20191116

Astronomy current events question: warm dust radio wave glow from "Cosmic Yeti" galaxy

Astronomy 210L, fall semester 2019
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!)
News release, "Cosmic Yeti from the Dawn of the Universe Found Lurking in Dust" (October 22, 2019)
uanews.arizona.edu/story/cosmic-yeti-dawn-universe-found-lurking-dust
The Atacama Large Millimeter Array in Chile detected radio waves given off by __________ surrounding rapidly forming stars in a massive monster galaxy when the universe was very new.
(A) warm dust.
(B) dark matter.
(C) gravitational waves.
(D) hydrogen-rich clouds.
(E) matter and antimatter.

Correct answer: (A)

Student responses
Sections 70178, 70186
(A) : 25 students
(B) : 2 students
(C) : 1 student
(D) : 9 students
(E) : 1 student

Astronomy current events question: BD +20 307 exoplanet collision

Astronomy 210L, fall semester 2019
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!)
Kassandra Bell, "When Exoplanets Collide" (October 22, 2019)
news.ucsc.edu/2019/10/exoplanets-collide.html
Recent evidence of increasing __________ indicate that the collision between two rocky exoplanets in the BD +20 307 star system may have happened relatively recently.
(A) surface reflectivity.
(B) greenhouse effect.
(C) ocean acidification.
(D) infrared brightness.
(E) volcanic outgassing.

Correct answer: (D)

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

Astronomy current events question: K-Pg asteroid impact ocean acidification

Astronomy 210L, fall semester 2019
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!)
Jim Shelton, "Mystery Solved: Ocean Acidity in the Last Mass Extinction" (October 21, 2019)
news.yale.edu/2019/10/21/mystery-solved-ocean-acidity-last-mass-extinction
Researchers confirmed that ocean acid levels rose sharply following the K-Pg asteroid impact, based on analyzing the chemical composition of __________ fossils.
(A) mammal.
(B) plankton.
(C) dinosaur.
(D) protobird.
(E) protowhale.

Correct answer: (B)

Student responses
Sections 70178, 70186
(A) : 0 students
(B) : 33 students
(C) : 1 student
(D) : 1 student
(E) : 3 students

20191114

Physics quiz question: Young's modulus of steel

Physics 205A Quiz 6, fall semester 2019
Cuesta College, San Luis Obispo, CA

A sample of "#4" steel reinforcing bar has a length of 4.9 m and a cross-sectional area of 1.3×10–4 m2. A force of 1.1×105 N is applied to stretch this steel bar by 0.020 m. The Young's modulus of steel is:
(A) 3.5×106 N/m2.
(B) 8.5×108 N/m2.
(C) 4.2×1010 N/m2.
(D) 2.1×1011 N/m2.

[*] webcivil.com/usrcrebar.aspx.

Correct answer (highlight to unhide): (D)

Hooke's law is given by:

(F/A) = Y·(∆L/L),

such that the Young's modulus would be:

(F/A)·(L/∆L) = Y = ((1.1×105 N)/(1.3×10–4 m2))·((4.9 m)/(0.020 m)),

Y = 207,307,692,307.692 N/m2,

or to two significant figures, the Young's modulus for steel is: 2.1×1011 N/m2.

(Response (A) is (F/A)·(∆L/L); response (B) is F/A; response (C) is F/(A·∆L).)

Sections 70854, 70855
Exam code: quiz06co6O
(A) : 5 students
(B) : 2 students
(C) : 2 students
(D) : 43 students

Success level: 83%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.50

20191113

Physics quiz question: amount of mass attached to a spring

Physics 205A Quiz 6, fall semester 2019
Cuesta College, San Luis Obispo, CA

A mass is attached to a horizontal spring (with a spring constant of 
40 N/m), and has a 0.80 s period of oscillation. Neglect friction and drag. The mass attached to this spring is:
(A) 0.13 kg.
(B) 0.16 kg.
(C) 0.65 kg.
(D) 5.1 kg.

Correct answer (highlight to unhide): (C)

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

T = 2·π·√(m/k),

such that the mass m will be:

T/(2·π) = √(m/k),

(T/(2·π))2 = m/k,

k·(T/(2·π))2 = m = 0.6484555753 kg,

or two significant figures, the mass attached to the spring is 0.65 kg.

(Response (A) is T/(2·π); response (B) is (2·π)/k; and response (D) is k·T/(2·π).)

Sections 70854, 70855
Exam code: quiz06co6O
(A) : 1 students
(B) : 4 students
(C) : 45 students
(D) : 2 students

Success level: 87%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.39

Physics quiz question: finding acceleration due to gravity from pendulum

Physics 205A Quiz 6, fall semester 2019
Cuesta College, San Luis Obispo, CA

The California Academy of Sciences in San Francisco has a pendulum with a period of 6.406 s, consisting of a 106.6 kg ball attached to a 10.20 m long wire hanging from the ceiling. Assume that the ball can be considered a simple point mass. Neglect friction and drag. The magnitude of the acceleration due to gravity g at that location is:
(A) 9.432 m/s2.
(B) 9.620 m/s2.
(C) 9.808 m/s2.
(D) 9.813 m/s2.

[*] kathleensf.files.wordpress.com/2008/07/the-foucault-pendulum-at-the-california-academy-of-sciences-december-14-2010.pdf.

Correct answer (highlight to unhide): (D)

The period of a pendulum is given by:

T = 2·π·√(L/g),

Since the period T = 6.406 s and string length L = 10.20 m are known, the acceleration due to gravity g can then be solved for:

T/(2·π) = √(L/g),

(T/(2·π))2 = L/g,

g = L·((2·π)/T)2,

g = (10.20 m)·((2·π)/(6.406 s))2 = 9.8126439271 m/s2,

or to four significant figures, the acceleration due to gravity is 9.813 m/s2.

(Response (A) is (1/L)·((2·π)/T)2; response (B) is 10·((2·π)/T)2); response (C) is 10·((2·π)/T).)

Sections 70854, 70855
Exam code: quiz06co6O
(A) : 1 student
(B) : 5 students
(C) : 9 students
(D) : 37 students

Success level: 71%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.44

Physics quiz question: linear mass density of viola string

Physics 205A Quiz 6, fall semester 2019
Cuesta College, San Luis Obispo, CA

Transverse waves travel at a speed of 357 m/s along a viola's A-string, stretched to a tension of 52.9 N[*][**]. The linear mass density of this string is:
(A) 4.15×10–4 kg/m.
(B) 2.20×10–2 kg/m.
(C) 0.148 kg/m.
(D) 0.385 kg/m.

[*] theviolaworkshop.com/page16.html.
[**] gamutmusic.com/viola-tensions.

Correct answer (highlight to unhide): (A)

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

v = √(F/(m/L)).

Solving for the linear mass density results in:

v2 = F/(m/L),

(m/L) = F/(v2),

(m/L) = (52.9 N)/(357 m/s)2 = 0.000415067988 kg/m,

or to three significant figures, 4.15×10–4 kg/m.

(Response (B) is (F/v)2; response (C) is F/v; response (D) is √(F/v).)

Sections 70854, 70855
Exam code: quiz06co6O
(A) : 35 students
(B) : 7 students
(C) : 8 students
(D) : 2 students

Success level: 67%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.78

Physics quiz archive: simple harmonic motion, waves

Physics 205A Quiz 6, fall semester 2019
Cuesta College, San Luis Obispo, CA
Sections 70854, 70855 version 1
Exam code: quiz06co6O



Sections 70854, 70855 results
0- 6 :   * [low = 3]
7-12 :   ****
13-18 :   *************
19-24 :   **************** [mean = 22.1 +/- 6.1]
25-30 :   ****************** [high = 30]

Online reading assignment: temperature

Physics 205A, fall semester 2019
Cuesta College, San Luis Obispo, CA

Students have a bi-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 what you understand from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically demonstrate your level of understanding.
"Temperature plays a big role in thermal stress with expansion or contraction. This can be used to our advantage or disadvantage."

"I understand that if the liquid expansion is greater than the container expansion, there will be overflow. Vice versa, there will be no overflow. Expansion occurs as a response to temperature change."

"Explaining a thermometer: temperature ultimately 'is' something greater than the feeling that something is hot or cold; rather, change in temperature is the expansion of materials. In the case of a thermometer, the red alcohol experiences a temperature increase expanding its volume filling up more of the glass indicating a temperature change."

"It totally didn't occur to me how objects expand depending on differences in temperature. It just isn't something that's on my mind daily, but now that I've read about it, it clearly makes sense. I understood the concept of the length of steel beams and how shorter beams would require a higher temperature to expand compared to longer ones."

"The more heat applied the greater an object will expand the size of the expansion is proportional to the size of the object. The same is true for chilling an object."

"That the forces needed to prevent a solid object from expanding must be strong enough to counteract any change in length that would occur due to a change in temperature. It makes sense to me that the change in forces can result in serious structural damage."

Describe what you found confusing from the assigned textbook reading or presentation preview. Your description (2-3 sentences) should specifically identify the concept(s) that you do not understand.
"I do think I could use some extra examples covering linear thermal expansion and volume thermal expansion. These practice problems given were confusing to me."

"I had trouble understanding thermal stress and how it differs from normal stress. I was also confused by some of the equations for linear and volume thermal expansion."

"The linear and volume expansion formulas."

"I do not understand the concept behind why objects or fluids expand because of temperature change. Also, does heat mean expansion and cold mean shrink? Does it simply depend on the object?"

"I think I get the general concept of this, but I'm looking forward to the lecture and seeing how these equations will work out."

"Nothing was too crazy, just need to keep in mind how the equations work."

"The reading got more confusing as it went on. At the end, when it was discussing which time of day that the gas would be higher, I was not sure of the answer. "

For solids, what is the mathematical relationship between the coefficient of volume expansion β and the coefficient of linear expansion α?
"β = 3·α."

"The mathematical relationship between the coefficient of volume expansion and the coefficient of linear expansion is that the coefficient for volume expansion is three times as much as the coefficient of linear expansion."

To expand these two steel beams 1.0 cm from their original lengths, the longer beam will require __________ temperature increase compared to the shorter beam.
a smaller.  ******************* [19]
the same.  **** [4]
a larger.  **** [4]
(Unsure/guessing/lost/help!)  * [1]

For a thermometer, the glass volume expansion coefficient 3αglass is __________ the alcohol volume expansion coefficient βalcohol.
less than.  ************** [14]
equal to.  ****** [6]
greater than.  ****** [6]
(Unsure/guessing/lost/help!)  ** [2]

For the water level in this plastic rainwater basin to lower as the temperature falls overnight, the plastic volume expansion coefficient 3αplastic must be __________ the water volume expansion coefficient βwater.
less than.  *********** [11]
equal to.  ***** [5]
greater than.  ************************ [24]
(Unsure/guessing/lost/help!)  ****** [6]

A certain fuel company will measure out a gallon of gasoline and sell it for the same price, whether it is cool or warm. Indicate the gallon of gasoline that has a greater:
(Only correct responses shown.)
mass: the cool gallon [35%]
density: the cool gallon [76%]

Briefly explain why a gallon of gasoline purchased when it is cool would be better than a gallon of gasoline purchased when it is warm. (In either case, the fuel company dispenses the same volume of exactly one "standard" gallon.)
"Colder gasoline is more dense than warmer gasoline, so a cold gallon of gas contains more energy than a warm gallon of gas, even though they might cost the same."

"Chemically, cooling down allows for the molecules to slow and move closer together, allowing for the density to increase."

"When the gas is cooler it becomes denser and you actually end up with more molecules of gas per gallon."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"This class is going by so fast!"

"Just need to talk this over in class."

"I never knew they had to account for expansion when constructing sidewalks."

"I would love to go over the gasoline question a bit more."

"Why do objects expand and shrink with temperature change?" (The atoms and molecules inside move faster when hotter. But because of asymmetry of the spring-like interactions between the atoms and molecules, it is harder for them to move closer together (because of mutual repulsion) than it is for them to move farther apart, and so overall the object will expand.)

"Will we be experimenting with liquids during the next lab?" (Actually, we'll be finishing up with standing waves for the last lab.)

"Sad you didn't dress up as an astronaut again for Halloween this year :("

20191112

Online reading assignment: Milky Way history, big bang clues (NC campus)

Astronomy 210, fall semester 2019
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 history of the Milky Way and big bang clues, a comic strip adaptation of Neil deGrasse Tyson's "The Most Astounding Fact" 2008 interview for TIME magazine, and Minute Physics' video explanation of Olbers' paradox.


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 big bang."

"The 'top-down' hypothesis of how the Milky Way galaxy was formed, and the big bang theory since both explain theories of how things came to be."

"I like how when we look at the stars we could be looking at a star that's possibly already dead."

"Watching the video about how astronomers measure the distance in light stars to a star was very interesting, it was a question I had on my mind when we briefly started talking about lightyears in class. I am still genuinely curious how it the math goes down step by step."

"That we are basically made up of stuff from stars that went supernova; so we are made up of dead stars that gave us the materials to make other stars and planets and eventually would lead to life using metals like iron, calcium, carbon, oxygen, and nitrogen that help to form the basic building blocks of life that would eventually lead to us."

"Learning about galaxies was pretty interesting, but it takes on a whole new layer of intrigue when we're talking about our own galaxy. Very cool."

"I found it interesting that the universe isn't finite but that it is infinite and that the universe may have a starting date meaning that there was a certain time that it didn't exist until it did."

"That for stars such as Deneb when we DO see them we're looking at its past form, not its current state."

"One thing I found interesting was the finite speed of light. It turns out that we have a time-machine of sorts to actually see the universe as it was in the past."

"It's comforting knowing that the galaxy is pretty much responsible for polluting itself. Humans haven't totally ruined everything. And the Milky Way is essentially a disgusting extra smog day in Los Angeles. Eeek! I also appreciated learning how light years are calculated and found it completely mind-blowing that I have looked at what a galaxy [Andromeda] looked like 25.4 million years ago. This is one thing that I wrote down at the beginning of the semester that I wanted to learn."

"The big bang theory because you always hear people say it, but I never knew what it actually was."

"I really like the Zen Pencils comic strip because it involves life in the universe."

"How everything in general is pretty much made up of metals/dirt, which sorta (not really) debunks my 'space is mystical' thing."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"I need a bit more clarification on the big bang theory, other than that everything was pretty straightforward."

"I was tripping out on that video that talked about why the space is black, so is it black because when we look at space we are actually looking at space in the past? Please go over this a bit."

"It is puzzling that we don't know if there is a true edge of the universe. And what happens if the universe has an edge? How does that affect our understanding of the universe?"

"Light years are a concept that continue to confuse me."

"Look-back time. And how do you calculate how far another galaxy is?"

"The 'gaps' between galaxies."

"Does hydrogen turn into the metals and how?"

"I am not understanding the differences between a halo and a disk as it refers to the Milky Way's different formations. They both seem the same to me."

"Trying to grasp the concept with an open mind as an infinite anything is hard to think of as well as that at one time there were no stars or anything is just hard to wrap my mind around."

"The Hubble law."

"The Hubble law, which sounded interesting, also kind of lost me a little."

Indicate how the amount of these elements in the universe have changed over time.
(Only correct responses shown.)
Hydrogen: decreased [33%]
Metals (elements heavier than hydrogen and helium): increased [73%]

The outermost layers of __________ are more abundant in metals (elements heavier than hydrogen and helium).
extremely old stars that formed a long time ago.  ***** [5]
young stars that formed very recently.  ********* [9]
(There is a tie.)  [0]
(Neither, as stars cannot have metals.)  [0]
(Unsure/guessing/lost/help!)  * [1]

Indicate what produced these elements.
(Only correct responses shown.)
Hydrogen in the sun's core: the very early universe [67%]
Helium in the sun's core: the sun [40%]
Carbon in your body: another star, in the past [40%]
Calcium in your bones: another star, in the past [53%]
Iron in your blood: another star, in the past [53%]
Gold and silver from mines: another star, in the past [33%]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Is there an actual answer to what caused the big bang?" (Not yet, but asking what caused the big bang might be like asking "why does time run forward?" or "why isn't gravity both attractive and repulsive?")

"Will we learn more about the big bang theory?" (Yes, after the second midterm.)

"Could you please go over the difference between a halo and a disk as it refers to the Milky Way?" (Here's a visual explainer from the European Space Agency.)

"I really enjoyed this reading."

"I love this class!"

"We're coming up nearer and nearer to the end, I can't wait to see what else you have in store." (You'll see.)

"If the universe wasn't infinite, then would could be beyond it?" (If it turns out that the universe wasn't infinite, then if you started traveling outwards, you wouldn't keep going and going, but after a long time you would eventually return back to your starting point.)