4 students
(C) : 4 students
(D) : 6 students

Success level: 69% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.11

Astronomy final exam question: rising waxing gibbous moon

Astronomy 210 Final Exam, Fall Semester 2009
Cuesta College, San Luis Obispo, CA

What time is it when the waxing gibbous moon is rising?
(A) 12:00 PM (noon).
(B) 3:00 PM (afternoon).
(C) 6:00 PM (sunset).
(D) 9:00 PM (evening).
(E) 12:00 AM (midnight).
(F) 3:00 AM (wee hours).
(G) 6:00 AM (sunrise).
(H) 9:00 AM (morning).

Correct answer: (B)

Note that response (D) (9:00 PM) is the time that the waxing gibbous moon would be highest overhead.

Section 70158
(A) : 0 students
(B) : 21 students
(C) : 1 student
(D) : 13 students
(E) : 0 students
(F) : 7 students
(G) : 2 students
(H) : 3 students

Success level: 51% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.31

Astronomy final exam question: evening setting moon

Astronomy 210 Final Exam, Fall Semester 2009
Cuesta College, San Luis Obispo, CA

Which phase will the moon be in if it is setting at 9:00 PM? Clearly circle your answer below.

Correct answer: (C) (Waxing crescent)

Note that response (A) (waxing gibbous) is the phase that the moon would be in if it is highest overhead at 9:00 PM.

Section 70160
(A) : 9 students
(B) : 2 students
(C) : 24 students
(D) : 1 student
(E) : 2 students
(F) : 1 student
(G) : 1 student
(H) : 0 students

Success level: 61% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.20

Astronomy quiz question: source of Neptune's atmospheric activity

Astronomy 210 Quiz 7, Fall Semester 2009
Cuesta College, San Luis Obispo, CA

The primary cause of Neptune's atmospheric activity is:
(A) liquid nitrogen and methane geysers.
(B) ammonia dissolved in the liquid mantle.
(C) a highly inclined magnetic field.
(D) its interior heat.

Correct answer: (D)

Atmospheric activity such as cyclones are caused by convection driven by the interior heat inside Jovian planets (i.e., The "Cream-in-Coffee Model").

Section 70160
(A) : 7 students
(B) : 7 students
(C) : 7 students
(D) : 20 students

Success level: 52% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.51

Astronomy quiz question: volcanic terrestrial planet?

Astronomy 210 Quiz 7, Fall Semester 2009
Cuesta College, San Luis Obispo, CA

A terrestrial planet __________ would be most likely to have active volcanoes today.
(A) close to the sun.
(B) that is massive.
(C) with a low density crust.
(D) with liquid metallic hydrogen.

Correct answer: (B)

Massive planets are will cool off at a slower rate than less-massive planets, such that it will retain more core heat, and more likely to be volcanically active in the present-day (i.e., The "Turkey/Cornish Hen Effect").

Section 70158
(A) : 8 students
(B) : 14 students
(C) : 17 students
(D) : 2 students

Success level: 38% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.50

Section 70160
(A) : 4 students
(B) : 24 students
(C) : 10 students
(D) : 3 students

Success level: 63% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.30

Astronomy quiz question: carbon dioxide sink

Astronomy 210 Quiz 7, Fall Semester 2009
Cuesta College, San Luis Obispo, CA

What prevents Earth's atmosphere from building up too much carbon dioxide?
(A) Volcanoes.
(B) Oceans.
(C) Plants.
(D) The greenhouse effect.

Correct answer: (B)

Oceans absorb vast amounts of carbon dioxide, which settle into sedimentary rocks on ocean floors, which are then subsequently subducted back into the mantle.

Section 70158
(A) : 0 students
(B) : 26 students
(C) : 15 students
(D) : 2 students

Success level: 65% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.75

Physics quiz question: cool metal, warm water heat exchange

Physics 205A Quiz 7, fall semester 2009
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Example 14.5

A 25 g iron sample at room temperature (25° C) is placed in 200 g of water at 80° C to reach thermal equilibrium. The specific heat of iron is 0.44 kJ/(kg·K). The specific heat of water is 4.19 kJ/(kg·K). The __________ had the greatest change in internal energy once thermal equilibrium is reached.
(A) 25 g iron sample.
(B) 200 g of water.
(C) (There is a tie.)
(D) (Not enough information is given.)

Correct answer (highlight to unhide): (C)

As the two components of this system reach thermal equilibrium, the amount of heat given up by the 200 g of water is exactly equal to the amount of heat taken in by the 25 g iron sample.

Student responses
Section 70854, 70855
(A) : 16 students
(B) : 16 students
(C) : 15 students
(D) : 0 students

Success level: 31%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.42

Physics quiz question: same-temperature, different-mass heat exchange

Physics 205A Quiz 7, fall semester 2009
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Example 14.5

A 25 g iron sample and a 100 g iron sample are both at room temperature (25° C). The specific heat of iron is 0.44 kJ/(kg·K). When the 25 g iron sample and the 100 g iron sample are brought in contact with each other, heat is transferred from the __________ to the __________.
(A) 25 g iron sample; 100 g iron sample.
(B) 100 g iron sample; 25 g iron sample.
(C) (Both of the above choices.)
(D) (None of the above choices.)
(E) (Not enough information is given.)

Correct answer (highlight to unhide): (D)

Even though the 100 g iron sample has more internal energy than the 25 g iron sample, they are at the same temperature and thus will already be at thermal equilibrium when brought together in contact with each other, such that no heat will be exchanged between them.

Student responses
Section 72177
(A) : 0 students
(B) : 3 students
(C) : 2 students
(D) : 6 students
(E) : 0 students

Success level: 54%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.50

Astronomy current events question: youngest brown dwarf

Astronomy 210L, Fall Semester 2009
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, "Spitzer Telescope Observes Baby Brown Dwarf," November 23, 2009
http://www.astronomy.com/asy/default.aspx?c=a&id=8846

The NASA Spitzer Space Telescope has discovered the youngest brown dwarf ever observed, which is:
(A) cooler and lighter than a star, but heavier and warmer than a jovian planet.
(B) an extremely old white dwarf.
(C) an almost failed black hole.
(D) theoretically composed of dark matter.
(E) a star with a high proportion of dusty material.

Correct answer: (A)

Student responses
Sections 70178, 70186, 70200
(A) : 20 students
(B) : 3 students
(C) : 1 student
(D) : 2 students
(E) : 3 students

Astronomy current events question: Enceladus geysers

Astronomy 210L, Fall Semester 2009
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!)

Alan MacRobert, "Cassini Visits a Science-Fiction World," November 23, 2009
http://www.skyandtelescope.com/news/71703192.html

The newest images from the Cassini space probe of Saturn's moon, Enceladus, show:
(A) a newly discovered ring system.
(B) large mats of photosynthesizing algae.
(C) erupting water vapor and dust geysers.
(D) recent tectonic ice motion.
(E) water circulating under sections of transparent ice.

Correct answer: (C)

Student responses
Sections 70178, 70186, 70200
(A) : 4 students
(B) : 2 students
(C) : 18 students
(D) : 4 students
(E) : 5 students

FCI post-test comparison: Cuesta College (SLO/NC campuses) versus UC-Davis

Students at both North County (Paso Robles) and San Luis Obispo campuses of Cuesta College (San Luis Obispo, CA) and the University of California at Davis were administered the Force Concept Inventory (Hestenes, Wells, and Swackhamer, 1992) during the last week of instruction, in order to follow up on the pre-test results from the first week of instruction (which showed no statistical difference between pre-test scores between NC and SLO campus students, and between these Cuesta students (pooled together into one population) and UC-Davis students).

The post-test FCI results of NC and SLO campus students can be compared to each other.

     Cuesta College    Cuesta College    
     Physics 205A      Physics 205A
     Fall Semester     Fall Semester
     2009 NC           2009 SLO
N    13 students*      43 students*
low   8                 3
mean 18.5 +/- 6.9      13.2 +/- 5.7
high 26                28

*Excludes students with negative informed consent forms (*.pdf)

Note the higher mean score for NC campus students over SLO campus students; a "Student" t-test of the null hypothesis results in p = 0.0077, thus there is a highly significant difference between NC and SLO campuses of Cuesta College.

The post-test FCI results of NC campus students and SLO campus students can then be compared separately with UC-Davis students. First the NC students are compared with UC-Davis students:

     Cuesta College    UC-Davis
     Physics 205A      Physics 7B
     Fall Semester     Summer Session II
     2009              2002
N    12 students       76 students
low   8                 3
mean 18.5 +/- 6.9      12.9 +/- 5.5
high 26                26

A "Student" t-test of the null hypothesis results in p = 0.0017, thus there is a highly significant difference between NC campus and UC-Davis FCI post-test scores.

The pre- to post-test gain for NC campus students for this semester at Cuesta College is:

Physics 205A Fall Semester 2009 section 72177
<initial%> = 38% +/- 19% (N = 17)
  <final%> = 62% +/- 23% (N = 13)
       <g> = 0.37 +/- 0.23 (matched-pairs); 0.38 (class-wise)

In contrast to the SLO campus students (results below), the NC campus Hake gain is much higher than historical previous semester's results at Cuesta College in classes that have used think-(pair)-share methods (0.21-0.33), as well as radically restructured discussion/laboratory courses at UC-Davis (0.16), and conventional lecture-centric calculus-based introductory physics at Cuesta College (0.14-0.16), as discussed in previous postings on this blog. (Note that Hake gains of 0.00-0.30 are considered low-gain, 0.30-0.70 are medium-gain, and 0.70-1.00 are high-gain.)

Next the SLO campus students are compared with UC-Davis students:

     Cuesta College    UC-Davis
     Physics 205A      Physics 7B
     Fall Semester     Summer Session II
     2009              2002
N    43 students       76 students
low   3                 3
mean 13.2 +/- 5.7      12.9 +/- 5.5
high 28                26

A "Student" t-test of the null hypothesis results in p = 0.77, thus there is no significant difference between SLO campus and UC-Davis FCI post-test scores.

The pre- to post-test gain for SLO campus students for this semester at Cuesta College is:

Physics 205A Fall Semester 2009 sections 70854, 70855
<initial%> = 32% +/- 15% (N = 58)
  <final%> = 44% +/- 19% (N = 43)
       <g> = 0.17 +/- 0.24 (matched-pairs); 0.18 (class-wise)

This Hake gain for the SLO campus students is much lower than other think-(pair)-share courses at Cuesta College, but at least comparable to the radically restructured discussion/laboratory courses at UC-Davis, and conventional lecture-centric calculus-based introductory physics at Cuesta College.

Previous FCI results for think-(pair)-share Physics 205A classes:

• Cuesta College versus UC-Davis, Fall semester 2009 pre-tests.
  
• Cuesta College versus UC-Davis, Spring semester 2009 pre-tests and post-tests.
  
• Cuesta College versus UC-Davis, Fall semester 2008 pre-tests and post-tests.
• Cuesta College versus UC-Davis, Spring semester 2008 pre-tests and post-tests.
• Cuesta College versus UC-Davis, Fall semester 2007 pre-tests and post-tests.

Astronomy current events question: T2K neutrino experiment

Astronomy 210L, Fall Semester 2009
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, "Neutrino Experiment Starts Its Search for the Unknown," November 24, 2009
http://www.astronomy.com/asy/default.aspx?c=a&id=8848

The T2K (Tokai-to-Kamioka) experiment in Japan will measure properties of neutrinos by:
(A) counting solar neutrinos detected in Tokai and Kamioka at the same time.
(B) shooting neutrinos underground from Tokai to a detector in Kamioka.
(C) comparing neutrinos made in Tokai to identical twins made in Kamioka.
(D) counting neutrinos that survive after being airlifted from Tokai to Kamioka.
(E) shooting neutrinos from Tokai and Kamioka to collide in the upper atmosphere.

Correct answer: (B)

Student responses
Sections 70178, 70186, 70200
(A) : 11 students
(B) : 22 students
(C) : 12 students
(D) : 6 students
(E) : 10 students

Astronomy current events question: Eta Carinae supernova imminent?

Astronomy 210L, Fall Semester 2009
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, "A Rogue Star Going Wild?," November 26, 2009
http://www.skyandtelescope.com/news/home/75160377.html

What observations by the Hubble Space Telescope Imaging Spectrograph indicate that the stars in the binary star system Eta Carinae may soon explode as type II supernovas?
(A) Size of both stars have suddenly collapsed.
(B) Size of both stars have increased, merging them together.
(C) Increase in x-rays where their outflowing winds collide.
(D) Neighboring star's supernova shockwave will soon hit Eta Carinae.
(E) Orbits of both stars are spiraling even closer.

Correct answer: (C)

Student responses
Sections 70178, 70186, 70200
(A) : 9 students
(B) : 11 students
(C) : 27 students
(D) : 4 students
(E) : 11 students

Astronomy current events question: LCROSS debris analyzed

Astronomy 210L, Fall Semester 2009
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, "LCROSS Impact Kicked up Lunar Water," November 13, 2009
http://www.skyandtelescope.com/community/skyblog/newsblog/69991547.html

Data analyzed from the NASA Lunar Crater Observation and Sensing Satellite (LCROSS) has determined that debris from an empty Centaur rocket booster that impacted the Moon contains:
(A) water vapor.
(B) dark matter.
(C) radioactive fallout from a thermonuclear detonation.
(D) organic compounds.
(E) carbon nanotubes.

Correct answer: (A)

Student responses
Sections 70178, 70186, 70200
(A) : 43 students
(B) : 1 students
(C) : 1 students
(D) : 3 students
(E) : 3 students

Astronomy current events question: Cassiopeia A neutron star

Astronomy 210L, Fall Semester 2009
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, "Carbon Atmosphere Discovered on Neutron Star," November 4, 2009
http://www.astronomy.com/asy/default.aspx?c=a&id=8771

What have University of Alberta researchers determined about the Cassiopeia A neutron star, using results from the Chandra X-ray Observatory?
(A) Has a thin coating of carbon.
(B) On the verge of imploding, becoming a black hole.
(C) Has zero spin.
(D) Transparent to certain types of x-rays.
(E) Has not actually exploded yet, due to the finite speed of light.

Correct answer: (A)

Student responses
Sections 70178, 70186, 70200
(A) : 38 students
(B) : 5 students
(C) : 4 students
(D) : 2 students
(E) : 0 students

Astronomy current events question: Spirit rover stuck

Astronomy 210L, Fall Semester 2009
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, "NASA to Begin Attempts to Free Sand-Trapped Mars Rover," November 12, 2009
http://www.astronomy.com/asy/default.aspx?c=a&id=8811

How do NASA engineers plan to free the Mars exploration rover Spirit from being stuck in sand?
(A) Using its scoop to dig a trench out of the sand.
(B) Waiting until the martian winter hardens the sand.
(C) Carefully monitoring the results of spinning all wheels at the same time.
(D) Pushing on a nearby boulder with its robotic arm to gain traction.
(E) The exploration rover Opportunity will give it a push.

Correct answer: (C)

Student responses
Sections 70178, 70186, 70200
(A) : 10 students
(B) : 5 students
(C) : 27 students
(D) : 6 students
(E) : 3 students

Online reading assignment question: Venus, Mars tags

Astronomy 210, Fall Semester 2009
Cuesta College, San Luis Obispo, CA

091202-venustags
http://www.flickr.com/photos/waiferx/4154253710/
Originally uploaded by Waifer X

Wordle.net tag cloud for "Venus" generated by responses from Astronomy 210 students at Cuesta College, San Luis Obispo, CA (http://www.wordle.net/show/wrdl/1404478/Untitled).


091202-marstags
http://www.flickr.com/photos/waiferx/4153493501/
Originally uploaded by Waifer X

Wordle.net tag cloud for "Mars" generated by responses from Astronomy 210 students at Cuesta College, San Luis Obispo, CA (http://www.wordle.net/show/wrdl/1404592/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.

(The following question was asked prior to lectures on the terrestrial planets.)

Write down five words that describe or are associated with "Venus." Keep word phrases together with no spaces between them (e.g., "veryhot"). (Graded for completion.)

Student responses
Sections 70158, 70160

womenarefrom williams planet terrestrial bright
neighbor hot dry large secondplanet
love beauty hot ishtar
crazy wild faraway cold icy wet
volcanic love hot lifeless golde brown
Earth cloudy hot dense noair
sexy hot steaming sweaty planet
hot rocky bright terrestrial nearsun
blue Earthstwin gases big green
noocean denseatmosphere greenhouse hottesttemperature sulfuricacid
gas Earthstwin veryhot secondplanet storms
veryhot
hot sister similarsize red langdon
close veryhot razor greekgod red
razors women hot sexy green
bright morningstar Earthstwin CO2 rocky
sister goddess sulfuricacid second deadly
space dark tennis Serena Mars
secondplanetfromthesun
volatileatmosphere terrestrial large greenplanet bright
yourfireyourdesirerazor
veryhot brighteststar secondclosestplanettothesunbetweenusandmercury volcanoes volatile
bad
razors williamssister volcanic CO2 224dayorbit
hot secondplanet veryhot planet razor
razorforwomen romangoddess tennisstar planet cloudy
planet mediumsize warm dead rocky
love god razors women sunev
green earthsize-ish love razors secondrockfromsun
rockband scubadiving intergalactic skivveys michaelbay
women terrestrial lifeless Earthsized plain
hot planet secondplanet terrestrial sisterplanet
secondplanet visible hot venus
hotasamuthafer
veryhot closetosun orbitssun morningstar sisterplanet
venereal goddessoflove Earthsisterplanet sulfuricacidclouds
women hot planet large yellow
love golden hot blue sister
razors badass moo meow POW!
Hell extremelyhot greenhouse deadly smelly
women hot razor boiling planet
secondclosest sisterplanet carbondioxide inferiorplanet solarwind
thickatmospherethatishot
planet Earth big hot round
veryhot gas planet active
Hades desert carbondioxide unpleasant thickclouds
hotdeserts Hades carbondioxide deadly unpleasant
cloudy dry acid male hot
hot second terrestrial planet sister
hot gas earth methane wrinkly
morningstar hotatmosphere greekgoddess planet
carbondioxide hot smelly thickair deadly
venus fire space planet stars
orange love aphrodite women hot sexy
flytrap veryhot largegas
hottestatmosphere closertothesun hot terrestrialplanet
twin flytrap razors gassy unreachable
terrestrialplanet rock hot nearsun redish
razors chicks planets hot jovian
aphrodite notoftenvisible female hot small
hot beautiful toxic terrestrial planet
second hot bright rocky sisterplanet
goddessoflove verydense
verybig planet terrestrial hot biggerthanthemoon
razors womenarefrom veryhot terrestrial planet
womenarefrom razors cloudy volcanoes solidifiedlavaflows
greenhouse earthsize hot
hot thickatmosphere lotsofclouds volcanoes sulfur
almostsamemassasearth biggercore CO2atmosphere thinatmosphere veryhot
veryhot rotatesoppositedirection denseclouding volcanoes sisterplanettoearth
red orange redhot hot flaming
goddess love planet sky night
song
barren veryhot planet brown closeby
cool white dense carbondioxide round
intenseatmosphere crushing girls superhot secondplanet
sisterplanet equalsize hot goddess acidrain

Write down five words that describe or are associated with "Mars." Keep word phrases together with no spaces between them (e.g., "redplanet"). (Graded for completion.)

Student responses
Sections 70158, 70160

redplanet fourth Earthlike menarefrom martians
neighbor coolerthanearth life fourthplanet large
war red ice candybars martian
redplanet aliens stormy water movies
red aliens wild notlivable
small red dead far, round
red liveable water thinatmosphere cold
chocolateygoodness bar yumyum
fourthplanet cool MarsAttacks dead Earthtwin
aliens red small hot crators
rangingtemperatures thinatmosphere polarice carbondioxide martians
desert redplanet candybar movies mountain
verycold
red space astronaut NASA rover
red volcanoes menarefrom closeproximity rocky
dust TotalRecall red aliens hot
Craters volcanoes deserts twomoons thinatmosphere
redplanet futurecolony rovers fourthplanet mysterious
candybars space holes TotalRecall
fourthplanetfromthesun
dirt volcanoes colonize crimson rovers
aliens live twin candy planet
fourthplanet rocky possiblelife rover ice
YA
candybars Ares l Phobos Deimos
fourthplanet red MarsAttacks volcano fourth
candy TVshow godofwar reddish volcanoes
hot red mediumsize sunny rocky
men candy Marvin sram red
candybar martian Marvin redplanet cold
thehumantorchwasdeniedabankloan candy bouncedchecks crackbaby journey
men small terrestrial
martians redplanet fourthplanet terrestrial basalt
martians red fourthplanet Marvin
redplanet itsgotice
redplanet fourthfromthesun terestrialplanet deserts valleys
verysmall godofwar ironoxide Phoenixmarslander Phobos Deimos
men red planet small CO2
cold dryworld small frozen moonplanet
red hot second dead boring
godofwar redplanet ironoxide impactcraters OlympusMons
red planetthatsfurthest terrestrial
aliens smaller round planet Earth
hot planet red activevolcano
craters permafrost shieldvolcanoes Earthlike cold
craters cold dry ice little water
red dust face RedFaction Marvin
red twomoons ice microbiclife small
terrestrial planet red fourth rover
red dirt TotalRecall nooxygen martians
marsrover red terrestrial boysarefrom planet
cold craters maria thinair thickcrust
bars moons water life tests
Ares men war red boring
red planet saucer martians UFOs mission
red planet terrestrial colder water?
red Bradbury cheeky desert dusty
terrestrialplanet rocky lesshot nearsun reddish orangeish
Aliens SpaceJam MichaelJordan basketball sports
male Ares red volcanic hot
red dry boring lame whatever
earth red ice rover forth
godofwar verylittlewater
dustlike rock terrestrial biggerthanmercury red
marsbars menarefrom redplanet terrestrial planet
menarefrom marscandybars rocky permafrost volcanoes
red cold small terraform rust
godofwar icycold polarcaps permafrost red
verycold ice thinatmosphere somehydrogen butmostly CO2
redplanet mountian plains ridges dunes craters
redplanet small tiny little red
MarsAttacks aliens red volcano rover
men
red closeby dormant expeditions candy
red iron candybars Deimos Phobos
red fourthplanet volcanoes big fun
war terraform redplanet rover cold
red small brother desert cool
bars candy chocolate red notbadassasVenus

Physics midterm problem: copper cylinder suspended in air, and in oil

Physics 205A Midterm 2, Fall Semester 2009
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 9.35

[20 points.] A copper cylinder (density 8.92e+3 kg/m^3) weighs 12.5 N when suspended from a scale in air. When this same cylinder is completely submerged in oil while suspended from a scale, the scale reading is 9.5 N. Find (a) the volume of the cylinder, and (b) the density of the oil. Show your work and explain your reasoning.

Solution and grading rubric:

• p = 20/20:
  Correct. Applies Newton's first law for the cylinder in air equating tension and weight to find mass, then finds volume V = m/rho_Cu = 1.4e-4 m^3. Applies Newton's first law for the cylinder in oil equating the upwards forces T = 9.5 N and F_B = rho_oil*g*V with the downwards weight (which is still 12.5 N), to solve for rho_oil = (w - T)/(g*V) = 2.1e+3 kg/m^3.
  
• r = 16/20:
  Nearly correct, but includes minor math errors.
  
• t = 12/20:
  Nearly correct, but approach has conceptual errors, and/or major/compounded math errors. Solves for volume using F_B = rho*g*V where F_B is 3.0 N, but rho is the density of water, or copper(!).
  
• v = 8/20:
  Implementation of right ideas, but in an inconsistent, incomplete, or unorganized manner. Applies specific gravity definition rho_object/rho_fluid = V_submerged/V_total to solve for the density of the oil and/or the cylinder volume, or uses P_2 = P_1 + rho*g*d.
  
• 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 72177
p: 4 students
r: 1 students
t: 3 students
v: 5 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 7575):

Astronomy midterm question: supergiant seen as a main-sequence star?

Astronomy 210 Midterm 2, fall semester 2009
Cuesta College, San Luis Obispo, CA

Discuss how it would be possible to observe a massive star during its main-sequence lifetime, while this star is actually a supergiant. Explain using the properties of mass and stellar lifetimes, and light.

Solution and grading rubric:

• p:
  Correct. Explains how the finite speed of light causes distant objects to appear as they did in the past, such that a massive star will still appear to be in its main-sequence lifetime, despite having already become a supergiant.
  
• r:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. At least recognizes that distant objects appear as they do in their past, or that the vast distances and/or finite speed of light is relevant.
  
• t:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors.
  
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Discussion based on short lifetimes, bright luminosities, and/or fast fusion rates of massive stars.
  
• x:
  Implementation/application of ideas, but credit given for effort rather than merit. Implausible evidence/methods/discussion.
  
• y:
  Irrelevant discussion/effectively blank.
  
• z:
  Blank.
  

Grading distribution:
Section 70160
p: 22 students
r: 5 students
t: 0 students
v: 15 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 7272):

Astronomy midterm question: mass is density

Astronomy 210 Midterm 2, Fall Semester 2009
Cuesta College, San Luis Obispo, CA

[20 points.] Consider the following comment:

"The mass of a star is the physical characteristic that, more than anything else, determines how the star will go through its life. Mass is destiny for a star."
—Keivan Stassun (Jeanna Bryner, "Twin Stars Born 500,000 Years Apart," June 28, 2008, http://www.foxnews.com/story/0,2933,370244,00.html)

Discuss how the luminosity and the lifetime of a star are both related to its mass. Explain using the properties of stars.

Solution and grading rubric:

• p = 20/20:
  Correct. A massive star has greater gravitational forces that must be supported by greater internal pressures (hydrostatic equilibrium), which results in higher rates of fusion, and thus bright luminosities and shorter lifetimes. May motivate higher fusion rates and shorter lifetimes or massive stars due to the rate of energy released due to its bright luminosity.
  
• 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. At least recognizes that luminosity, lifetime and mass are correlated to each other, but does not explicitly connect all three.
  
• v = 8/20:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner.
  
• x = 4/20:
  Implementation/application of ideas, but credit given for effort rather than merit. Implausible evidence/methods/discussion.
  
• y = 2/20:
  Irrelevant discussion/effectively blank.
  
• z = 0/20:
  Blank.
  

Grading distribution:
Section 70160
p: 34 students
r: 2 students
t: 5 students
v: 1 student
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 1836):

Another sample "p" response (from student 2662), with a whimsical illustration:

Another sample "p" response (from student 0889), who manages to pull it off at the last minute:

Astronomy midterm question: Acrux misprint?

Astronomy 210 Midterm 2, fall semester 2009
Cuesta College, San Luis Obispo, CA

Information regarding the star Acrux from an astronomy textbook[*] is shown below.

Apparent magnitude (m): +0.90
Distance: 80 parsecs (260 light years)
Absolute magnitude (M): +3.5

Discuss whether or not the absolute magnitude value of M = +3.5 for Acrux has been misprinted, and how you know this. Explain using the properties of apparent magnitude, absolute magnitude, and distance.

[*] Michael A. Seeds and Dana E. Backman, Perspectives in Astronomy, 1/e, Thomson Brooks/Cole (2008), p. 338 (Table A-6).

Solution and grading rubric:

• p:
  Correct. Apparent magnitude is how bright the star appears at its real distance of 80 parsecs away; absolute magnitude (its intrinsic brightness) is how the bright the star would be if brought to the "fair distance" of 10 parsecs. Bringing a star that is farther away than 10 parsecs to this fair distance should result in a absolute magnitude brighter, not dimmer than its apparent magnitude. Since Acrux's absolute magnitude M = +3.5 (at 10 parsecs) is dimmer than its apparent magnitude m = +0.90 (at 80 parsecs), the absolute magnitude must be incorrect (as it is expected to be brighter than +0.90). May instead argue that distance is misprinted, but at least recognizes discrepancy in how m, M, and d are related. (Cf. wikipedia.org/wiki/Alpha_Crucis, where Acrux has a distance of 99 ± 5 parsecs, an apparent magnitude of +0.77 and an absolute magnitude of –4.14.)
  
• r:
  Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Does not clearly explain why d, m, M data is inconsistent, but at least indicates that m and M are "switched," the distance must be much smaller, etc.
  
• t:
  Contains right ideas, but discussion is unclear/incomplete or contains major errors. May switch definitions of m and M and/or state data is correct, but at least distinguishes between brightnesses that are seen and are intrinsic.
  
• v:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Garbled definitions/relations between d, m, and M.
  
• 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: 27 students
r: 5 students
t: 6 students
v: 0 students
x: 3 students
y: 0 students
z: 1 student

A sample "p" response (from student 1543):
A sample "x" response (from student 6307):
Another sample "x" response (from student 6364):

Physics midterm problem: string standing waves

Physics 205A Midterm 2, fall semester 2009
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 11.49

A string is attached with a length of 0.80 m between supports and is stretched by a 4.5 kg hanging mass at one end. A function generator oscillates the string at its fundamental frequency of 170 Hz. Find (a) the linear mass density of the string, and (b) the mass that should hang off of the string such that the same 170 Hz frequency vibrates the n = 3 mode (as shown below). Show your work and explain your reasoning using the properties of wave speeds, periodic waves, and standing waves.


Solution and grading rubric:

• p:
  Correct. Mass of the string is not provided. However, f₁ = 170 Hz, L = 0.80 m, such that v = 272 m/s. With v and tension F = m·g = 44.1 N (where m is the hanging mass, not the string mass), linear mass density = 6.0×10⁴ kg/m. Then with a new situation, f₃ = 170 Hz = 3·f_1,new , and with L and the linear mass density the same as before, then the new hanging mass m_new = 0.50 kg. Or argues that for frequency to remain at 170 Hz, while n increases by a factor of three, the new wave speed must be reduced by a factor of three, such that the tension and the hanging mass must be reduced by a factor of nine.)
  
• r:
  Nearly correct, but includes minor math errors. Correctly finds the linear mass density of the string (or may have omitted a factor of g = 9.80 m/s²), but instead has wave speed increased by a factor of three, and thus the hanging mass increases by a factor of nine, or 40.5 kg (or similar increase).
  
• t:
  Nearly correct, but approach has conceptual errors, and/or major/compounded math errors. Typically finds linear mass density as (4.5 kg)/(0.80 m) = 5.6 kg/m, or confounds mu with mass, velocity with frequency, etc., but still has systematic attempt at finding linear mass density from original n = 1 case, and then feeds (erroneous) linear mass density into the n = 3 case, along with other algebraic or nomenclature errors.
  
• v:
  Implementation of right ideas, but in an inconsistent, incomplete, or unorganized manner. Involves mass-spring or pendulum period equations.
  
• x:
  Implementation of ideas, but credit given for effort rather than merit.
  
• y:
  Irrelevant discussion/effectively blank.
  
• z:
  Blank.
  

Grading distribution:
Sections 70854, 70855
p: 4 students
r: 11 students
t: 23 students
v: 10 students
x: 1 student
y: 0 students
z: 0 students

A sample "p" response (from student 2323):

Physics midterm problem: categorizing a cart collision

Physics 205A Midterm 2, fall semester 2009
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 7.47

A 0.300 kg cart traveling in the +x direction at 0.20 m/s collides with a 0.500 kg cart that is initially at rest. The carts are not stuck together after the collision. After the collision, the 0.500 kg cart (that was initially at rest) travels in the +x direction at 0.15 m/s. Neglect drag and friction. Find (a) the final velocity of the 0.300 kg cart, and (b) classify this collision as elastic, inelastic, or completely inelastic. Show your work and explain your reasoning.


Solution and grading rubric:

• p:
  Correct. Finds final speed of the 0.300 kg cart, using conservation of momentum (as there is neither drag nor friction), v_f1 = -0.050 m/s. It is not known whether the carts are permanently deformed and/or energy was lost to thermal/sound systems, so collision could be either inelastic or elastic (but cannot be completely inelastic because the carts are not stuck together after the collision). Explicitly tests for whether or not kinetic energy is conserved, and finds that since kinetic energy is conserved, this collision must be elastic.
  
• r:
  Nearly correct, but includes minor math errors. As (p), but misinterprets collision as being completely inelastic, but at least applies momentum conservation to find the correct v_f1 for the case where the carts are stuck together, then shows that kinetic energy was not conserved for this stuck-together collision.
  
• t:
  Nearly correct, but approach has conceptual errors, and/or major/compounded math errors. Has correct v_f1 (may have magnitude only) from momentum conservation, but does not explicitly test for energy conservation, and attempts to identify collision as elastic or inelastic solely on the basis of no visible deformation, which is not explicitly stated.
  
• v:
  Implementation of right ideas, but in an inconsistent, incomplete, or unorganized manner. Application of momentum conservation, but v_f1 is incorrect, with little or no test of kinetic energy conservation.
  
• x:
  Implementation of ideas, but credit given for effort rather than merit. Discussion based on stated characteristics of collision, with no application or test of appropriate conservation laws.
  
• y:
  Irrelevant discussion/effectively blank.
  
• z:
  Blank.
  

Grading distribution:
Sections 70854, 70855
p: 7 students
r: 2 students
t: 31 students
v: 7 students
x: 2 students
y: 0 students
z: 0 students

A sample "p" response (from student 5446), testing for kinetic energy conservation after applying momentum conservation:

Physics midterm question: block versus cylinder

Physics 205A Midterm 2, fall semester 2009
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 6.28, Problem 8.60

[10 points.] A block and a cylinder of the same mass both start from rest and respectively slide or roll without slipping down identical ramps. Which object (if any) has a faster speed at the bottom of the ramp, 0.50 m below their starting points? Neglect drag and friction. Explain your answer using energy conservation and properties of rotating/rolling objects.

Solution and grading rubric:

• p = 10/10:
  Correct. Both objects undergo the same decrease in potential energy, which all goes into translational kinetic energy for the block, but this potential energy must go into both translational kinetic energy and rotational kinetic energy for the cylinder, and thus the cylinder will have slower translational speed.
  
• 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. Accounts for rotational kinetic energy for the cylinder, but concludes that will be moving faster.
  
• t = 6/10:
  Nearly correct, but argument has conceptual errors, or is incomplete. Neglects to include rotational kinetic energy for the cylinder, but at least uses energy conservation.
  
• v = 4/10:
  Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Uses methods other than a systematic application of energy conservation.
  
• 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 72177
p: 2 students
r: 5 students
t: 6 students
v: 0 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 4747):
A sample "t" response (from student 1445):