P-dog's blog: boring but important: 200910

20091031

Astronomy current events question: Europa subsurface ocean oxygen?

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, "Europa Ocean May Contain Enough
Oxygen to Support Life," October 9, 2009
http://www.astronomy.com/asy/default.aspx?c=a&id=8706

According to a University of Arizona researcher, what is the proposed source for oxygen that may be found in the subsurface oceans of Jupiter's moon, Europa?
(A) Charged particles impacting its icy surface.
(B) Water- and oxygen-rich asteroids.
(C) Open vents in the ice.
(D) Exotic chemical processes on the warm ocean floor.
(E) Photosynthesis.

Correct answer: (A)

Student responses
Sections 70178, 70186, 70200
(A) : 16 students
(B) : 7 students
(C) : 13 students
(D) : 18 students
(E) : 2 students

Astronomy current events question: solar system edge discovery

Clara Moskowitz, "Mystery Emissions Found at Solar System Edge," October 15, 2009
http://www.msnbc.msn.com/id/33332042/ns/technology_and_science-space/

What did the NASA Interstellar Boundary Explorer probe recently find at the edge of the solar system?
(A) Rapidly deteriorating heliosphere.
(B) Large planetoid that will pass close by in late 2012.
(C) Ion trails left by the Pioneer 10/11 and Voyager 1/2 probes.
(D) Ribbon of energetic neutral particles.
(E) Diffuse shell of dark matter.

Correct answer: (D)

Student responses
Sections 70178, 70186, 70200
(A) : 3 students
(B) : 3 students
(C) : 6 students
(D) : 43 students
(E) : 0 students

Astronomy current events question: James Webb Space Telescope

Astronomy.com editors, "Test Model of James Webb Space Telescope Instrument Ready," October 14, 2009
http://www.astronomy.com/asy/default.aspx?c=a&id=8714

What mission is the joint NASA/European Space Agency James Webb Space Telescope planned to replace?
(A) Cancelled Mars sample return mission.
(B) Repaired Hubble Space Telescope.
(C) Failed Indian Space Agency Chandrayaan moon probe.
(D) Recently crashed LCROSS probe.
(E) Spitzer Space Telescope, out of coolant.

Correct answer: (B)

Student responses
Sections 70178, 70186, 70200
(A) : 0 students
(B) : 28 students
(C) : 5 students
(D) : 8 students
(E) : 14 students

20091025

Astronomy current events question: LCROSS mission outcome

Alan MacRobert, "The LCROSS Impact, Continued," October 11, 2009
http://www.skyandtelescope.com/news/home/63766222.html

What was the somewhat unexpected result of the NASA LCROSS mission lunar impact?
(A) No collision was observed.
(B) The impact was smaller than expected.
(C) Evidence of liquid water waves.
(D) A new faint, tilted ring surrounding the Moon.
(E) Brief disruption in satellite TV communications.

Correct answer: (B)

Student responses
Sections 70178, 70186, 70200
(A) : 4 students
(B) : 20 students
(C) : 5 students
(D) : 0 students
(E) : 0 students

Astronomy current events question: First Family star party

Kelly Beatty, "Stargazing with the Obamas," October 8, 2009
http://www.skyandtelescope.com/news/63749172.html

What was the special occasion commemorated by the White House Star Party, which was attended by the President and the First Lady?
(A) Washington D.C. Light Pollution Darkout 2009.
(B) 2009 Nobel Peace Prize.
(C) NASA LCROSS mission lunar impact.
(D) Renovation of the White House Observatory.
(E) International Year of Astronomy 2009.

Correct answer: (E)

Student responses
Sections 70178, 70186, 70200
(A) : 17 students
(B) : 4 students
(C) : 8 students
(D) : 4 students
(E) : 22 students

Astronomy current events question: Saturn's new ring system

Kelly Beatty, "Saturn's New King of the Rings," October 7, 2009
http://www.skyandtelescope.com/news/63685982.html

According to University of Virginia researchers, what is the source of Saturn's newly discovered tilted ring system?
(A) Captured asteroids.
(B) Material from one of its moons.
(C) A disintegrated comet.
(D) Magnetic storm eruptions.
(E) Solar winds.

Correct answer: (B)

Student responses
Sections 70178, 70186, 70200
(A) : 6 students
(B) : 39 students
(C) : 4 students
(D) : 4 students
(E) : 3 students

Astronomy current events question: MESSENGER final destination

Kelly Beatty, "Messenger's Third "Taste" of Mercury," September 29, 2009
http://www.skyandtelescope.com/news/62766047.html

The NASA MESSENGER spacecraft recently made a third and final flyby past Mercury. What is its final destination in 2011?
(A) Orbiting around Mercury.
(B) Flying through a solar flare.
(C) Crashing into a shadowed crater on Mercury.
(D) Polar orbit around the Sun.
(E) Asteroid 7861 Messenger.

Correct answer: (A)

Student responses
Sections 70178, 70186, 70200
(A) : 16 students
(B) : 2 students
(C) : 4 students
(D) : 4 students
(E) : 0 students

20091020

Astronomy in-class activity: OBAFGKM poetry slam (NCC)

Astronomy 210, Fall Semester 2009
Cuesta College, San Luis Obispo, CA
(North County Campus)

Astronomy 210 In-class activity 14: OBAFGKM Poetry Slam

Students were instructed to use at least OBAFGKM, and/or part or all of the additional OBAFGKMRNSC or OBAFGKMLT extensions to individually write an original, coherent and an appropriate (nothing worse than "PG-13" rated!) mnemonic, and to give a rousing reading of their OBAFGKM mnemonic poem for the class.

Oh Boy!! Asteroid Fragments are Gonna Kill Me...
--C. A.

One Big Ape Fights Giant Killer Moths
--B. A.

On Board A Fire Grew Keeping Me Trapped
--A. B.

Offshore Boaters Are Finding Giant Kelp Mounds
--R. B.

Only Baseless Accusations From Gluttonous Kings Make Royal Necks Sliced Clean
--D. B.

On Birthdays A Funny Grandma Karate-Chops a Mongoose
--L. B.

Oh Boy A Flying Giraffe King Married Len Tonight
--K. C.

Ooooooo Balls A Fiery Gnome Kicked Me Running Naked South of Chile
--T. D.

Oh Boy, Another Film Goes. Keeping Mediocre Ratings. Never Settle. Comedies!
--K. G.

Oh Brother A Flying Gorilla Killed Me
--R. H.

Over Board A Female Goat Kicked Me
--R. J.

On Board A Fairly Giant Killer Missile
--R. K.

Oh Be Afraid, Fat Grandmas Kill Monkeys
--C. L.

October Brings A Frightening Group! Kids Masked Like Turtle Ninjas
--J. L.

Oh Boy, Another Frustrated Girl Kicks Man
--D. M.

Oh Boy An F Grade Kills Me
--S. M.

Oh Bummer A Freaking Gorilla Killed My Lion, Theodore
--T. O.

Oh Banks Are Finally Giving Kind Money
--A. O.

Oh But Another Fine Guitarist Kiboshes My Loathsome Tabulating
--S. R.

Obviously, Bacon And Fat Grease Kills Men
--A. R.

Our Brother And Father Got Kinda Mad
--J. R.

Outrageous Builders Are Farming Giant Killer Monsters
--J. R.

Only Baby Animals Freak-out Good Kids' Mothers
--C. S.

Only Boys Attend Fighting Gangster Karate Movies
--A. S.

Only Bourne, A Fighter, Gets Killing Men
--K. S.

Oh Boy A Fat Girl Kissed Me
--A. T.

Oh Bob Accidentally Farts Gases Keeps Me Making Rare Noises
--Anonymous

Out Back A Fat Goat Kills Men
--Anonymous

Previous post: Astronomy in-class activity: OBAFGKM poetry slam instructions.

Astronomy in-class activity: OBAFGKM poetry slam (SLO)

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

Astronomy 210 In-class activity 14: OBAFGKM Poetry Slam

Students were instructed to use at least OBAFGKM, and/or part or all of the additional OBAFGKMRNSC or OBAFGKMLT extensions to individually write an original, coherent and an appropriate (nothing worse than "PG-13" rated!) mnemonic, and to give a rousing reading of their OBAFGKM mnemonic poem for the class.

Oh, Booze And Food Gets Kids Merry
--S. A.

Oh Boy, A Flying Gorilla Killed Ma!
--S. A.

Oh Buddy, Astronomy Frequently Gives Killer Migraines
--M. A.

Ouch! Bees Are Finally Gonna Kill Me.
--K. B.

Obama Bankrupts America; Fact. Gets KGB Membership.
--L. B.

Overweight Bats Are Fighting Gorillas in the Kona Mountains
--H. C.

Oo Bama Asked for Gorilla King Meat
--R. C.

Ogres Bite Americans For Giants Kill Monks
--H. C.

Obese Black women Are Frickin' Great Kitchen Moms
--B. D.

Obese Blue Aliens Fight Gassy Killer Medications
--J. E.

Oh Boy, Anyone Feeling Grumpy? Kinda? Maybe?
--M. F.

Only Betray A Friend if you're Going Krazy Man!! it's Really Not So Cool.
--L. G.

Only Bad Ass Fighters Get Killer Marks Like Tigers
--L. G.

Otter Babies Are Fluffy Giant Killer Machines
--A. G.

Oh Brother! A Fake Green Killer Mantaray!
--M. H.

Outnumbered British Admirals Fight Gallantly Killing Many Rebellious New Seamen
--M. H.

Open Before Another Fairy Gnome Kicks Me
--E. J.

Only Bewildered Astronauts Fear Ghenghis Khan's Machete
--B. J.

Octoberfest Beers Are Freakin Good @ Keeping Me Lightly Trashed
--J. J.

Octopus-Bears Are Freakin' Great Killing Machines
--K. J.

Our Bees Are Ferocious Ghosts! Killing Me...Like Tycho!
--C. K.

Only Bad-A**es For Governor, 'Kay Man?
--N. K.

On Blankets Are Flying Geese Kicking Mud
--B. L.

Oh Boy A Fat Guy Kicked Me
--J. M.

Obnoxious Bretheren Amplified Following Gallons of Killer Margaritas
--A. M.

One Big Astronomy Final. God Kill Me.
--P. M.

Obviously Bars Are For Gathering Kinky Moms
--T. M.

Octopuses Back Away From Gigantic Kayaks Mysteriously
--B. P.

Offering Beer At Family Gatherings Killed Mom
--L. P.

"Only Bears Are Fully Godless Killing Machines," Reports Newsman Stephen Colbert, Later Tonight.
--I. P.

Only Big Asteroids Force Giant Killer Monsoon
--J. R.

On Birthdays, A Fat Gut Kicks Me
--J. R.

Oh Be A Freakin' Guy, Kill Mice Lighting TNT!
--J. R.

Only Big Ass Funky Gorillas Kick Monkeys
--T. S.

Orangutans Bully All Furry Gorillas Kissing Monkeys
--R. S.

Oaring Back and Forth, Gallic King McFinnigan Returned North
--M. S.

Orange Belugas Assume Fred Gives Killer Makeovers
--D. S.

Outrageous Bitches Always Feel Good Killing Men
--T. S.

One Ballistic Angry Farmer Grew Killer Melons!!!
--M. S.

Oh Baby A Few Gushers Kindly More
--N. T.

Only Bob And Fred Go Kayaking Mondays
--N. T.

Only Bitchin' Acronyms Form Gnarly Knowledgeable Minds
My Krazy Glue Fixes All Broken Objects
--A. W.

Orange Bees Ally Free Giants Killing Mankind
--P. W.

Oak Branches Are Fairly Good at Killing Me
--M. Z.

Previous post: Astronomy in-class activity: OBAFGKM poetry slam instructions.

20091019

Astronomy midterm question: telling "moon-time"

Astronomy 210 Midterm 1, fall semester 2009
Cuesta College, San Luis Obispo, CA

Shown at right is an excerpt from a comic strip (Baby Blues, Rick Kirkman and Jerry Scott, King Features Syndicate, August 2, 2009). Given the phase of the moon shown here, discuss a plausible time at night for the events depicted in this comic strip, using a diagram showing the positions of the sun, moon, and Earth.

Solution and grading rubric:

p:
Correct. Identifies the phase as waxing gibbous, which is highest overhead at 9 PM (rising at 3 PM, and setting at 3 AM), using a diagram of the sun, moon, and Earth. May choose 9 PM, or anytime between sunset (6 PM) to 3 AM as being a plausible time for the events depicted in the comic strip.
r:
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. May include 3 PM in a range of plausible times, or diagram has minor inconsistencies/errors.
t:
Contains right ideas, but discussion is unclear/incomplete or contains major errors. Problems with either diagram, phase, or time.
v:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Problems with diagram, phase, and time.
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: 18 students
r: 2 students
t: 6 students
v: 12 students
x: 1 student
y: 2 students
z: 1 student

A sample "p" response (from student 1022), with a plausible range of times at night:

Another sample "p" response (from student ), with one chosen plausible time at night:

A sample "r" response (from student ), with daylight hours (3 PM-6 PM) included in the range of plausible times at night:

A sample "t" response (from student 5413), with the correct phase and a plausible time at night, but with a problematic diagram:

20091018

Astronomy midterm question: midnight Venus?

Astronomy 210 Midterm 1, fall semester 2009
Cuesta College, San Luis Obispo, CA

Consider the following excerpt regarding viewing Venus near midnight:

"When [Harry, Ron, Hermione] reached the top of the Astronomy Tower at eleven o'clock they found a perfect night for stargazing, cloudless and still... They entered the precise positions of the stars and planets they were observing... Half an hour passed, then an hour... Harry put his eye...to his telescope and refocused it, now examining Venus."
--J. K. Rowling, Harry Potter and the Order of the Phoenix, Scholastic (2003), pp. 718-719.

Discuss whether this is plausible or implausible. Support your answer using a diagram showing the positions of the sun, Venus, and Earth.

Solution and grading rubric:

p:
Correct. Discusses the implausibility of this scenario by drawing a diagram with Venus' orbit closer in to the sun than Earth's orbit, making it not possible for midnight observer (assumed to be at/near the equator) to observe Venus anywhere in its inner orbit.
r:
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Draws Venus in a geocentric orbit (and along or near the sun-Earth line) and argues implausibility based on this model (which is incorrect, but does reproduce the relative maximum possible angular separation between the sun and Venus).
t:
Contains right ideas, but discussion is unclear/incomplete or contains major errors. Argues plausibility based on a problematic heliocentric diagram, with Venus' orbit larger than Earth's orbit. Or argues implausibility based on a correct heliocentric diagram, with Venus' orbit closer in to the sun than Earth's orbit).
v:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. May discuss evening/morning star nature of Venus, elliptical orbital shapes, prograde/retrograde motion, phases, etc.
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: 18 students
r: 2 students
t: 6 students
v: 12 students
x: 1 student
y: 2 students
z: 1 student

A sample "p" response (from student 2416):

A sample "t" response (from student 5474), with Venus' heliocentric orbit larger than Earth's:

A sample "y" response (from student 2662), given credit for effort rather than merit:

20091017

Astronomy midterm question: radio telescope locations

Astronomy 210 Midterm 1, Fall Semester 2009
Cuesta College, San Luis Obispo, CA

[20 points.] Decide whether a proposed radio telescope should be placed on the ground or in outer space in order to be most cost-effective and be able to most efficiently gather astronomical data. Explain the reasoning behind your decision, in terms of relevant criteria discussed in this class.

Solution and grading rubric:

p = 20/20:
Correct. In general, the atmosphere is relatively transparent to radio waves, such that a ground-based telescope would be cheaper and just as effective as a space-based radio telescope. May argue for high-altitude or space-based radio telescopes for specific wavelengths that the atmosphere is relatively opaque for (e.g., FM/AM).
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. Does not specifically discuss the relative transparency of Earth's atmosphere to radio waves, but only in general terms such as disruption, inteference, distortion.
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.
y = 2/20:
Irrelevant discussion/effectively blank.
z = 0/20:
Blank.

Grading distribution:
Section 70160
p: 37 students
r: 0 students
t: 5 students
v: 0 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 7144), using toys made of solid gold as an analogy:

Another "p" response sample (from student 6363), narrowing the discussion of radio waves to the FM/AM band:

Yet another "p" response (from student 1022) discussing the criteria posed by the different types of radio waves:

20091016

Astronomy midterm question: telling "Moon-time"

Astronomy 210 Midterm 1, Fall Semester 2009
Cuesta College, San Luis Obispo, CA

[20 points.] Shown at right is an excerpt from a comic strip (Wizard of Id, Brant Parker and Johnny Hart, Creators Syndicate, June 28, 2009). Given the phase of the moon shown here, discuss a plausible time at night for the events depicted in this comic strip, using a diagram showing the positions of the sun, moon, and Earth.

Solution and grading rubric:

p = 20/20:
Correct. Identifies the phase as waning crescent, which is highest overhead at 9 AM (rising at 3 AM, and setting at 3 PM), using a diagram of the sun, moon, and Earth. May choose anytime between 3 AM to 6 AM (sunrise) as being a plausible time at night for the events depicted in the comic strip.
r = 16/20:
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. May include 9 AM or any time after sunrise, or diagram has minor inconsistencies/errors.
t = 12/20:
Contains right ideas, but discussion is unclear/incomplete or contains major errors. Problems with either diagram, phase, or time.
v = 8/20:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Problems with diagram, phase, and time.
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 70158
p: 15 students
r: 13 students
t: 7 students
v: 19 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 4614):

A sample "r" response (from 1623), who at least finds it strange that it is apparently dark outside:

Astronomy midterm question: ideal/non-ideal viewing conditions

Astronomy 210 Midterm 1, Fall Semester 2009
Cuesta College, San Luis Obispo, CA

[20 points.] Consider the following excerpt regarding viewing stars and planets at night:

"When [Harry, Ron, Hermione] reached the top of the Astronomy Tower at eleven o'clock they found a perfect night for stargazing, cloudless and still. The grounds were bathed in silvery moonlight... Each of them set up his or her telescope and...entered the precise positions of the stars and planets they were observing..."
--J. K. Rowling, Harry Potter and the Order of the Phoenix, Scholastic, New York, NY, 2003, pp. 718-719.

Discuss both the ideal and non-ideal conditions that would have affected telescopic observations on that night. Support your answer using factors that relate to the three telescope powers.

Solution and grading rubric:

p = 20/20:
Correct. Ideal: lack of atmospheric turbulence means that resolving power is not adversely affected. Non-ideal: moonlight will adversely affect the light-gathering power to image fainter stars.
r = 16/20:
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Discusses both ideal and non-ideal factors, but one citation from excerpt is problematic; or most generally discusses all factors that may affect viewing, but does not specifically apply it to the excerpt.
t = 12/20:
Contains right ideas, but discussion is unclear/incomplete or contains major errors. Correctly discusses only one of the ideal/non-ideal conditions specified in the excerpt.
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.
y = 2/20:
Irrelevant discussion/effectively blank.
z = 0/20:
Blank.

Grading distribution:
Section 70158
p: 22 students
r: 10 students
t: 20 students
v: 2 students
x: 0 students
y: 0 students
z: 0 students

A sample "p" response (from student 2522):

A sample "r" response (from student 7392), neglecting to address the light-pollution caused by moonlight, but also citing additional details from the book not specifically included in the above excerpt:

Astronomy midterm question: low west sunset Venus?

Astronomy 210 Midterm 1, fall semester 2009
Cuesta College, San Luis Obispo, CA

Consider the following excerpt regarding viewing Venus just after sunset:

"The stars were just now appearing, but to the west, a single point of light glowed brighter than any other. Langdon smiled when he saw it. It was Venus."
--Dan Brown, The Da Vinci Code: A Novel, Random House, New York, NY, 2003, p. 589.

Discuss whether this is plausible or implausible. Support your answer using a diagram showing the positions of the sun, Venus, and Earth.

Solution and grading rubric:

p = 20/20:
Correct. Discusses the plausibility of this scenario by drawing a diagram with Venus' orbit closer in to the sun than Earth's orbit, making it possible for an observer at sunset to observe Venus low on the west horizon.
r = 16/20:
Nearly correct (explanation weak, unclear or only nearly complete); includes extraneous/tangential information; or has minor errors. Draws Venus in the correct position in its orbit relative to Earth such that it would be seen just after sunset, but concludes that this would be implausible.
t = 12/20:
Contains right ideas, but discussion is unclear/incomplete or contains major errors. Argues plausibility or implausibility based on drawing Venus in its orbit relative to Earth such that it would be visible in the east horizon at sunrise, or is transiting the sun.
v = 8/20:
Limited relevant discussion of supporting evidence of at least some merit, but in an inconsistent or unclear manner. Draws a problematic diagram with Venus' orbit larger than Earth's orbit, or in a geocentric orbit around Earth.
x = 4/20:
Implementation/application of ideas, but credit given for effort rather than merit. Incomplete/inconclusive diagram, or argument based on retrograde/prograde motion.
y = 2/20:
Irrelevant discussion/effectively blank.
z = 0/20:
Blank.

Grading distribution:
Section 70158
p: 17 students
r: 5 students
t: 16 students
v: 11 students
x: 3 students
y: 2 students
z: 0 students

A sample "p" response (from student 1234):

A sample "r" response (from student 2388), with an incorrect conclusion, despite a correct diagram:

A sample "t" response (from student 7873), depicting Venus low in east horizon at sunrise:

A sample "v" response (from student 1781), using a geocentric model with phase/timing/horizon inconsistencies:

Physics midterm problem: constant speed block down ramp

Physics 205A Midterm 1, Fall Semester 2009
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Comprehensive Problem 4.112

[20 points.] A Physics 205A student wants a 20 kg box to slide with constant speed down a ramp that is inclined 10° from the horizontal. The coefficient of kinetic friction between the ramp and box is 0.40. What direction (up along the ramp, or down along the ramp) and magnitude force should the student exert on the box such that it slides down the ramp with constant speed? Assume that the box has already been unstuck. Show your work and explain your reasoning.

Solution and grading rubric:

p = 20/20:
Correct. Resolves weight into w_x and w_y components (parallel and perpendicular to ramp, respectively). Then applies Newton's first law along the (tilted) y-direction to find normal force of ramp on box, and thus f_k = mu_k*N (pointing up along the ramp). Since f_k up along the ramp is larger than w_x down along the ramp, F_applied needs to be the difference between their magnitudes f_k - w_x.
r = 16/20:
Nearly correct, but includes minor math errors. Typically uses N = w = m*g or N = w_y = m*g/cos(10 degrees) instead of N = w_y = m*g*cos(degrees); or sets F_app = f_k only, neglecting w_x component, otherwise methodical application of Newton's first law along y- and x- direciton. May also have sines and cosines switched, calculator was used in radians mode, or spurious force/component added back in.
t = 12/20:
Nearly correct, but approach has conceptual errors, and/or major/compounded math errors. Some attempt at resolving w into components on a substantive free-body diagram, and/or methodical application of Newton's first law along (tilted) y- and x- directions. May have two errors/omissions of those described in (r).
v = 8/20:
Implementation of right ideas, but in an inconsistent, incomplete, or unorganized manner. Serious attempt at free-body diagram and application of Newton's laws.
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:
Sections 70854, 70855, 72177
p: 12 students
r: 14 students
t: 12 students
v: 26 students
x: 1 student
y: 0 students
z: 0 students

A sample of a "p" response (from student 1717):

Another sample of a "p" response (from student 7895):

A sample of an "r" response (from student 2022), where the x- and y- components of weight were switched:

20091015

Physics midterm problem: jumping frog

Physics 205A Midterm 1, fall semester 2009
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 3.55(b)

[20 points.] A frog jumps at an angle of 40° from the horizontal, and lands back on the level ground 0.87 s later, a distance of 4.4 m away. Solve for the x- and y-components of its initial velocity. Show your work and explain your reasoning.

Solution and grading rubric:

p = 20/20:
Correct. Solves for average horizontal speed from given horizontal displacement and elapsed time, this must also be the initial horizontal velocity component v_ix. Then can use the initial trajectory angle to solve for v_iy = v_ix·tan(40°). Or can use half of flight time, and v_fy = 0 at top of trajectory to find v_iy .
r = 16/20:
Nearly correct, but includes minor math errors. May have shifted a decimal place, or used tan(40°) = adjacent/opposite, or apparent miscalculation of otherwise correct equations.
t = 12/20:
Nearly correct, but approach has conceptual errors, and/or major/compounded math errors. At least has v_ix = ∆x/∆t. Garbles attempt at using kinematics to find v_iy (typically using 0.87 s as the time to travel to its highest height).
v = 8/20:
Implementation of right ideas, but in an inconsistent, incomplete, or unorganized manner. Still has a methodical approach based on kinematics and/or trigonometry. May claim that ∆x/∆t is the magnitude of the initial velocity vector, which is then broken into v_ix and v_iy components using cos(40°) and sin(40°).
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:
Sections 70854, 70855, 72177
p: 26 students
r: 9 students
t: 9 students
v: 9 students
x: 10 students
y: 2 students
z: 0 students

A sample of a "p" response, using the time of flight and initial velocity vector angle to solve for the magnitude of the initial velocity vector, which is then broken into x- and y- components (from student 2323):

Another "p" response, using the time of flight and the horizontal range to solve for the x-component of the initial velocity vector, and together with the initial velocity vector direction is used to find the y-component of the initial velocity vector (from student 6405):

An "r" response, but with the entire flight time used to find the y-component of the initial velocity vector (from student 1251):

Another "r" response, with a misapplication of the tangent function (from student 2051):

A sample of a "v" response, where the x-component of the initial velocity vector is used as the magnitude of the initial velocity vector (from student 9685):

20091014

Astronomy current events question: x-rays from Milky Way center

Astronomy.com editors, "New Vista of Milky Way Center Unveiled," September 23, 2009
http://www.astronomy.com/asy/default.aspx?c=a&id=8651

What properties of x-rays make it possible for the NASA Chandra X-ray Observatory to study the center of the Milky Way? Circle your answer below.
(A) Not blocked by interstellar gas and dust.
(B) Can escape from the central supermassive black hole.
(C) Energetic enough to disrupt ground-based instruments.
(D) Not detectable anywhere on Earth.
(E) Readily passes through the Earth's atmosphere.

Correct answer: (A)

Student responses
Sections 70178, 70186, 70200
(A) : 14 students
(B) : 7 students
(C) : 2 students
(D) : 1 student
(E) : 6 students

20091013

Astronomy current events question: protoplanetary disk

Astronomy.com editors, "NASA's Spitzer Spots Clump of Swirling Planetary Material," September 24, 2009
http://www.astronomy.com/asy/default.aspx?c=a&id=8660

What have several scientists proposed as the cause of varying infrared light from a dusty disk around the star LRLL 31, detected by the NASA Spitzer Space Telescope? Circle your answer below.
(A) Outer layers of the star, as it becomes a planetary nebula.
(B) Protoplanets colliding.
(C) Neutron star pulsar beams
(D) A companion star or planet swirling material together.
(E) A black hole passing in front of the star.

Correct answer: (D)

Student responses
Sections 70178, 70186, 70200
(A) : 2 students
(B) : 1 student
(C) : 1 student
(D) : 24 students
(E) : 1 student

20091012

Astronomy current events question: evidence of lunar water

Astronomy.com editors, "Deep Impact and Other Spacecraft Find Clear Evidence of Water on Moon," September 24, 2009
http://www.astronomy.com/asy/default.aspx?c=a&id=8661

According to a University of Maryland researcher, what may be the source of surface water on the Moon detected by both the NASA Deep Impact mission and the India Chandrayaan-1 spacecraft? Circle your answer below.
(A) Solar wind reacting with Moon rocks.
(B) The large impact that originally formed the Moon.
(C) Contamination from the Apollo 11 mission.
(D) Russian rocket boosters.
(E) Water-bearing asteroids.

Correct answer: (A)

Student responses
Sections 70178, 70186, 70200
(A) : 24 students
(B) : 6 students
(C) : 3 students
(D) : 0 students
(E) : 13 students

20091002

Cuesta College North County campus star party

20091001319
http://www.flickr.com/photos/waiferx/3973094181/
Originally uploaded by Waifer X

Waxing gibbous moon, November 6, 2008, photographed with a Nokia e71 smartphone through a Orion 10" reflector at Cuesta College North County campus, Paso Robles, CA. Photo by Cuesta College Physical Sciences Division instructor Dr. Patrick M. Len.

091001-1110816
http://www.flickr.com/photos/waiferx/3973096639/
Originally uploaded by Waifer X

Cuesta College Astronomy 210L students from San Luis Obispo campus during a North County campus star party. These students made the inevitable In-n-Out Burger stop on the way back down the Cuesta grade. Photo by Cuesta College Physical Sciences Division instructor Dr. Patrick M. Len.

091001-1110817
http://www.flickr.com/photos/waiferx/3973098731/
Originally uploaded by Waifer X

Cuesta College Astronomy 210L students from San Luis Obispo campus pointing to the waxing gibbous moon during a North County campus star party. Photo by Cuesta College Physical Sciences Division instructor Dr. Patrick M. Len.

Sights seen:
Jupiter
Waxing gibbous moon

Astronomy current events question: Jupiter aurorae

Astronomy.com editors, "Ganymede's Magnetosphere Makes a Big Impression on Jupiter's Auroral Lights," September 17, 2009
http://www.astronomy.com/asy/default.aspx?c=a&id=8634

What did scientists from the University of Liege in Belgium detect on Jupiter using ultraviolet images from the Hubble Space Telescope? Circle your answer below.
(A) An impact from a colliding comet.
(B) New spiral weather patterns in its belt zones.
(C) The effect of the magnetic fields of its moons on its auroral bright spots.
(D) A newly discovered bright red spot.
(E) Traces of organic compounds associated with life on Earth.

Correct answer: (C).

Student responses
Sections 70178, 70186, 70200
(A) : 3 students
(B) : 3 students
(C) : 46 students
(D) : 6 students
(E) : 5 students

20091001

Astronomy current events question: D1 Herculis and general relativity

Robert Naeye, "Stellar Mystery Solved, Einstein Safe," September 16, 2009
http://www.skyandtelescope.com/news/59467082.html

According to researchers at Villanova University, why are the star orbits of the binary system D1 Herculis not obeying Einstein's general theory of relativity? Circle your answer below.
(A) Gravity from a previously undetected third star.
(B) The rotation axes of the stars are tilted over on their sides.
(C) Dense Earth-like planets orbiting very close in.
(D) The stars pass directly in front of each other, as seen from Earth.
(E) Matter is slowly being transferred from one star to the other.

Correct answer: (B).

Student responses
Sections 70178, 70186, 70200
(A) : 12 students
(B) : 35 students
(C) : 4 students
(D) : 6 students
(E) : 6 students