Online reading assignment: heat transfers

Physics 205A, fall semester 2012
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 heat transfers.

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.

"How you can touch a Space Shuttle tile even when it has a ton of internal energy! I don't quite understand how so it is very interesting to me!"

"How a blackbody is really good at absorbing heat from light and is also a good radiator of heat, and a silverbody being the opposite."

"How Coffee Joulies^TM cools down coffee yet keeps it warm longer."

"The windowpane problems really hit home with how much dual-pane windows conserve heat in the home (and mainly from the air gap)."

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

"I found much of this confusing because I have never dealt with it before."

"Fourier's law of conduction. Stefan's law of radiation. Wien's law."

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

"Still trying to grasp the reason why heat flows from hot to cold to reach thermal equilibrium." (This is merely a restatement of the zeroth law of thermodynamics--and this is something that is always observed to happen on its own in nature.)

"How is a kilocalorie the same as a calorie?" (A kilocalorie is a thousand calories. But a kilocalorie is equal to a Calorie (capitalized), also known as a 'food calorie.' No one wants to eat a 100,000 calorie candy bar (i.e., 100 kilocalories), but one would be more than willing to eat the same candy bar labeled as '100 Calories.'")

"What are Coffee Joulies^TM?" (You can investigate how well a crude model of this device works in next week's laboratory.)

"Real-life example of a blackbody?" (Your car radiator, which is painted black in order to most effectively radiate heat, instead with of a light-colored or reflective surface.)

"I thought that if you had an 'A' in the class, you didn't have to take the Final Exam. Since we can earn 600/700 points (85.7%), and before the final 600 points are possible, shouldn't we be excused from the Final Exam if we have earned 514/575 points? That's more than 85.7% so far." (No. Your grade is determined by the total points, not by the average. This is so your grade cannot go down (as an average might), but can only go up (by accumulating more points). That's just how it is.)

"For the Final Exam will we need Scantrons?" (No, the Final Exam will be similar to the midterms (writing your answers on the exam itself), and will consist of four short-answer questions and three worked-out problems.)

Online reading assignment: runaway planets, jovian planets, and dwarf planets (oh my!) (SLO campus)

Astronomy 210, fall semester 2012
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 runaway planets (Venus and Mars), jovian planets (Jupiter, Saturn, Uranus and Neptune), and the impacted worlds: dwarf planets (and the International Astronomy Union classification scheme).

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 large impact on Uranus, that caused that planet to be the only one who has a tilted axis, and caused it to cool off faster than Neptune."

"I never knew how the International Astronomical Union decided that Pluto wasn't a planet!"

"How massive planets retain heat longer than less massive planets, and how more mass is good for building and retaining an atmosphere for the greenhouse effect."

"The many comparisons and contrasts between Venus and Mars. At times it's hard to remember which planet is which, and which has certain specific characteristics. But, I enjoyed learning about these two planets."

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

"All the planets are so different! It confuses me how they all ended up so different."

"'Runaway planets' seem confusing because I don't understand how they can 'runaway' or what causes them to."

"Jovian planets, because there really is no solid surface there, and that's hard for me to grasp."

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

"Why am I failing?" (I checked your score, and everyone else's in class as well--no one going to fail this class, unless you happen stop caring, or stop coming to class (or die, which to me would be the same thing). Or maybe you mean failing to live up to your expectations.)

"Why is Haumea, who has a sort of oval/flat shape, considered a dwarf planet? And can you explain the criteria of what makes a dwarf planet?" (Haumea is massive enough to retain heat to melt and gravitationally reform itself into a rounded shape; its oblateness is due to its rapid rotation, which stretched its shape out while it was molten into a very flattened ellipsoid instead of a sphere. But it is a dwarf planet rather than a planet because it does not gravitationally dominate its orbit around the sun.)

"How hard is the final compared to the midterms? When will we know what will be on the Final Exam?" (Next week at this time the study guide for the Final Exam will be posted. It is the same length and difficulty as a midterm, but will be comprehensive, with a slight emphasis on the material covered since the second midterm.)

"If Pluto was once a planet I feel that it should stay a planet." (That's what they told Ceres, Pallas, Vesta, and some others more than a hundred years ago...until they demoted them all from planet status as well.)

"What do you think about Pluto not being considered a planet? I loved Pluto as a child and I don't like the change." (One day, in the future, your children will be amused at your old-fashioned ideas.)

Astronomy current events question: Abell 399 and Abell 401 hot gas bridge

Astronomy 210L, fall semester 2012
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, "Planck Spots Colossal Intergalactic Bridge," November 20, 2012
http://www.nasa.gov/mission_pages/planck/news/planck20121120.html

NASA's Planck Space Telescope confirmed the existence of a bridge of hot gas connecting a pair of galaxy clusters by detecting how this gas interacts with:
(A) antimatter.
(B) new star formation.
(C) cosmic background radiation.
(D) dark matter.
(E) super-Jupiters.

Correct answer: (C)

Student responses
Sections 70178, 70186, 70200
(A) : 2 students
(B) : 1 student
(C) : 19 students
(D) : 4 students
(E) : 0 students

Astronomy current events question: Large Underground Xenon experiment

Astronomy 210L, fall semester 2012
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!)

Bill Harlan, "Dark Matter Detector Submerged in Water Tank," November 15, 2012
http://www.sanfordlab.org/news/press_release/dark-matter-detector-submerged-water-tank

The Large Underground Xenon experiment in South Dakota to detect dark matter is installed deep underground in a water-filled tank in order to:
(A) cool down its components.
(B) shield it from cosmic radiation.
(C) protect it from earthquake tremors.
(D) contain radioactive emissions.
(E) inhibit corrosion.

Correct answer: (B)

Student responses
Sections 70178, 70186, 70200
(A) : 2 students
(B) : 19 students
(C) : 1 student
(D) : 4 students
(E) : 0 students

Astronomy current events question: super-Jupiter Kappa Andromedae b

Astronomy 210L, fall semester 2012
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!)

National Astronomical Observatory of Japan Subaru Telescope press release, "Direct Imaging of a Super-Jupiter Around a Massive Star," November 19, 2012
http://www.naoj.org/Pressrelease/2012/11/19/index.html

The National Astronomical Observatory of Japan's Subaru Telescope in Hawaii directly imaged a "super-Jupiter" planet orbiting the star Kappa Andromedae by:
(A) illuminating it with laser beams.
(B) observing during a total solar eclipse.
(C) subtracting out light from the star.
(D) borrowing Hubble Space Telescope observing time.
(E) using gravitational lensing.

Correct answer: (C)

Student responses
Sections 70178, 70186, 70200
(A) : 3 students
(B) : 6 students
(C) : 28 students
(D) : 3 students
(E) : 12 students

Astronomy current events question: Makemake atmosphere

Astronomy 210L, fall semester 2012
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!)

José Luis Ortiz, Bruno Sicardy, Noemi Pinilla-Alonso, Emmanuel Jehin, and Richard Hook, "Dwarf Planet Makemake Lacks Atmosphere," November 21, 2012
http://www.eso.org/public/news/eso1246/

Astronomers at the European Southern Observatory in Chile have determined that dwarf planet Makemake does not have an atmosphere by:
(A) counting impact craters.
(B) how it eclipsed a star.
(C) using adaptive optics.
(D) detecting no polar ice caps.
(E) tracking its five moons.

Correct answer: (B)

Student responses
Sections 70178, 70186, 70200
(A) : 7 students
(B) : 23 students
(C) : 9 students
(D) : 2 students
(E) : 1 student

Online reading assignment: runaway planets, jovian planets, and dwarf planets (oh my!) (NC campus)

Astronomy 210, fall semester 2012
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 runaway planets (Venus and Mars), jovian planets (Jupiter, Saturn, Uranus and Neptune), and dwarf planets (and the International Astronomy Union classification scheme).

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 specifics of the other planets in our solar system, because I am tired of learning about Earth, and I would like to know about what else is out there."

"The IAU rules for classifying solar system objects, because it's interesting how scientists determine if something is a planet or not."

"The video of Saturn that used NASA footage was beautiful."

"Why the core of a planet like Uranus would be cooler, like a baby bottle we are trying to cool by shaking it. Awesome example."

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

"Why the core of Uranus is colder than Neptune. I don't understand how Uranus could be impacted with so much force that its axis would change position."

"How the atmospheres of the jovian planets differ so much."

"How they determine if something is a dwarf planet or a planet."

"How Earth is the only planet, that we know of, that supports life. How is it that Earth evolved into this place that is so perfect for so many different types of life, yet some of the other planets have similar components, gases and atoms, that are capable of supporting/becoming life--but they didn't and haven't? Why?"

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

"Will the Final Exam suck my grade down to a bottomless pit like a black hole?" (Your total points so far, including the second midterm are posted online. And no, you can only gain points from here on out, in order to raise your grade.)

"At this stage all I can say is thank you. Perhaps you don't see it, but there aren't many teachers like you any more. I'm really glad I decided to take this class." (It's not me, it's the subject matter. Astronomy. ASTRONOMY RULES.)

"Do you believe Pluto should be a planet? I'm a 90's kid--I have to believe Pluto is a planet." (One day, in the future, your children will call you old-fashioned for doing so.)

Online reading assignment: internal energy

Physics 205A, fall semester 2012
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 internal energy.

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.

"How heat and work are energy transfers and not a type of energy that one object may possess. Heat and work can only be transfers."

"Heat isn't just how hot something is."

"In older times heat was thought to be a liquid."

"Who everyone thinks is the hottest Lord of the Rings character. That should have been a question."

"A change in the internal energy of a system does not always cause a temperature change. the internal energy of a system can change while the temperature remains constant like ice melting. I would have assumed that internal energy would always change temperature."

"I remember a lot of this from chemistry. :)"

"How we aren't going to go into detail about thermodynamics from a chemistry or engineering point of view. I have a very good understanding of thermodynamics in chemistry, so I am interested to learn about thermodynamics from a physics point of view."

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

"Perhaps you could talk a little about thermal equilibrium."

"This whole chapter seems like it will be confusing."

"'Specific' heat capacity and heat capacity, and what the difference is."

"I'm hoping that this will get easier this time around. I struggled a little with heat/energy in chemistry."

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

"Isn't the specific heat of water annoying, especially when your trying to make a cup of tea or trying not to freeze to death when your soaked in a snowstorm?" (To quote Alexander Solzhenitsyn, "How can you expect a man who is warm to understand one who is cold?")

"How many more chapters are we going to cover by the end of this semester?" (This chapter--Chapter 14--is the last for this semester.)

"I wish there would be more extra credit. I wish to improve my grade. Therefore, I will try my best again in finals." (I can only grant you one of those wishes. The rest is up to you.)

"Do you have an advice for us so it is easier to remember how and when to use the heat or how it flows?" (It's not too hard, but let's see how you do on the flashcard questions in class.)

Physics midterm question: Chevrolet Camaro ZL1 power output

Physics 205A Midterm 2, fall semester 2012
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problems 6.71, 6.75

A 2013 Chevrolet Camaro ZL1 (mass 1,984 kg) on a horizontal track takes 8.8 s to accelerate from 13 m/s to 22 m/s, and then takes 7.7 s to accelerate from 22 m/s to 31 m/s[*]. Which process used a greater average mechanical power output from the engine?
(A) Accelerating from 13 m/s to 22 m/s.
(B) Accelerating from 22 m/s to 31 m/s.
(C) (There is a tie.)
(D) (Not enough information is given.)

[*] "Curb weight: 4,373 lb; Top gear, 30–50 mph: 8.8 sec; Top gear, 50–70 mph: 7.7 sec," caranddriver.com/reviews/2013-chevrolet-camaro-zl1-convertible-test-review.

Correct answer (highlight to unhide): (B)

The mechanical output of the car's engines does non-conservative work to increase translational kinetic energy:

W_nc = ∆KE_tr,

where the average power output of the car's engines is the rate of work done per time:

P_av = W_nc/∆t = ∆KE_tr/∆t.

For accelerating from 13 m/s to 22 m/s, the engine power output is:

P_av = (1,984 kg)·((22 m/s)² – (13 m/s)²)/(8.8 s) = 3.5×10⁴ watts,

and for accelerating from 22 m/s to 31 m/s, the engine power output is:

P_av = (1,984 kg)·((31 m/s)² – (22 m/s)²)/(7.7 s) = 6.1×10⁴ watts.

Thus accelerating from 22 m/s to 31 m/s in 7.7 s requires more power output for this car than accelerating from 13 m/s to 22 m/s in 8.8 s.

Sections 70854, 70855
Exam code: midterm02gL0u
(A) : 7 students
(B) : 45 students
(C) : 2 students
(D) : 0 students

Success level: 83%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.33

Physics midterm question: descending, widening pipe

Physics 205A Midterm 2, fall semester 2012
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problems 9.41, 9.45

The pressure of water __________ as it flows from point [1] to point [2]. (Assume ideal fluid flow.)
(A) decreases.
(B) remains constant.
(C) increases.
(D) (Not enough information is given.)

Correct answer (highlight to unhide): (C)

From applying the continuity equation:

A₁·v₁ = A₂·v₂,

the water speed at point [2] is slower than at point [1], because the cross-sectional area at point [2] is larger than at point [1].

Then from Bernoulli's equation:

0 = ∆P + (1/2)·ρ·∆(v²) + ρ·g·∆y,

the second term on the right-hand side decreases due to the decrease in speed from point [1] to point [2], while the third term on the right-hand side decreases (as the elevation decreases along the pipe), thus the pressure must increase as water flows from point [1] to point [2].

Sections 70854, 70855
Exam code: midterm02gL0u
(A) : 21 students
(B) : 5 students
(C) : 26 students
(D) : 1 student

Success level: 48%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.26