Astronomy current events question: gravity maps of the moon

Astronomy 210L, fall semester 2013
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!)

Davide Castelvecchi, "Gravity Maps Reveal Why the Moon's Far Side Is Covered with Craters," November 7, 2013
http://www.nature.com/news/gravity-maps-reveal-why-the-dark-side-of-the-moon-is-covered-in-craters-1.14106

Gravity maps produced by NASA’s Gravity Recovery and Interior Laboratory (GRAIL) spacecraft may explain why the near side of the moon:
(A) always faces towards Earth.
(B) does not produce tides as large as theoretically predicted.
(C) may harbor ice trapped in shadowed craters.
(D) is more radioactive.
(E) has large, shallow impact basins.

Correct answer: (E)

Student responses
Sections 70178, 70186, 70200
(A) : 1 student
(B) : 5 students
(C) : 2 students
(D) : 1 student
(E) : 49 students

Astronomy current events question: galaxy PGC 6240 shells

Astronomy 210L, fall semester 2013
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!)

Richard Hook, "Soft Shells and Strange Star Clusters," October 10, 2013
http://spacetelescope.org/news/heic1318/

Hubble Space Telescope images of the uneven structure and __________ of elliptical galaxy PGC 6240 indicate that it may be the result of a merger.
(A) dark matter and dark energy imbalance.
(B) different globular cluster ages.
(C) lack of spiral arms.
(D) red and orange colors.
(E) type II supernova activity.

Correct answer: (B)

Student responses
Sections 70178, 70186, 70200
(A) : 3 students
(B) : 47 students
(C) : 2 students
(D) : 0 students
(E) : 4 students

Astronomy current events question: gases flowing through quasar disks

Astronomy 210L, fall semester 2013
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!)

George Dvorsky, "This Quasar Should Not Exist--and Yet It Does," November 8, 2013
http://io9.com/this-quasar-should-not-exist-and-yet-it-does-1460860209

Canadian astronomers detected gas flowing directly into a black hole through its surrounding disk by looking at:
(A) Doppler-shifted light.
(B) time dilation.
(C) ejected jets.
(D) spacetime distortions.
(E) sudden increases in gravity.

Correct answer: (A)

Student responses
Sections 70178, 70186, 70200
(A) : 41 students
(B) : 2 students
(C) : 5 students
(D) : 0 students
(E) : 9 students

Physics quiz question: Hobble Creek Lodge human slingshot

Physics 205A Quiz 6, fall semester 2013
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e Problem 10.57

"Devinsupertramp Roadtrip!!! Behind the Scenes"
devinsupertramp
youtu.be/NzFo9N2DOYQ

A 70 kg person is attached to a bungee cord catapult[*] that can be approximated as a horizontal mass-spring system. The bungee cord is stretched 23 m from equilibrium, and when released, the person undergoes simple harmonic motion with a period of 4.0 s. Neglect friction and drag. The spring constant of the bungee cord is:
(A) 30 N/m.
(B) 60 N/m.
(C) 110 N/m.
(D) 170 N/m.

[*] Hobble Creek Lodge, 693 Hobble Creek Canyon Road, Springville, UT 84663.

Correct answer (highlight to unhide): (D)

The period T of a mass m attached to a spring with spring constant k is given by:

T = 2·π·√(m/k),

such that the spring constant k will be:

k = m·(2·π/T)² = (70 kg)·(2·π/(4.0 s))² = 172.718077 kg/s²,

or as expressed in more conventional units to two significant figures, the spring constant is 170 (kg·m/s²)·(1/m) = 170 N/m.

(Response (A) is m·g/A, where A = 23 m is the amplitude of the resulting idealized simple harmonic motion; response (B) is 2·m·g/A; and response (C) is m·(2·π/T).)

Sections 70854, 70855, 73320
Exam code: quiz06wR3k
(A) : 9 students
(B) : 10 students
(C) : 8 students
(D) : 37 students

Success level: 59%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.70

Physics quiz question: Miley Cyrus' "Wrecking Ball"

Physics 205A Quiz 6, fall semester 2013
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e Conceptual Question 10.4

Miley Cyrus, "Wrecking Ball"
Terry Richardson (director)
Vevo, September 9, 2013

In a recent music video[*], pop singer Miley Cyrus sits on a (fake) demolition wrecking ball, together approximated as a 120 kg point mass hanging from a steel cable. While stationary, the steel cable stretches by 1.2 mm when 120 kg is hanging from it. If 240 kg were suspended from a steel cable of the same length with twice the radius, then it would stretch by __________ 1.2 mm.
(A) less than.
(B) exactly.
(C) more than.
(D) (Not enough information is given.)

[*] Don't bother watching it. Also the chain in the video is simplified here as a uniform cable.

Correct answer (highlight to unhide): (A)

Hooke's law for the thin and thick cables are given by:

(F_thin/A_thin) = Y·(∆L_thin/L),
(F_thick/A_thick) = Y·(∆L_thick/L),

where the Young's modulus Y and the original, unstretched length L are the same for the thin and thick cables (being both made of steel). The thick cable has twice the load of the thin cable:

F_thick = 2·F_thin.

The radii and thus the cross-sectional areas of the thin and the thick cables are also different:

A_thin = π·r_thin²,
A_thick = π·r_thick².

The thick cable has a radius twice that of the thin cable (r_thick = 2·r_thin), which will give it a cross-sectional area of four times that of the thin cable:

A_thick = π·r_thick² = π·(2·r_thin)² = 4·π·r_thin² = 4·A_thin.

Then setting the ratio of Y/L for the thin and thick cables equal to each other:

Y/L = Y/L,

F_thin/(A_thin·∆L_thin) = F_thick/(A_thick·∆L_thick),

and substituting in F_thick = 2·F_thin and A_thick = 4·A_thin:

F_thin/(A_thin·∆L_thin) = 2·F_thin/(4·A_thin·∆L_thick),

1/∆L_thin = 1/(2·∆L_thick),

thus:

∆L_thick = (1/2)·∆L_thin,

such that the thick cable will stretch less than the thin cable.

Sections 70854, 70855, 73320
Exam code: quiz06wR3k
(A) : 12 students
(B) : 32 students
(C) : 20 students
(D) : 0 students

Success level: 19%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.08

Physics quiz question: making wavelength increase?

Physics 205A Quiz 6, fall semester 2013
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e Multiple-Choice Questions 11.5, 11.6

A steel cable 10.0 m long is pulled by a certain amount of tension. __________ of the steel cable would increase the wavelength of waves along the steel cable.
(A) Using a longer length.
(B) Decreasing the tension.
(C) (Either of the above choices.)
(D) (Neither of the above choices.)

Correct answer (highlight to unhide): (D)

The speed v of transverse waves along strings depends on the tension F and the linear mass density (mass per unit length) (m/L):

v = √(F/(m/L)).

Also the wavelength λ is the parameter that depends on the speed v and source frequency f, which can be varied independently of each other:

λ = v/f.

Using a longer length of this steel cable (with all other parameters fixed) would not affect the speed; while the length would get longer, the mass would proportionally increase as well, leaving the ratio (m/L) = (mass/length) unchanged.

Decreasing the tension F of the steel cable would decrease the speed v, and this would decrease the wavelength λ. Thus neither using a longer length of steel cable nor decreasing the tension of the steel cable would result in increasing the wavelength.

Sections 70854, 70855, 73320
Exam code: quiz06wR3k
(A) : 22 students
(B) : 27 students
(C) : 5 students
(D) : 9 students

Success level: 14%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.23

Physics quiz question: swaying electrical transmission lines

Physics 205A Quiz 6, fall semester 2013
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Conceptual Question 11.4, Multiple-Choice Question 11.5

"Swaying Power Lines.mpg"
lmwilliams100
youtu.be/US6iayPoBdM

An electrical transmission line in Northeast Arkansas covered with ice[*] sways back and forth at a fundamental frequency of 0.80 Hz, hanging from utility poles[**] with a spacing of 38 m. If the transmission line was no longer covered with ice (and assuming that the tension and length are relatively unchanged) the fundamental frequency would be __________ 0.80 Hz.
(A) lower than.
(B) equal to.
(C) higher than.
(D) (Not enough information is given.)

[*] youtu.be/US6iayPoBdM.
[**] wki.pe/Utility_pole.

Correct answer (highlight to unhide): (C)

The fundamental frequency f₁ of a string of length L is given by:

f₁ = v/(2·L),

where the speed v of transverse waves along the string depends on the tension F and the linear mass density (mass per unit length) (m/L):

v = sqrt(F/(m/L)).

If the transmission line was no longer covered by ice, and given that the tension and the length would be relatively unchanged, then there will be a decrease in mass per length of transmission line, such that (m/L) decreases, increasing v, and thus increasing the fundamental frequency f₁ that the transmission lines will sway back and forth.

Sections 70854, 70855, 73320
Exam code: quiz06wR3k
(A) : 7 students
(B) : 24 students
(C) : 33 students
(D) : 0 students

Success level: 52%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.51

Physics quiz archive: simple harmonic motion, waves

Physics 205A Quiz 6, fall semester 2013
Cuesta College, San Luis Obispo, CA
Sections 70854, 70855, 73320, version 1
Exam code: quiz06wR3k



Sections 70854, 70855, 73320 results

0- 6 :	* [low = 3]
7-12 :	**************
13-18 :	********************************** [mean = 15.5 +/- 5.2]
19-24 :	**********
25-30 :	** [high = 27]

Physics quiz question: rotational inertia of Solowheel wheel

Physics 205A Quiz 5, fall semester 2013
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 8.2

"Riding the Solowheel to work - every days obstacle course"
SoloWheela
youtu.be/w2PATMZFEJo

A Solowheel motorized unicycle[*] rolls without slipping on a horizontal road with a wheel that can be approximated as a solid disk of radius 0.21 m and mass 5.0 kg. The rotational inertia of the Solowheel wheel is:
(A) 0.011 kg·m².
(B) 0.11 kg·m².
(C) 0.22 kg·m².
(D) 2.2 kg·m².

(Given: I_disk = (1/2)·M·R².)

[*] solowheel.com/solowheel-specs/.

Correct answer (highlight to unhide): (B)

Since the Solowheel wheel can be approximated as a solid disk,

I = (1/2)·m·r² = (1/2)·(5.0 kg)·(0.21 m)² = 0.11025 kg·m²,

or to two significant figures, the rotational inertia is 0.11 kg·m².

(Response (A) is (5.0 kg)·(0.21 m)/(100 kg); response (C) is the rotational inertia (5.0 kg)·(0.21 m)² for a ring (instead of a solid disk); response (D) is (1/2)·(100 kg)·(0.21 m)².)

Sections 70854, 70855, 73320
Exam code: quiz05LuF7
(A) : 6 students
(B) : 32 students
(C) : 10 students
(D) : 13 students

Success level: 52%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.39

Physics quiz question: lever arm of applied force

Physics 205A Quiz 5, fall semester 2013
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problems 8.19, 8.35

A horizontal force is applied to the middle of a square uniform object to keep it stationary. 
The square object is 0.50 m on each side, mounted on a 
pivot at one corner. (Calculate all torques with respect to 
the pivot.) The r_⊥ lever arm for the applied force is:
(A) 0.25 m.
(B) 0.35 m.
(C) 0.50 m.
(D) 0.56 m.

Correct answer (highlight to unhide): (A)

First, a line of force is extended along the force vector. The perpendicular lever arm for this force is drawn such that it starts at the pivot point, and must end intersecting the line of force perpendicularly. Here, the line of force extends through the midpoint of the square object. The perpendicular lever arm then starts from the pivot point, along the side of the square, and ends at the line of force, halfway along the side of the square. Thus the perpendicular lever arm is one-half of the side of the square, or 0.25 m.

(Response (B) is the diagonal distance from a corner to the center of the square; response (C) is the side of the square; and response (D) is the diagonal distance from one corner of the square to the opposite corner.)

Sections 70854, 70855, 73320
Exam code: quiz05LuF7
(A) : 35 students
(B) : 5 students
(C) : 14 students
(D) : 7 students

Success level: 57%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.18

Physics quiz question: air pressure in Krubera Cave

Physics 205A Quiz 5, fall semester 2013
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 9.19(a)

The entrance to Krubera Cave[*] in the Abkhazia region of Georgia is 2,256 m above sea level. It is the deepest known cave, explored to a depth of 2,197 m from its entrance. Assuming that the gravitational constant g and the density of air do not vary with elevation, the air pressure at the deepest explored point in Krubera Cave is __________ the air pressure at sea level.
(A) less than.
(B) equal to.
(C) greater than.
(D) (Not enough information is given.)

[*] Source: wki.pe/Krubera_Cave.

Correct answer (highlight to unhide): (A)

For static fluids, the energy density relation between pressure and changes in elevation is given by:

0 = ∆P + ρ·g·∆y,

0 = (P_{deepest point} – P_{sea level}) + ρ·g·(y_{deepest point} – y_{sea level}),

where the air pressure at sea level is 101.3 kPa = 1.013×10⁵ Pa, such that:

P_{deepest point} = P_{sea level} – ρ·g·(y_{deepest point} – y_{sea level}).

Since the entrance to Krubera Cave is 2,256 m above sea level, and the deepest explored point is 2,197 m below the entrance, the deepest explored point in Krubera Cave is 2,256 m – 2,197 m = 59 m above sea level, making the quantity (y_{deepest point} – y_{sea level}) positive, and thus the pressure in the deepest explored point in Krubera Cave is slightly less than the air pressure at sea level (with the above assumptions).

Sections 70854, 70855, 73320
Exam code: quiz05LuF7
(A) : 28 students
(B) : 6 students
(C) : 27 students
(D) : 0 students

Success level: 46%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.43

Physics quiz question: raising the sunken Mighty Servant 3

Physics 205A Quiz 5, fall semester 2013
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problems 9.27, 9.31

"Mighty Servant 3 carrying her last cargo, the semi-submersible drilling rig GSF Aleutian Key"
(Anonymous)
wki.pe/File:20061204_MightyServant3_JUSTbefore.JPG

In December 6, 2006 the ship Mighty Servant 3 accidentally sank, resting fully submerged on the ocean floor.[*] (No lives were lost in this incident.) The Mighty Servant 3 was later raised by filling its water-filled compartments with air. Up until the point where it just began to rise off of the ocean floor, its weight __________, while the buoyant force on it __________ in magnitude.
(A) decreased; decreased.
(B) decreased, remained constant.
(C) decreased; increased.
(D) increased; decreased.
(E) increased; remained constant.
(F) increased; increased.

[*] cargolaw.com/2006nightmare_mightyserve3.html.

Correct answer (highlight to unhide): (B)

The magnitude of the buoyant force is given by:

F_B = ρ_fluid·g·(Volume submerged),

where the density ρ is of the surrounding fluid (seawater) and the gravitational constant g = 9.80 m/s². The volume of sea water displaced by the ship, while still completely submerged, does not change, and thus the buoyant force on it still has the same magnitude while it is filling with air. However, since air is replacing the seawater in its compartments, the weight of the ship decreases.

Sections 70854, 70855, 73320
Exam code: quiz05LuF7
(A) : 5 students
(B) : 31 students
(C) : 23 students
(D) : 1 student
(E) : 1 student
(F) : 0 students

Success level: 51%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.50

Physics quiz question: cross-sectional area of pipe

Physics 205A Quiz 5, fall semester 2013
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 9.43(b)

Water at point [1] flows with a speed of 
3.0 m/s and a volume flow rate of 0.40 m³/s. The pipe at point [2] 
is four times the cross-sectional area of point [1]. Assume ideal 
fluid flow. The cross-sectional area of the pipe at point [1] is:
(A) 0.13 m².
(B) 1.2 m².
(C) 4.5 m².
(D) 7.5 m².

Correct answer (highlight to unhide): (A)

The definition of volume flow rate is:

(∆V/∆t) = A·v,

where A is the cross-sectional area of the pipe, and v is the speed of the fluid at that same location, such that:

A = (∆V/∆t)/v = (0.40 m³/s)/(3.0 m/s) = 0.13333333... m²,

or to two significant figures, the cross-sectional area at point [1] is 0.13 m².

(Response (B) is (∆V/∆t)·v; response (C) is (1/2)·v²; response (D) is v/(∆V/∆t).)

Sections 70854, 70855, 73320
Exam code: quiz05LuF7
(A) : 34 students
(B) : 20 students
(C) : 4 students
(D) : 3 students

Success level: 69%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.40

Physics quiz archive: rotations, torque, pressure, buoyancy, fluid flow

Physics 205A Quiz 5, fall semester 2013
Cuesta College, San Luis Obispo, CA
Sections 70854, 70855, 73320, version 1
Exam code: quiz05LuF7



Sections 70854, 70855, 73320 results

0- 6 :
7-12 :	************ [low = 12]
13-18 :	*********************** [mean = 18.4 +/- 4.9]
19-24 :	**********************
25-30 :	**** [high = 30]

Online reading assignment: temperature

Physics 205A, fall semester 2013
Cuesta College, San Luis Obispo, CA

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 questions were asked on reading textbook chapters and previewing a presentation on temperature.

Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.

"All of the railroad track examples. My dad works for Union Pacific and talks about this stuff all the time."

"That one could economically benefit from pumping gas at a certain time of the day because temperature directly effects the volume of gasoline that flows into the tank."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.

"I don't think anything was too confusing. This section was straightforward. I will probably have questions when we start working on it in class and get into the material more."

"That tracks are built in order to accommodate fluctuating temperatures. I don't understand how the length of the track is determined such that it does not expand or contract too much for the train to continue on the tracks."

For solids, what does α (Greek lowercase letter "alpha") in the linear thermal expansion equation stand for, and what SI units does it have?

"The linear expansion coefficient, unitless."

"Linear expansion coefficient, K^-1."

"Coefficient of linear expansion; K^-1 or °C^-1."

Note the quantity (L/∆L) in for linear thermal expansion. What was this quantity called back in the context of elasticity?

"Elastic modulus."

"A fractional length change."

"Strain."

A square brass plate has a circular hole in its middle. How do each of the quantities change as the brass plate increases in temperature?
(Only correct responses shown.)

Width of the square plate: increases [73%]
Area of the square plate: increases [75%]
Diameter of the hole: increases [50%]
Area of the hole: increases [49%]

For solids, what is the mathematical relationship between the coefficient of volume expansion β and the coefficient of linear expansion α?

"α = (∆L)/L; β = (∆V)/V."

"They are both multiplied by ∆T."

"β = 3·α."

A tank contains a certain amount of gasoline at a cool temperature. How do each of the quantities change as the gasoline increases in temperature?
(Only correct responses shown.)

Mass of the gasoline: remains constant [79%]
Volume of the gasoline: increases [67%]
Density of the gasoline: decreases [62%]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"I'd like it if when we're doing practice problems in class, we discussed more about why we chose the equation we chose. Most of the time it's just a brief mention, if there's any mention at all, and it makes the material practically impossible to understand when applying it to quizzes. Solving the equation is the easy part; choosing an equation in the midst of all the millions of equations we have to know is the hard part." (Yes, exactly. I'll try to do more of this, and if the choice of which equation is not obvious in solving a problem, please feel free to ask!)

"Do railroad tracks that buckle have to be replaced? Or do they revert back to their original form when the temperature cools?" (Even if the tracks had expanded less than their elastic limit, then they may not necessarily straighten out again when cooler, as they are fastened down to the buried railroad ties (or sleepers) buried in the ground, which may not shift back to their original positions.)

"Can we please go over practice problems in class?" (I'll try to do some example problems for you in class, and as always allocate 10-15 minutes at the end of class so you can ask me questions while you start on the assigned homework problems.)

Online reading assignment: sound

Physics 205A, fall semester 2013
Cuesta College, San Luis Obispo, CA

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 questions were asked on reading textbook chapters and previewing a presentation on sound.

Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.

"The speed of sound in air depends on the absolute temperature and that sound travels faster through warmer air and slower through cooler air."

"When dealing with an asymmetrical pipe, standing waves are produced only at odd multiples of the fundamental frequency."

"The subwoofer shredding the phonebook!"

"The different species of animals have different ways of communicating with each other with low frequency sound waves or high frequency sound waves."

"I love finding out how musical instruments and other various everyday things work."

"The human ear is only responsive to sound waves in a limited range of frequencies. Most humans cannot hear sounds within the full range. Other organisms would not survive if they could only hear the range of frequencies we are able to hear."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.

"I'm confused about the pipe section. I don't really understand the effects of an open versus closed-ends on pipes."

"Resonant frequencies, due to the different types and when they are valid."

"Nothing."

"I found it confusing to detect a sound wave because even transverse waves that make a sound do not qualify as a sound wave."

For sound waves, what does the T for sound wave speeds stand for, and what SI units does it have?

"The T stands for the temperature which is in kelvins (K)."

"The 'T' stands for period and the SI units are Hz or s^-1."

FFor sound waves in air, classify each of these parameters are being "independent" (able to be changed without affecting other independent parameters), or "dependent" (will be changed when independent values are changed).
(Only correct responses shown.)

Amplitude A: independent [77%]
Wave velocity v : independent [67%]
Frequency f : independent [80%]
Wavelength λ : dependent [82%]

For sound waves in a tube, classify each of these parameters are being "independent" (able to be changed without affecting other independent parameters), or "dependent" (will be changed when independent values are changed).
(Only correct responses shown.)

Sound wave velocity v: independent [58%]
Tube length L: independent [66%]
Fundamental frequency f₁: dependent [56%]
Frequency f of sound "blown" into tube: independent [69%]

Select the standing sound waves that would resonate in the tubes below.
(Only correct responses shown.)

Tube open at both ends: all multiples of f₁ [42%]
Tube open at one end, and closed at the other end: only odd multiples of f₁ [75%]
Tube closed at both ends: all multiples of f₁ [62%]

What musical instrument(s) do you play? List none, or as many as applicable.

"None." [19 responses]

"Guitar." [9 responses]

"Piano." [14 responses]

"Air guitar."

"Singing." [5 responses]

"Flute." [4 responses]

"Does a triangle count?"

"Saxophone." [2 responses]

"Clarinet." [4 responses]

"Harmonica." [2 responses]

"Ukulele."

"Piccolo"

"Mandolin."

"Trumpet." [4 responses]

"Trombone." [2 responses]

"Drums." [2 responses]

"Cajón [Peruvian percussion box]."

"Banjo."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"For wave propagation, we were saying that λ = v/f, where wavelength is the only one dependent in that relationship. Does the standing sound waves equation mean that frequency is dependent on wavelength, or does it only apply to the math?" (The fundamental frequency for sound waves in a tube is dependent on the length of the tube, and the speed of sound waves in air. However, the frequency of sound waves that go into the tube can be set independently, but will only produce resonance in the tube if it matches the fundamental frequency. Learning to play a woodwind or brass instrument is a trial-and-error process of varying your sound wave frequency (produced by a reed and/or your lips) to match the instrument's fundamental frequency.)

"For the upcoming midterm can you put additional problems from the textbook to practice in addition to the ones you give us in class?" (Well, most of the midterm study questions are similar questions from previous semesters' midterms.)

"What musical instrument(s) do you play?" (Piano, ukulele, and in grade school, the most played instrument in 20th century.)

Online reading assignment: the Milky Way (SLO campus)

Astronomy 210, fall semester 2013
Cuesta College, San Luis Obispo, CA

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 questions were asked on reading textbook chapters and previewing presentations on the Milky Way's shape, size and composition and spiral arm structure and formation.

Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.

"Dark matter is really cool. It's there but you cant see it. How is that not interesting?"

"I thought the whole chapter was interesting, I enjoyed learning about the galaxy we live in."

"Shapely's process of measuring and calibrating Cepheid variable stars. It took some serious intellect to figure out what he did. "

"How the arms of the Milky Way are formed, and the way the stars aren't going into the center but are just following a circle, but looks like an arm because they group up at certain points."

"The length of time it takes the sun to complete an orbit in the Milky Way. Interesting because you never think about the sun being the one to orbit something."

"I found it interesting that the mass holding the Milky Way together does not reflect light, absorb light, emit light, or interact with light in any way but the Milky Way looks full of light."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.

"Globular clusters and how they determine our location in and the size of our galaxy."

"What I found to be particularly confusing was gravity and orbits of the Milky Way. This was confusing to me just because it is hard to recognize the difference in the two motions on the slide which made it further more confusing for me."

"I'm confused as to why the Milky Way appears 'blue'--shouldn't it appear pink due to hydrogen and star formation?"

"The second presentation was a bit confusing to me. I don't understand what the Pimpstar™ rims are about and how that works."

In your experience, how much of the "Milky Way" (the band of faint stars across the celestial sphere) have you been able to see in the night sky?

As much as can be seen with the naked eye.	************** [14]
Not very much.	***************** [17]
Barely seen it.	********* [9]
(Never been able to see it.)	****** [6]
(Unsure/guessing/lost/help!)	[0]

Using the most powerful light-gathering telescopes in the darkest skies, up to how much of the stars in our entire galaxy can be observed from Earth?

1%.	********* [9]
5%.	****** [6]
10%.	*************** [15]
50%.	**** [4]
100%.	** [2]
(Unsure/guessing/lost/help!)	****** [6]

If you did not have access to a mirror while camping, what could you do to find out whether or not you're having a bad hair day?

"Simple, I would bust out my phone and use the front-facing camera app."

"I can usually feel the horribleness when I wake up."

"Use something reflective like a glass bottle or some type of shiny metal to fashion a crude mirror."

"Look into the reflection of your trusted camping spoon."

"I would know by rubbing my hand against my head. I would feel a clump of hair that is giving me my cow lick."

"My shadow."

"I have no idea. I wouldn't bother with it, I'm CAMPING! :)"

"See if wild animals run away from you. Or hit on a fellow camper and see how far you get."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"I enjoy your presentations. Even with the lowest grade of my life, I still find your class to be the most interesting."

I am totally gonna get me some of those Pimpstar™ rims!"

"That bike of yours is legen...wait for it...DARY!"

"I just saw the movie Ender's Game and in it they were traveling in space. They showed large and small dust particles and emission of hydrogen. But when they for to a planet that was near a yellow medium mass star it has some things shimmer the color yellow. Is that possible?" (No. But it's just a movie.)

"Is there a way to tell when our galaxy eats another galaxy?" (It's happening right now!)

Astronomy current events question: Square Kilometer Array

Astronomy 210L, fall semester 2013
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!)

Corinne Mosese, "Work Starts on the World’s Largest Radio Telescope," November 4, 2013
http://www.stfc.ac.uk/2925.aspx

Construction started on the Square Kilometer Array, which will become the world's largest radio telescope by:
(A) collecting static from cell phone towers.
(B) combining receivers in Australia and South Africa.
(C) using Earth's entire magnetic field.
(D) laying out a wire mesh at the south pole.
(E) using the moon as a passive radio reflector.

Correct answer: (B)

Student responses
Sections 70178, 70186, 70200
(A) : 0 students
(B) : 43 students
(C) : 9 students
(D) : 1 student
(E) : 5 students

Astronomy current events question: estimate of Earth-sized planets in habitable zones

Astronomy 210L, fall semester 2013
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!)

Erik Petigura, Andrew Howard, Geoff Marcy, and Steve Jefferson, "One in Five Stars Has Earth-sized Planet in Habitable Zone," November 4, 2013
http://www.keckobservatory.org/recent/entry/one_in_five_stars_has_earth_sized_planet_in_habitable_zone

As much as 20% of sun-like stars in the Milky Way may __________, based on statistical analysis of data from the Kepler Space Telescope.
(A) undergo type II supernova explosions.
(B) have Earth-sized planets.
(C) be extremely metal-rich.
(D) harbor carbon-based life.
(E) outlive the Milky Way itself.

Correct answer: (B)

Student responses
Sections 70178, 70186, 70200
(A) : 2 students
(B) : 53 students
(C) : 0 students
(D) : 1 student
(E) : 1 student

Astronomy current events question: Smith Cloud magnetic field

Astronomy 210L, fall semester 2013
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!)

Charles Blue, "Magnetic 'Force Field' Shields Giant Gas Cloud during Collision with Milky Way," October 31, 2013
https://public.nrao.edu/news/pressreleases/magnetic-force-field-shields-giant-gas-cloud/

The __________ deep inside the Smith Cloud detected by the Very Large Array and the Green Bank Telescope may explain how it is able to pass through the Milky Way intact.
(A) dark matter core.
(B) x-ray pulsar.
(C) molecular cloud.
(D) supermassive black hole.
(E) magnetic field.

Correct answer: (E)

Student responses
Sections 70178, 70186, 70200
(A) : 9 students
(B) : 0 students
(C) : 7 students
(D) : 0 students
(E) : 42 students

Online reading assignment: simple harmonic motion

Physics 205A, fall semester 2013
Cuesta College, San Luis Obispo, CA

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 questions were asked on reading textbook chapters and previewing a presentation on simple harmonic motion.

Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.

"It is interesting to me that mass doesn't seem to effect the simple pendulum period. I always thought that a greater mass would swing more slowly."

"I really enjoyed the textbook discussion of walking as being similar to a pendulum swinging. It's something that I've both never noticed or considered. I'm definitely gonna be paying attention to that for the next few days."

"The human slingshot in the presentation seemed pretty cool but other than that this section wasn't too intriguing."

"The pendulum, because 'The Pit and the Pendulum' is one of my favorite Edgar Allen Poe stories."

"I found it easy to understand when the book said that the word 'simple' in SHM means that the amplitude of the vibration is constant."

"That simple harmonic motion can be applied to uniform circular motion. The position and acceleration of a pin moving in a circular motion, in SHM can be found using sinusoidal functions."

"Nothing."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.

"I don't understand rationally why an object with a greater mass would not swing back-and-forth more slowly (unless it would only effect the period of time because of air resistance)."

"I got lost with analyzing simple harmonic motion with energy conservation."

"Nothing was too bad."

"I don't really understand the pendulum period equations. I understand how to solve using the equation, but I don't fully understand when to use which (the one focused on mass or the one focused on length). The GIF animations really help, but I think I need to read more about this in the book."

For simple harmonic motion of a mass on a spring, classify each of these parameters are being "independent" (able to be changed without affecting other independent parameters), or "dependent" (will be changed if (other) independent values are changed). Ignore friction/drag.
(Only correct responses shown.)

Spring constant k: independent [68%]
Mass m : independent [68%]
Amplitude A : independent [42%]
Period T : dependent [74%]

For simple harmonic motion of a simple pendulum (point mass on a string), classify each of these parameters are being "independent" (able to be changed without affecting other independent parameters), or "dependent" (will be changed if (other) independent values are changed). Ignore friction/drag.
(Only correct responses shown.)

String length L: independent [68%]
Mass m : independent [72%]
Amplitude A : independent [52%]
Period T : dependent [84%]

Why do the K and U graphs in Fig. 10.20 (p. 374) always have positive values?

"These values are always positive."

"Because negatives don't make sense in those values."

"Because you don't ever have negative energy."

"Because the mass and spring constant are positive numbers, and you could have a -x (displacement) depending on the direction but it is squared, making it a positive number. The velocity is also squared, making it a positive number as well."

"You either have some energy or none at all, there is no 'negative energy.'"

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"This course is pretty hard to grasp but I'm getting better and better at it."

"What is the restoring force for a mass-spring system?" (The force of the spring that pulls or pushes an object back to its equilibrium position.)

"I found the graph interpretations as well as differentiating between dependent and independent perimeters to be difficult. I could use an explanation on these to better understand the concept of harmonic motion." (Yes.)

"I'm scared for the midterm."

"Looking forward to your lecture on this. I normally feel pretty shaky going in, but you seem to always find a way to make the topic simple and understandable!"

"I'm really enjoying your class, I had a horrible teacher in high school and I was really nervous about taking this again, but it's one of my favorite classes! Thanks!"

Online reading assignment: the Milky Way (NC campus)

Astronomy 210, fall semester 2013
Cuesta College, San Luis Obispo, CA

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 questions were asked on reading textbook chapters and previewing presentations on the Milky Way's shape, size and composition and spiral arm structure and formation.

Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.

"That the Milky Way contains approximately 100–400 billion stars. And planets."

"I like the idea of dark matter. Not so much because of what we think it is, but because of the fact that we don't know. It's cool to think that there's still things out there that we just don't understand."

"Spiral galaxies are beautiful! The arms are cool to look at."

"The Milky Way and where we are located inside of it and what it consists of. This was interesting because seeing it in the night sky you can honestly look at it for hours, and it is good to know more things about it."

"That gas and dust is blocking the full view of the Milky Way because we can't really tell how big it is."

"I thought it was fascinating that our galaxy cannibalizes its brethren. Brutal."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.

"I didn't really understand the how and why of the Milky Way's spiral arms. Why does the Milky Way spiral outward?"

"How does dark matter hold the Milky Way together, but doesn't emit any type of light?"

"I didn't understand how distances to globular clusters are determined."

"It makes sense that gravity would have to be what's keeping the Milky Way together, but how can it be determined that it is from the dark matter in the galaxy and not another source."

"I don't understand how we find our location in reference to the Milky Way."

Using the most powerful light-gathering telescopes in the darkest skies, up to how much of the stars in our entire galaxy can be observed from Earth?

1%.	****** [6]
5%.	* [1]
10%.	*** [3]
50%.	**** [4]
100%.	******* [7]
(Unsure/guessing/lost/help!)	*** [3]

If you did not have access to a mirror while camping, what could you do to find out whether or not you're having a bad hair day?

"Ask someone."

"Find an area with still water so you can look at your reflection."

"Touch your head."

"I personally keep my hair short so I don't have to worry about that."

"I would just put a hat on--it's camping, it doesn't matter."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"I saw this Saturn with a license plate frame that said, "Touch my Saturn, I'll kick Uranus." I lol'ed."

"Class has been fun this semester ^ ^." (You're welcome.)

"I want a star party."

"What does the fox say?" (This. This is what the fox says.).

Astronomy current events question: waterless carbon-rich exoplanets

Astronomy 210L, fall semester 2013
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!)

Whitney Clavin, "Carbon Worlds May be Waterless, Finds NASA Study," October 25, 2013
http://www.jpl.nasa.gov/news/news.php?release=2013-308

NASA Jet Propulsion Laboratory scientists proposed that carbon-rich exoplanets would lack water, based on comparing computer models of __________ in our solar system.
(A) carbon-14 decay.
(B) planet evolution.
(C) the greenhouse effect.
(D) diamond formation rates.
(E) carbon-based life.

Correct answer: (B)

Student responses
Sections 70178, 70186
(A) : 5 students
(B) : 11 students
(C) : 0 students
(D) : 10 students
(E) : 14 students

Astronomy current events question: supernova candidate PSN J18032459+7013306

Astronomy 210L, fall semester 2013
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!)

Deborah Thompson, "Ten-year-old Canadian Boy Discovers a 600 Million Year-Old Supernova," November 1, 2013
http://www.rasc.ca/news/ten-year-old-canadian-boy-discovers-600-million-year-old-supernova

10-year-old Nathan Gray discovered supernova candidate PSN J18032459+7013306 from:
(A) listening to radio interference.
(B) deciphering a Mayan codex.
(C) a science fair project gamma-ray detector.
(D) scanning recent telescope images.
(E) a 100-year-old star chart.

Correct answer: (D)

Student responses
Sections 70178, 70186
(A) : 1 student
(B) : 0 students
(C) : 5 students
(D) : 34 students
(E) : 0 students

Astronomy current events question: Kepler-78b

Astronomy 210L, fall semester 2013
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!)

Irene Klotz, "Earth's Hellish 'Twin Sister' Discovered," October 30, 2013
http://news.discovery.com/space/alien-life-exoplanets/earths-hellish-twin-sister-discovered-131030.htm

Earth-sized exoplanet Kepler-78b's __________ indicate that it is covered with molten lava.
(A) close orbit to its star.
(B) lack of polar ice caps.
(C) strong greenhouse effect.
(D) massive iron core.
(E) lack of impact craters.

Correct answer: (A)

Student responses
Sections 70178, 70186
(A) : 28 students
(B) : 2 students
(C) : 1 student
(D) : 8 students
(E) : 1 student

Astronomy current events question: Large Underground Xenon dark-matter detector results

Astronomy 210L, fall semester 2013
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!)

Eugenie Samuel Reich, "No Sign of Dark Matter in Underground Experiment," October 30, 2013
http://www.nature.com/news/no-sign-of-dark-matter-in-underground-experiment-1.14057

The Large Underground Xenon (LUX) experiment has not yet detected anything, which is evidence that dark matter:
(A) has an extremely long radioactive half-life.
(B) completely decayed into dark energy.
(C) is weaker or less massive than expected.
(D) does not gravitationally interact with Earth's core.
(E) repels xenon atoms.

Correct answer: (C)

Student responses
Sections 70178, 70186
(A) : 4 students
(B) : 0 students
(C) : 30 students
(D) : 3 students
(E) : 2 students

Online reading assignment: waves

Physics 205A, fall semester 2013
Cuesta College, San Luis Obispo, CA

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 questions were asked on reading textbook chapters and previewing a presentation on waves.

Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.

"A wave has the ability to transmit energy in-between points but not the ability to transport any material between points."

"Standing waves are absolutely fascinating. It took me a little while to understand them, but it was definitely worth the effort. And on a side note those animated GIFs are crazy to watch, especially the last one."

"Well..the animated GIFs are cool but I'm not really understanding the concepts"

"I had no idea that whips actually break the sound barrier. I also found it interesting that the speed is directly proportional to the force [tension] and size [thickness] of the object."

"I really liked this section a lot. I felt very interesting in learning about all the different wave types and how they exist in the real world. The video on the Tacoma Narrows Bridge is crazy! Very interesting to watch and learn about. It is amazing to me that the bridge could be moved by the waves that much and not just break immediately."

"Nothing--it's all confusing."

"I found the guitar example very interesting, being a guitarist myself."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.

"I am not clear on what a standing wave is."

"Honestly, almost the entirety of this presentation confuses me."

"Aside from the book being a little cryptic at times and requiring re-reading (which is hardly new), there wasn't much that was confusing with this section."

"The equations on how they should be used was confusing to me. I'm not to sure when what equation is used for what."

"I found it confusing to discuss standing waves in terms of resonance. I don't fully understand this concept and would benefit from explanation in class."

A string of length 2.0 m has a certain linear mass density µ (Greek lower-case "mu") value of 0.0044 kg/m. If this string is cut in half, then its linear mass density µ will:

decrease.	*************** [15]
remain constant.	************** [14]
increase.	********* [9]
(Unsure/guessing/lost/help!)	***** [5]

For transverse waves on a string, classify each of these parameters are being "independent" (able to be changed without affecting other independent parameters), or "dependent" (will be changed when independent values are changed).
(Only correct responses shown.)

Amplitude A: independent [61%]
Wave velocity v : independent [64%]
Frequency f : independent [53%]
Wavelength λ : dependent [70%]

For transverse standing waves on a string, classify each of these parameters are being "independent" (able to be changed without affecting other independent parameters), or "dependent" (will be changed when independent values are changed).
(Only correct responses shown.)

Wave velocity v : independent [51%]
String length L : independent [72%]
Fundamental frequency f₁ : dependent [64%]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"For the transverse wave speed on a string, I don't see how the speed at which the wave travels is affected by the length of the string." (It's not.)

"Do we need to understand and remember the trigonometric equations for standing waves?" (What?!? No. But you do need to know how the standing wave parameters depend (or do not depend) on each other.)

"Can you going over the independent/dependent parameters in class?" (Yes. Exhaustively so.)

"I would really like to know if you plan on keeping the flipped-classroom style for next semester." (Yes. But as you've seen so far this semester, I'm adapting and changing how to best use this style of instruction, and will plan to do so through next semester.)

"Q: What do physicists enjoy doing the most at sporting events? A: The Wave."

Online reading assignment: medium-mass stars, massive stars, neutron stars and black holes (NC campus)

Astronomy 210, fall semester 2013
Cuesta College, San Luis Obispo, CA

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 questions were asked on reading textbook chapters and previewing presentations on the evolution of medium-mass stars, massive stars, and on neutron stars and black holes.

Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.

"I thought that what happens to stars after they die was pretty interesting because out sun is a star."
"That once a star uses up all its hydrogen, it keeps trying to stay alive by resorting to harder and harder elements to fuse for energy. Kind of like it's almost alive."

"I found interesting that stars must 'eat' hydrogen to survive and it is the most 'nutritious' stuff for them to eat."

"The idea of a star sucking up the hydrogen of another star is interesting. I guess I just like big explosions, but I also wonder if it's possible that other things could occur than just explosions."

"That you can't see black holes. Dumb TV shows."

"I found what happens to stars after they 'die' most interesting because I always wondered if they exploded or what not. It was also interesting learning about the differences of each specific type of star after they die."

"I thought it was cool to read about how a sugar cube of a neutron star on Earth would weigh approximately the same as a mountain, that is freaking amazing and confusing at the same time. It just amazes me how the mass is so dense, it doesn't even seem possible."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.

"I don't understand why a white dwarf would have enough gravity to suck hydrogen away from a star that is still going. I would have assumed that the star that is still fusing would have more mass and pull the dwarf towards it."

"I don't understand the purpose of a black hole and what goes in there, also are there many in our galaxy?"

"Black holes. They are pretty crazy. I'm confused about how scientists detect them and what is happening inside of a black hole. I think it is because it feels so unrealistic I am not able to grasp it."

A Hummer H2 and a SmartCar ForTwo can travel the same distance with a full tank of gas. Briefly explain how this is possible.

"The Hummer has a much larger gas tank than the SmartCar. This enables the Hummer to go the same distance although it eats up fuel at a much higher rate."

"I don't understand how that could be."

"I don't think this is possible, Hummers waste a lot of gas..."

"I would have never guessed about the Hummer/SmartCar thing. It makes sense though and I guess that's why I'm seeing more and more of those little Tonka™ cars zipping around."

These main-sequence stars will become which type of stellar remnant?
(Only correct responses shown.)

Massive main sequence star: (neutron star or black hole) [91%]
Medium-mass main-sequence star: white dwarf [82%]
Low-mass main-sequence star: (no stellar remnant observed yet) [55%]

These main-sequence stars could undergo which type of explosion?
(Only correct responses shown.)

Massive main sequence star: type II supernova [82%]
Medium-mass main-sequence star: (nova or type Ia supernova) [91%]
Low-mass main-sequence star: (no explosion possible) [41%]

If you were to leap into a black hole, your friends would typically watch you falling in for __________ before you entered the event horizon.

seconds.	** [2]
hours.	* [1]
days.	[0]
a year.	[0]
many years.	* [1]
forever.	*************** [15]
(Unsure/guessing/lost/help!)	*** [3]

The first rule of astronomy class is...

"...sit down, shut-up and let P-dog drop some knowledge on your ass."

"...be afraid. Be very afraid."

"...1. P-dog is the boss. 2. Follow rule number 1."

"...do not talk about astrology in astronomy class."

"...the professor's name is not 'Dr. Len.'"

"...come to class?"

"...abandon all hope."

"...you do not talk about astronomy class."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"What is the first rule of astronomy class?"

"Why is your class so badass?" (It's not me, it's you. You make this class badass.)

"Your Halloween t-shirt was funny! Kitty Scissorhands!" (Really? Not Frisky Krueger?)

Online reading assignment: medium-mass stars, massive stars, neutron stars and black holes (SLO campus)

Astronomy 210, fall semester 2013
Cuesta College, San Luis Obispo, CA

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 questions were asked on reading textbook chapters and previewing presentations on the evolution of medium-mass stars, massive stars, and on neutron stars and black holes.

Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.

"A black hole cannot be seen."

"A SmartCar and a Hummer have the same range on a full fuel tank."

"Because some stars are convective and others aren't, it completely determines the lifespan of that star, because convective stars are given more access to hydrogen fuel to stay alive."

"Once a medium-mass star has reached the end of its main-sequence lifetime, it begins to stave off 'starvation,' becoming a giant. I think it is interesting that the medium mass star becomes a giant."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.

"Black holes and spacetime--how they begin, and effects on spacetime."

"I don't understand the purpose of a black hole and what goes in there, also are there many in our galaxy?"

"The different types of stars and their explosions and remnants."

"How two stars can be born at the same time, but due to their different masses, evolve at different rates. How much quicker/slower will a smaller mass star evolve than a larger mass star?"

"Pulsars--I still do not exactly understand what it is and its importance in science."

"I find it confusing that no low mass stars have died yet."

"Black holes again. I don't understand how something can have infinite density and how if you're falling into a black hole it looks like you're falling forever from an outside observer. This is wrinkling my brain!"

"There was nothing confusing--it was just quite a bit of information to remember."

"It seems that a white dwarf is needed to form both a type Ia supernova and a nova. Both phenomena seem similar to each other but can't possibly be related."

A Hummer H2 and a SmartCar ForTwo can travel the same distance with a full tank of gas. Briefly explain how this is possible.

"Even though the Hummer H2 gets lower mileage than the SmartCar, it has a bigger fuel tank."

"The Hummer has a much larger tank. It might not burn the fuel as efficiently but it has a lot more fuel to begin with."

"This is possible because they are traveling the same distances."

These main-sequence stars will become which type of stellar remnant?
(Only correct responses shown.)

Massive main sequence star: (neutron star or black hole) [84%]
Medium-mass main-sequence star: white dwarf [61%]
Low-mass main-sequence star: (no stellar remnant observed yet) [49%]

These main-sequence stars could undergo which type of explosion?
(Only correct responses shown.)

Massive main sequence star: type II supernova [63%]
Medium-mass main-sequence star: (nova or type Ia supernova) [86%]
Low-mass main-sequence star: (no explosion possible) [26%]

If you were to leap into a black hole, your friends would typically watch you falling in for __________ before you entered the event horizon.

seconds.	***** [5]
hours.	* [1]
days.	** [2]
a year.	** [2]
many years.	* [1]
forever.	*************************** [27]
(Unsure/guessing/lost/help!)	***** [5]

The first rule of astronomy class is...

"...refer to your instructor as P-dog."

"...come to class?"

"...to have fun?"

"...to meet the Math 123, Math 123SI, or the equivalent prerequisite?"

"...don't stare directly at the sun."

...get a good grade."

"...you do not talk about astronomy class."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"What's the second rule of astronomy class?"

"I am still a little confused on the three categories of stars and their explosions and remnants." (I will go over some of these in class...just so long as you remember the first rule of astronomy class.)

"Does a black hole lead to other dimensions?" (Maybe. Let me know when you find out.)

Online reading assignment: ideal fluid flow, elasticity

Physics 205A, fall semester 2013
Cuesta College, San Luis Obispo, CA

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 questions were asked on reading textbook chapters and previewing a presentation on ideal fluid flow and elasticity.

Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.

"Stress, strain, Hooke's law and elastic modulus were particularly interesting. I was trying to figure out a while ago if a specific straightedge made of high-carbon tool steel would deflect more cantilevered under its own weight than a specific straightedge made of aluminum. I made some guesstimations after some web searching but I'm getting close to being able to make my own estimations."

"That not all fluid types are ideal. I thought they were all the same."

"An ideal fluid should undergo laminar flow, where the adjacent particles flow smoothly past each other, as opposed to turbulent flow, where particles swirl around in a chaotic manner. I like the fact that many fluids, like water can undergo both laminar and turbulent flow."

"That the side of a smaller volume tube makes up for the volume shortage by just increasing the speed of whatever is going through it. I never gave it much thought, so it is interesting to fill in the blanks for everyday examples for physics."

"Watching the car in the wind tunnel was interesting because of the streamlines."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.

"Bernoulli's equation was a bit confusing because there are a lot of variables."

"So when a hose is collapsing, the pressure in that section of hose is decreased. Is the same true in a rigid pipe? That is, when the pipe's diameter decreases, does the pressure in that section decrease as well, regardless of whether or not the pipe is rigid?"

Describe at least one property ideal fluids have that real fluids don't have.

"An ideal fluid is not compressible."

"Ideal fluids have no viscosity."

"The particles are able to smoothly slip past each other rather than bump into each other and cause turbulence."

"Ideal fluids are always incompressible, they undergo laminar flow, and they also have no viscosity."

What are the SI units for volume flow rate?

"m³/s."

"kg/s."

In Bernoulli's equation, what are the SI units for the ρ·g·y term, and for the (1/2)·ρ·v² term?

"Joules."

"J/m³."

"Pa."

An ideal fluid flowing from left-to-right along an expanding cross-section tube would experience a decrease in:

speed.	****************** [18]
volume flow rate.	******** [8]
(Both of the above choices.)	******** [8]
(Unsure/guessing/lost/help!)	*** [3]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"Q: When do sheep most like to go swimming in the river? A: When the flow is lamb-inar."

"Can you super-explain this section please! Bernoulli's equation. Practice problems?" (Yes, yes, yes--there will be time set aside in class for these.)

"I may be stressed, but I remain free from strain (for now)."

"I don't ever feel prepared for this class, no matter how much I read or do problems." (But you've tried, so you at least know what you don't know, and are letting me know what you need to know from class.)

"This flipped classroom method is still exacerbating my ability to learn in this class."

"What did you dress up as for Halloween?" (Nothing special. I just wore this t-shirt.)

"Will you be using the flipped classroom style in Physics 205B next semester?" (Imma try.)