20170926

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

Astronomy 210, fall semester 2017
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 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.
"I found that the concept behind runaway planets to be extremely interesting because I didn't realize just how differently Venus and Mars have changed and how those changes had occurred."

"I think it is really neat how Venus's volcanoes are essentially like gophers pushing themselves up until the explode suddenly. Like, goodness, the planetary conditions that support such violent and ginormous actions must be quite extreme."

"That Venus has periodically active volcanos that repave the surface."

"The differences between Earth's greenhouse effect and that of Venus and Mars."

"Learning about the greenhouse effect and how it has made other planets inhospitable for life was really interesting to me. It seems like a glimpse into Earth's future if we don't find away to reduce carbon dioxide emissions. It's also mind-boggling to me that there is still a certain percentage of the population who refuse to believe any of the evidence indicating that temperatures are rising on our planet (sad!)."

"On Venus if you could survive the stuff in the atmosphere and the intense heat, you could strap wings on your arms and fly. This is because the atmosphere is dense. This is such a weird fact, but cool."

"That Mars is actually a pretty cold planet, I always thought that it was a very hot planet for some reason. I don't really know why."

"How what we call gas giants are really more liquid giants. I had always imagined them being large orbs of gas for some reason?"

"I previously thought all planets past Mars were 'gas giants', but learning that Uranus and Neptune are actually considered 'ice giants' was pretty interesting to me."

"How Uranus is colder than Neptune even though it is closer to the sun."

"That there are other dwarf planets other than Pluto. It was just something that I didn't know."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"Something I found confusing (carrying over from last class) was deciding which formations on the terrestrial planets were formed either more or less recently. Reading about the period of heavy bombardment and each planet's unique geological history has helped me understand more but I think it may take more studying before I really get it."

"I had a hard time at first connecting the dots between the mass/outgassing slides and what was in the textbook."

"I didn't know I was confused about the comparisons between, Earth, Venus, and Mars until I started this reading assignment. I found myself doing a lot of additional digging through the book and online to answer the questions."

"How to tell which features on the planets are younger/older."

"How Jupiter's belt-zones are more visible than Saturn's. I still don't understand why that is."

"Uranus and Neptune's differences, and the 'Cooper Cooler' effect.

Identify the relative amounts of these characteristics for Venus, compared to Earth. (Only correct responses shown.)
Interior core heat, today: about the same as Earth [53%]
Geologic activity, today: less than Earth [59%]
Volcanic outgassing, up until now: about the same as Earth [56%]
Heat from the sun: more than Earth [91%]
Amount of atmosphere, today: more than Earth [81%]

Identify the relative amounts of these characteristics for Mars, compared to Earth. (Only correct responses shown.)
Interior core heat, today: less than Earth [94%]
Geologic activity, today: less than Earth [90%]
Volcanic outgassing, up until now: less than Earth [75%]
Heat from the sun: less than Earth [72%]
Amount of atmosphere, today: less than Earth [91%]

Which jovian planet has the coolest interior temperatures?
Jupiter (most massive).   [0]
Saturn (most prominent rings).   [0]
Uranus (least active weather patterns).   *********************** [23]
Neptune (farthest from the sun).   ********* [9]
(Unsure/guessing/lost/help!)   [0]

I believe Pluto should be a planet.
Strongly disagree.   ** [2]
Disagree.   ******* [7]
Neutral.   **************** [16]
Agree.   **** [4]
Strongly Agree.   *** [3]

Briefly explain your answer to the previous question (whether Pluto should be a planet).
"Pluto is small and is a different type of body, so it would not make very much sense to call it a planet, but not calling it a planet does not marginalize its position in the solar system."

"Because it fits two of the three criteria for it to be a planet; it is round, and it orbits the sun, yet it doesn't dominate its orbit, so it isn't a planet in the traditional sense, but it is a dwarf planet."

"It has the majority of the rules set forth by the IAU. It orbits the sun and has a round shape."

"Pluto orbits the sun and it is round but its orbital path isn't the same as the eight planets."

"Technically Puto is massive enough to build its spherical shape which is considered to be an aspect of a planet. It does not have enough gravitational pull to clear out other bodies near or in its orbit which would not make Pluto a planet. With these facts considered I am neutral to deciding if Pluto is a planet or not."

"It's no different than the other thousands of frozen bodies floating in its belt, considering some are slightly larger and still unrecognized as a planet."

"Not sure if it should be or not curious as to why for so long it was considered a planet but now not."

"When I was in elementary I was taught that Pluto was a planet, we need equal rights for Pluto."

"According to our book, in order for an object to be considered a planet it must be large enough to clear it's orbital region and other objects but Pluto does not do this so considering the criteria I don't think Pluto should be a planet."

"I think Pluto should be considered a planet, it always has, and always should be."

"I do think it has mostly planet characteristics, but it is really small (its moon is even almost as big as it) and isn't clear of debris so it should stay a dwarf planet."

"Because it is really a dwarf planet."

"Pluto used to be a planet, but because of IAU they have changed it. According to their classification it is not and honestly it doesn't matter much to me."

"n some level I think Pluto should be considered an honorary planet because it has been included as one in our solar system models for so long. However, since it fails to meet the IAU classification requirements the title 'dwarf planet' should be used for consistency's sake (also 'dwarf planet' is a cute descriptor)."

"I don't believe Pluto should be consider a planet because it is not big enough to dominate its orbit."

"I would have said yes Pluto should be a planet just because it's Pluto and it was weird they re-classified it, but after reading why (doesn't dominate orbit) I'm not so sure."

"I'm not sure if you want our opinion, or the scientific answer. If you are wanting my opinion I'm not to worried about wether Pluto is a planet or not."

"The astronomers and scientists needs to define a plant better. than make the concolusion regarding Pluto."

"I am neutral on this topic because mainly I don't want to piss off Pluto and have it become and asteroid that destroys us all but If these smart fellas at IAU are right about their three rule planetary ruling than I guess its safe to say that Pluto is in fact not a planet :("

"I can see why it is not considered a planet because it cannot pull itself into a spherical shape, but I also think that just because its too small to do this, doesn't mean it can't still be considered a planet."

"I just feel as though Pluto falls so closely into being a planet, that it might as well already be a planet. However, it still does lack some of the official planet criteria. So I think it could go either way."

"Pluto does not pass the third qualification of planets."

"I don't necessarily think that Pluto should or shouldn't be a planet. I can respect that it's a dwarf planet, but I don't think it's really fair to just kick it out of the main solar system planets because it's now a different classification."

"It doesn't meet the given criteria. It doesn't dominate its orbit. While it is round, and orbits the sun, it is lacking the one point that would make it a planet, therefore, I would call it a subplanet."

"I take no personal value from Pluto being a planet or not. I think if Pluto had a really good argument and all it wanted its entire life was to be a planet, then similar to sex changes, it should be able to transition."

"If it was a planet, then we would have to start including other dwarf planets."

"No, because it could not clear other objects from its path, not massive enough to do so. Resembles other family of icy new worlds like Eris."

"Pluto is a tiny but also a planet in our solar system! You can not count that it isn't because it's to 'small' or to far away. Its very very far but it is still there and we haven't collected sufficient data to consider it a non-planet!"

"I guess I just don't really view whether or not Pluto is a planet or a dwarf planet as that important in the scheme of issues today. However, that being said Pluto does orbit the sun, it is roundish in shape, and I don't really know if I can say whether or not it dominates its orbit. Based on those characteristics, I feel like it could easily be classified as either planet or dwarf planet."

"You can't declare a planet is a planet then revoke the title. That's like reaching adulthood and being called an adult and then someone says 'oh wait you aren't in our eyes' and then you considered a kid or 'dwarf adult.' That is not fair."

"I believe that it is still some sort of planet, but it's just a different type or even something else. If it's not a jovian or terrestrial planet, then it has to be something else or in a group beyond these 2 groups of planets."

"It is too small to be considered a planet. Especially if it doesn't have the size for its orbit."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Can you go over the characteristics of Venus and Mars in comparison to Earth? Especially in regards to whether Venus is more/less geologically active than Earth today." (Yes.)

"Do we have to know the names of the dwarf planets, because that is something I don't have down yet." (Not really, but you should know the criteria that determines whether something should be a dwarf planet (or not).)

"How was Pluto at one point classified as a planet, but then at a later time classified as a dwarf planet? What changed exactly?"

"What do you think Pluto should be classified as?"

"Do you think Pluto should be a planet, disregarding the 'recent' planet requirements?" (No. My philosophy is that life isn't always fair. Deal with it, Pluto.)

"I feel really unprepared for our weekly quizzes. I wish I knew exactly what to study. Too much info to remember sometimes. Practice quizzes don't help, the questions are confusing!" (Let's make sure we meet up after class and/or during office hours and we go over what/how you're studying, as this is going to be very different for different people. But good on worrying about this now.)

"Are we going to have a review day for the midterm?" (Yes, we will.)

"Planets are so fascinating and so interesting to study about. Can we stay in this chapter forever?" (But then we'll never get to studying about the stars, galaxies, the big bang theory, and possibility of extraterrestrial life!)

"Why is it that cow farms are never mentioned as a primary methane contributor?" (Well it has been reported in the media that the cattle industry does make a sizable contribution to the total amount of greenhouse gases introduced into the atmosphere. Not as much as fossil fuels, though, but still significant.)

20170925

Physics quiz question: kinetic friction force on sliding suitcase

Physics 205A Quiz 3, fall semester 2014
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 4.85

A force of 10 N is applied to the left on a suitcase that is already sliding to the right, such that it slows down. The floor is not frictionless. If the magnitude of the applied force is slightly increased to 11 N such that the suitcase will slow down at a faster rate while still moving to the right, the magnitude of the kinetic friction force on the suitcase will:
(A) increase.
(B) remain the same.
(C) decrease.
(D) (Not enough information is given.)

Correct answer (highlight to unhide): (B)

The kinetic friction force of the floor on suitcase points to the left, against the direction of motion, and has a magnitude of:

fk = μk·N,

where μk is the kinetic friction coefficient, a property of the suitcase and the floor, and is a constant; while N is the magnitude of the normal force of the floor on the suitcase, which by Newton's first law is equal to the magnitude of the weight force of Earth on the suitcase, also a constant. Thus increasing the applied force on the suitcase will not change the magnitude of the kinetic friction force on the suitcase, as long as it has already been "unstuck" and is moving.

Sections 70854, 70855, 73320
Exam code: quiz03fkfs
(A) : 20 students
(B) : 36 students
(C) : 16 students
(D) : 0 students

Success level: 50%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.57

Online reading assignment: applications of Newton's laws (friction)

Physics 205A, fall semester 2017
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 on applications of Newton's laws (emphasizing static and kinetic friction).


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.
"The coefficient of static friction is a ratio of the maximum static frictional force over the normal force. Therefore in order to find the maximum static frictional force you must multiply the coefficient of static friction by the normal force. The equation is the same when finding the kinetic frictional force just using the coefficient of kinetic friction."

"Static frictional force is the force required for an object to move from rest and is always greater than kinetic friction. Kinetic friction opposes an object's sliding motion on a surface while it is in motion. Newton's first law applies to objects at rest on a surface until it is pushed or pulled enough past the static frictional force then Newton's second law applies."

"Friction is caused by the molecular bonds between two surfaces. There is kinetic friction which is when the force is slowing down to a stop and static friction which is when the force is unable to move. The definitions are easy to understand, but I think applying them to the problems is what is most difficult."

"The two types of friction are static and kinetic. From what I understand, static friction is the force that keeps an object at rest and must be overcome for an object to move along another. On the other hand, kinetic force is the force that slows an object down once in motion."

"I have a fairly strong grasp on how Newton's second law applies to cases with a non-zero net force, and changing motion."

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 was having difficulty with Newton's first law and third law because they seem similar. However, going over different practice problems I feel a little more confident."

"Kinetic friction--I thought I understood it but answering the questions below about the values of fk in different situations left me more confused."

"I'm honestly still getting confused between normal force and net force. I've tried looking at some examples, but singling these two out from each other messes me up."

"It is hard to visualize forces especially if there is a movement. But it will help to learn about free-body diagram to clarify those situations."

"How to apply these concepts of the frictional forces when also incorporating what we have learned with normal forces, weight, etc."

"When kinetic force is in play with normal force and weight force. It's apparent that they're acting in different ways on a object and I can separate them in my head. Figuring out when one is at play or when one affects another is still eluding me."

"I think I understand the concepts well, but I am confused as to the application of the two equations in determining behavior of an object under static or kinetic force."

"Most of the material was understandable."

"Not much was confusing."

What is the meaning of the "normal" in the "normal force?"
"'Normal' means 'perpendicular.'"

"Normal force means the force perpendicular to the object; 'normal' and 'perpendicular' tend to be interchangeable."

"The force that objects in contact exert on each other perpendicular to their planes. I don't know that I can clearly convey the 'normal' part. I just think of it as 'normal' because the objects are just sitting there, exerting this force as long as a they are in contact."

The SI (Système International) units of the static friction coefficient µs and the kinetic friction coefficient µk are:
"Newtons?"

"I have no idea."

"I'm confused."

"Both friction coefficients are dimensionless."

"They both have no units."

"I am a little confused by this. I thought there were no units, but I may have misunderstood."

Identify the magnitude of the static friction force fs for each of the following situations of a box that is initially stationary on a horizontal floor. (Only correct responses shown.)
No external horizontal forces applied to it, so it remains stuck to the floor:
fs = 0. [74%]

An external horizontal force applied to it, but still remains stuck to the floor:
fs = some value between 0 and µs·N. [72%]

An external horizontal force applied to it, at the threshold of nearly becoming unstuck:
fs = µs·N. [64%]

Identify the magnitude of the kinetic friction force fk for each of the following situations of a box that is already sliding across a horizontal floor. (Only correct responses shown.)
No external horizontal forces applied on it, so it slows down:
fk = µk·N. [27%]

An external horizontal force applied in the forward direction, but not enough to keep the box going so it still gradually slows down:
fk = µk·N. [20%]

An external horizontal force applied in the forward direction, just enough to keep the box going at a constant speed:
fk = µk·N. [41%]

An external horizontal force applied in the forward direction, enough to gradually increase the speed of the box:
fk = µk·N. [48%]

An external horizontal force applied in the backwards direction, such that the box slows down:
fk = µk·N. [27%]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Need some clarification on this, mostly on kinetic friction."

"I'm gonna need some review of this in lecture format please!! :("

"I kind of find putting all the laws and everything together a bit confusing. It just seems there's not much lecture in class."

"I think the problem I have is applying these concepts to problem solving. I believe it's just gonna take a lot of practice so please continue with the examples in class."

"Kinetic friction examples would be awesome."

"Newton's third law is used with a force between two interacting objects. Newton's first law is for objects at rest (or constant velocity). I would like to see more Newton's second law examples."

"I would appreciate overview in class of concepts rather than just worksheets on them. I know you say that it is proven that lectures aren't efficient but maybe you could meet students in the middle with some brief lecturing." (I can't really meet everyone in the middle, because everyone needs different things. At least with getting feedback from these reading assignments I can make an informed decision on what/how to cover things in class, whether it is by lecturing (especially today on how static and kinetic friction behave differently), worksheets (so you can get immediate feedback on applying what you just learned), and/or worked-out examples (by me on the whiteboards, or turned in by you at the end of class). But if you are still not getting what you specifically and individually need during class time, then you need to be proactive and ask me question in person or by e-mail, come to my office hours, or go to the tutoring center.)

"If something slides across a smooth surface with some kinetic friction and then continues onto a rougher surface, how does this change the kinetic friction?" (Different materials, different μk coefficients; so the amount of kinetic friction force will change.)

"What is something that can slow an object down but not be considered kinetic friction?" (Drag (air resistance)? Like when a parachute is deployed?)

"These questions seem like trick questions but I'm not sure." (They're meant to make you think. Or trick you into making you think.)

"What instrument can measure the friction coefficient?" (Not directly, but you can measure the friction force by pulling on it with a force sensor, and know the mass of the object (so you can calculate its weight, which is equal to the normal force by Newton's first law), then you can set your experimental friction force value equal to μs·N, and solve for the coefficient. Which is pretty much what you'll be doing in lab next week.)

"Physics is interesting but also very confusing."

"Does Newton's third law apply to static friction? Say an object is not moving yet even when an external applied the force is acting on it to try to make it move. So is there a reaction force that exerts a resisting opposite reaction force?" (Hold on, we're going to need to dig pretty deep to answer this question. This stationary object will have two horizontal forces acting on it: an external applied force (say, you pushing it to the right), and the static friction force that opposes the attempted unsticking (which would make it point to the left). Since the object is still stationary, these two forces are opposite in direction and equal and magnitude, but they would not be related via Newton's third law (as they are two different types of forces: the "applied force" would be a normal contact force (if you are pushing on the side of the object), and the static friction force would be a, well, friction contact force. However, the applied normal contact force of you on the side of the object (directed to the right) would be the third law pair of the normal contact force of the side of the object exerted on you (directed to the left). Also the static friction force of the floor on the object (directed to the left) would be the third law pair of the static friction force of the object on the floor (directed to the right). You should verify that all these third law pairs satisfy the "POF-OST-ITO" checklist, while the first law pair mentioned earlier does not.)

20170923

Astronomy quiz question: planet(s) visible at sunrise?

Astronomy 210 Quiz 2, fall semester 2017
Cuesta College, San Luis Obispo, CA

The locations of Earth, Mars, and Jupiter are shown in the diagram below (not to scale, and orbits have been simplified as circles instead of ellipses).


Which planet(s) will be visible at sunrise?
(A) Mars.
(B) Jupiter.
(C) (Both of the above choices.)
(D) (Neither of the above choices.)

Correct answer (highlight to unhide): (B)

If a line is drawn from Earth to the sun, the observer at sunrise (6 AM) is located perpendicular to that line. Since Mars is below that horizon line, it would not be visible at that time; while Jupiter is above that horizon line, it would be visible low over the east horizon at that time.


Section 70158
Exam code: quiz02Sdi3
(A) : 7 students
(B) : 34 students
(C) : 3 students
(D) : 0 students

Success level: 78% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.69

Astronomy quiz question: Mars visible at sunset?

Astronomy 210 Quiz 2, fall semester 2017
Cuesta College, San Luis Obispo, CA

Tthe locations of Venus, Earth and Mars are shown in the diagram below (not to scale, and orbits have been simplified as circles instead of ellipses).


At sunset, Mars will be visible:
(A) low over the east horizon.
(B) somewhere high up in the sky.
(C) low over the west horizon.
(D) not visible in the sky.

Correct answer (highlight to unhide): (C)

If a line is drawn from Earth to the sun, the observer at sunset (6 PM) is located perpendicular to that line. Since Mars is above that horizon line, it will be visible at that time, and would be located low over the west horizon. (Since Venus is below that horizon line, it would not be visible at sunset.)


Section 70160
Exam code: quiz02NoL4
(A) : 7 students
(B) : 3 students
(C) : 15 students
(D) : 4 students

Success level: 54% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.64

20170922

Physics quiz question: Tesla Model X P100D drag race acceleration

Physics 205A Quiz 2, fall semester 2017
Cuesta College, San Luis Obispo, CA

"Tesla Model X P100D Ludicrous..."
DragTimes
youtu.be/_NnNEuxqoPo

A Tesla Model X P100D took 10.947 s to travel 402 m, speeding up with constant acceleration after starting from rest. Assume that car traveled along a straight horizontal line, and that the acceleration was always pointed in the same direction as the velocity. The magnitude of the acceleration of the car was:
(A) 3.4 m/s2.
(B) 6.7 m/s2.
(C) 37 m/s2.
(D) 73 m/s2.

[*] dragtimes.com/Tesla-Model-X-Timeslip-29390.html.

Correct answer (highlight to unhide): (B)

The following quantities are given (or assumed to be known):

(x0 = 0 m),
(t0 = 0 s),
x = +402 m,
t = 10.947 s,
v0x = 0 m/s.

So in the equations for constant (average) acceleration motion in the horizontal direction, the following quantities are unknown, or are to be explicitly solved for:

vx = v0x + ax·t,

x = (1/2)·(vx + v0xt,

x = v0x·t + (1/2)·ax·(t)2,

vx2 = v0x2 + 2·ax·x.

With the unknown quantity ax to be solved for appearing in the third equation, with all other quantities given (or assumed to be known), then:

x = v0x·t + (1/2)·ax·(t)2,

+402 m = (0 m/s)·(10.947 s) + (1/2)·ax·(10.947 s)2,

+402 m = 0 + ax·(59.9184045 s2),

(+402 m)/(59.9184045 s2) = ax = +6.7091239053 m/s2,

which to two significant figures is +6.7 m/s2.

(Response (A) is x/(t2); response (C) is x/t; response (D) is 2·x/t.)

Sections 70854, 70855
Exam code: quiz02BjRn
(A) : 5 students
(B) : 40 students
(C) : 4 students
(D) : 6 students

Success level: 73%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.64

Physics quiz question: comparing distances traveled

Physics 205A Quiz 2, fall semester 2017
Cuesta College, San Luis Obispo, CA

The x(t) graph of a Physics 205A student walking along a straight line is shown at right. The student started at x = 0 at t = 0. The student walks the greatest distance during the time interval(s):
(A) 0 ≤ t ≤ 3 s.
(B) 3 s ≤ t ≤ 7 s.
(C) 7 s ≤ t ≤ 10 s.
(D) (There is a tie.)

Correct answer (highlight to unhide): (D)

The positions of the student at different times can be immediately read off of this position versus time graph.

At t = 0, the student is located at x = 0 (this is also given in the statement of the problem). At t = 3 s, the student is then located at x = –2 m, such that the student traveled 2 m (in the negative direction) during the 0 ≤ t ≤ 3 s time interval.

At t = 3 s, the student is located at x = –2 m. At t = 7 s, the student is then located at x = –1 m, such that the student traveled 1 m (in the positive direction) during the 3 s ≤ t ≤ 7 s time interval.

At t = 7 s, the student is located at x = –1 m. At t = 10 s, the student is then located at x = –3 m, such that the student traveled 2 m (in the negative direction) during the 7 s ≤ t ≤ 10 s time interval.

Since the student traveled 1 m during the 3 s ≤ t ≤ 7 s time interval, but traveled 2 m during both the 0 ≤ t ≤ 3 s and the 7 s ≤ t ≤ 10 s time intervals, the most correct response is (D).

Sections 70854, 70855
Exam code: quiz02BjRn
(A) : 1 student
(B) : 19 students
(C) : 3 students
(D) : 32 students

Success level: 58%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.74

Astronomy current events question: testing black hole models

Astronomy 210L, fall semester 2017
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!)
Neal Singer, "Black Hole Models Contradicted by Hands-on Tests at Sandia's Z Machine" (August 28, 2017)
share-ng.sandia.gov/news/resources/news_releases/black_hole/
Results from Sandia National Laboratories' Z machine tested predictions of how x-rays should be emitted from:
(A) the northern lights.
(B) matter falling into black holes.
(C) supernovae explosions.
(D) dark matter.
(E) fusion reactions within stars.

Correct answer: (B)

Student responses
Sections 70178, 70186
(A) : 0 students
(B) : 31 students
(C) : 9 students
(D) : 5 students
(E) : 1 student

Astronomy current events question: TRAPPIST-1 planet water content

Astronomy 210L, fall semester 2017
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!)
Vincent Bourrier, Julien de Wit, and Mathias Jäger, "Hubble Delivers First Hints of Possible Water Content of TRAPPIST-1 Planets" (August 31, 2017)
spacetelescope.org/news/heic1713/
Planets orbiting dwarf star TRAPPIST-1 may retain some water, based on Hubble Space Telescope observations of:
(A) reflective ice crystals.
(B) escaping water plumes.
(C) gamma ray emissions.
(D) gravitational wave fluctuations.
(E) absorbed ultraviolet light.

Correct answer: (E)

Student responses
Sections 70178, 70186
(A) : 8 students
(B) : 14 students
(C) : 7 students
(D) : 2 students
(E) : 15 students

Astronomy current events question: recovery of 1437 A.D. nova location

Astronomy 210L, fall semester 2017
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!)
American Museum of Natural History press release, "Scientists Recover Nova First Spotted 600 Years Ago by Korean Astrologers" (August 30, 2017)
amnh.org/about-the-museum/press-center/scientists-recover-nova-first-spotted-600-years-ago
The exact position of a nova explosion that occurred 600 years ago was located by comparing present-day images with:
(A) old photographic plates.
(B) gravitational wave fluctuations.
(C) absorbed ultraviolet light.
(D) computer simulations.
(E) gamma ray emissions.

Correct answer: (A)

Student responses
Sections 70178, 70186
(A) : 21 students
(B) : 3 students
(C) : 10 students
(D) : 8 students
(E) : 6 students

Physics quiz question: Hafþór Björnsson world record one-handed vertical toss

Physics 205A Quiz 2, fall semester 2017
Cuesta College, San Luis Obispo, CA

"2017 Rogue Record Breaker - Hafthor Bjornsson's 19' 7" Weight For Height"
RogueFitness
youtu.be/k8cWd933WoM

In 2017, Game of Thrones actor Hafþór Björnsson tossed one-handed a 56 lb weight upwards to a world record maximum height. Video analysis shows that from the moment it left his hand (with an initial upwards speed), the weight took 0.92 s to reach its highest height[*]. Neglect air resistance. Choose up to be the +y direction. At the moment it left his hand, the weight had an initial speed of:
(A) 4.1 m/s.
(B) 9.0 m/s.
(C) 11 m/s.
(D) 18 m/s.

[*] instagram.com/p/BRUStRIgPfX/.

Correct answer (highlight to unhide): (B)

The following quantities are given (or assumed to be known):

(t0 = 0 s),
(y0 = 0 m),
vy = 0 m/s (momentarily stationary at its highest point),
t = 0.92 s (time when at its highest point),
ay = –9.80 m/s2.

So in the equations for constant acceleration motion in the vertical direction, the following quantities are unknown, or are to be explicitly solved for:

vy = v0y + ay·t,

y = (1/2)·(vy + v0yt,

y = v0y·t + (1/2)·ay·(t)2,

vy2 = v0y2 + 2·ay·y.

With the unknown quantity v0y to be solved for appearing as the only unknown in just the first equation above, with all other quantities given (or assumed to be known), then:

vy = v0y + ay·t,

0 m/s = v0y + (–9.80 m/s2)·(0.92 s),

v0y = (9.80 m/s2)·(0.92 s) = +9.016 m/s,

or to two significant figures, the initial speed of the weight was 9.0 m/s (in the upwards direction).

(Response (A) is (1/2)·ay/t2; response (C) is ay/t; response (D) is 2ay·t.)

Sections 70854, 70855
Exam code: quiz02BjRn
(A) : 5 students
(B) : 39 students
(C) : 11 students
(D) : 0 students

Success level: 71%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.42

20170921

Astronomy quiz archive: eclipses/history of astronomy

Astronomy 210 Quiz 2, fall semester 2017
Cuesta College, San Luis Obispo, CA

Section 70158, version 1
Exam code: quiz02Sdi3


Section 70158
0- 8.0 :   ** [low = 3.0]
8.5-16.0 :   ********
16.5-24.0 :   ****************** [mean = 22.0 +/- 7.8]
24.5-32.0 :   ***********
32.5-40.0 :   ***** [high = 36.5]


Section 70160, version 1
Exam code: quiz02NoL4


Section 70160
0- 8.0 :   * [low = 6.5]
8.5-16.0 :   ******
16.5-24.0 :   *********** [mean = 23.3 +/- 8.4]
24.5-32.0 :   ******
32.5-40.0 :   ***** [high = 40.0]

20170920

Online reading assignment: atmosphere problems, Earth, the moon, Mercury (SLO campus)

Astronomy 210, spring semester 2017
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 problems caused by the atmosphere for telescope observing, Earth, and the impacted worlds: the moon, and Mercury.

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.
"Light pollution is the reason why in the movies people go star gazing outside of the city like in the top of a mountain. I never knew why but after doing the reading now I know it's because both light from man-made or natural sources will be reflected by particles in the atmosphere and interfere with light from the faint stars, washing them out."

"Finding out why stars 'twinkle' because I didn't know why before I read the section."

"That the sky is basically an ocean of air, and what you see is easily distorted."

"How much we see in the sky is washed out by man-made light and natural light (the moon)."

"Thought it was really cool how they have now put telescopes on aircraft. It's just something that I wouldn't of thought of; however, it's for the most part pretty effective and more cost effective."

"Something that interested me was the turkey vs. Cornish hen effect. It interested me because it helped me understand the concept of the cores of planets."

"How most of the carbon dioxide is entered into Earth's atmosphere through volcanos, and absorbed through the ocean. Like I thought it was entered from the ocean and absorbed by plants."

"I had no idea Mercury and our moon looked so much alike! For this reason I thought this was the most interesting thing."

"The theory about the moon and Mercury's core is very interesting. I've never thought of planets colliding and changing the sizes of the cores on the planets and moon."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"I can't seem to grasp the concept of how the telescopes work and how the magnification, light-gathering, and resolving powers differently affect the way you can view things in the sky."

"The different powers of telescopes. I'm not a very visual person so it was hard for me to imagine how light enters and reflects to create and amplify certain images."

"I'm having trouble understanding atmospheric turbulence. Although the example of humans living at the 'bottom of an ocean of air' made sense, I can't figure out how to quite understand how it works with twinkling."

"Turbulence was a little confusing. I'm not sure how the Keck Telescopes work using the active optics."

"The large-impact hypothesis. I was just kind of lost about the whole collision thing and how it formed what exactly."

"I'm not confident in answering 'what is oldest/youngest' with regards to our moon and Mercury's craters. I've read the chapters, some more than once, and read the slides but for some reason I can't figure this out."

A large modern optical telescope in outer space would have images with better __________ than a comparable ground-based telescope.
brightness.   * [1]
resolution.   ************* [13]
magnification.   [0]
(None of the above choices.)   * [1]
(Two of the above choices.)   ******** [8]
(All of the above choices.)   ********* [9]
(Unsure/guessing/lost/help!)   **** [4]

Stars to appear to "twinkle" in the night sky because of...
"Atmospheric turbulence causes stars in the sky to look distorted or "twinkle." It stirs up the air making it hard to have a clear image of what's in the sky. This is why getting as high up as possible for viewing is important so the air is thin and you can get less disturbance from the atmosphere."

"Atmospheric turbulence in the 'ocean of air.'"

Identify how carbon dioxide enters and how it is taken out of Earth's atmosphere.
(Only correct responses shown.)
Enters atmosphere from: volcanoes [67%]
Taken out of atmosphere by: oceans [61%]

Identify the oldest (longest ago) to the youngest (most recent) features on the moon.
(Only correct responses shown.)
Craters partially filled in with flat lava plains: oldest (formed longest ago) [36%]
Flat lava plains: middle [28%]
Craters on top of flat lava plains: youngest (formed most recently) [53%]

Identify the oldest (longest ago) to the youngest (most recent) features on Mercury.
(Only correct responses shown.)
Large crater basins: oldest (formed longest ago) [58%]
Lava-filled lowlands: middle [42%]
Long curving ridges: youngest (formed most recently) [47%]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Why doesn't air turbulence cause planets to twinkle? (The planets do twinkle, but it's not as noticeable. The stars are basically points of light, and 'twinkling' a point of light will make it noticeably distorted. Planets are large enough to be a small disk of light, and 'twinkling' a disk would only distort its edges, so the effect on its brightness is not as noticeable.)

"There was a lot of material covered over the presentation previews and textbook reading so some general clarifications would be nice."

"Could you please go over the relative ages of the moon's and Mercury's surfaces?"

"Why is the core of Earth hotter than Mercury's core?" (That's the turkey vs. Cornish hen effect.)

"Why is it that terrestrial planets are closer to the sun, while jovian planets are farther away?" (During the formation of the planets around the young sun, the inner planets formed closer in where it was hotter, and the outer planets formed farther away where it was cooler. Because of this, a lot of ices and gases were vaporized off of the terrestrial planets as they formed, so they are primarily rocky, while in the outer parts of the solar system it was cool enough for ices and gases to form around rocky cores and make the jovian "gas giant" planets.)

"Do you own a telescope?" (No; but I get to use Cuesta College's telescopes whenever I want to.)

"Where was the Hubble Space Telescope when it sent its last transmission?" (It's still working, last I checked.)

"Are you a Star Wars fan?" (Yes, but the original, non-special edition episodes IV-VI only. The most recent two sequels were okay, though.)

"What got you into swing dancing?" (I need to get out and get a life. Oh, and I met Mrs. P-dog from going out swing dancing.)

Online reading assignment: Newton's third law

Physics 205A, fall semester 2017
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 Newton's third law.


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.
"Newton's first law says for objects that stay immobile or keep moving on a straight line, there is zero net force. Newton's second law says that an object will accelerate in the direction of a non-zero force. Newton's third law says that for every action there is a reaction force."

"Newton's third law focuses on the relationships of objects and the forces that they apply to one another. If there are two pairs of objects of the same type explicitly interacting with one another, Newton's third law applies."

"Newton's third law relates the interactions of a force between two objects. If there exists a pair of two opposite forces, they are the same type of force, and there are explicitly two objects in the situation, then N3 applies."

"Newton's third law is that all forces occur in pairs and there isn't such thing as an isolated force, existing by itself. In other words, each force involves two objects interacting with one another."

"For Newton's third law to apply it has to be a 'yes' to all three parts of the POF-OST-ITO checklist. If even one part is a 'no,' then the third law cannot apply."

"An interaction always involves two objects, each exerting a force on each other. If there aren't two objects involved, then there is no interaction."

"I will understand in class."

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.
"Net forces on stationary objects is confusing, but it's handy knowing that in the end it all needs to end up as zero. Also like in the homework question, if an object is decelerating, then the net force is opposite the direction of travel, makes sense but stumps me at first."

"Some ways of describing the forces on an object can be confusing at times because it's not always stated very clearly in problems."

"Determining the differences between forces that are equal in magnitude but opposite in direction from Newton's first or third law."

"How to apply Newton's third law to most situations and also kind of confused on the normal force and what that means."

"I get how to set up the third law, but knowing what forces are being applied to an object can be challenging. In addition, finding the overall direction of the net force is proving difficult."

"Newton's laws don't seem confusing, but I could probably use some more practice applying them to problems."

"How to implement POF-OST-ITO."

"The POF-OST-ITO checklist and its application to Newton's third law. Going over it in class will be beneficial."

"Everything seems pretty straightforward."

Consider two categories of motion: (1) Velocity that is constant and unchanging. (2) Velocity that is changing. Discuss whether or not there would be a third category of motion not already covered under these two categories.
"Those should cover all the categories."

"I don't think there would be a third category. (1) covers zero velocity, which doesn't leave any other possibilities."

"No, there is only changing and unchanging motion."

"Since Newton's third law does not necessarily have to do with motion, just about forces regardless of the motion, I don't think there is a third category."

"Velocity that has constant speed but is changing in direction?"


According to Newton's first law, the normal force of the person's head on the stack of books is equal in magnitude and opposite in direction to the:
normal force of the stack of books on the person's head.   *************** [15]
weight force of Earth on the stack of books.   ******************* [19]
(Both of the above choices.)   ******** [8]
(Neither of the above choices.)   * [1]
(Unsure/guessing/lost/help!)   ** [2]


According to Newton's third law, the normal force of the person's head on the stack of books is equal in magnitude and opposite in direction to the:
normal force of the stack of books on the person's head.   ********************* [21]
weight force of Earth on the stack of books.   [11]
(Both of the above choices.)   ***** [5]
(Neither of the above choices.)   * [1]
(Unsure/guessing/lost/help!)   ******* [7]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Can there be three equal, opposite forces? Is that possible?" (Um, no.)

"Class is ramping up, hoping for a little more in-class discussion and a lot more variety in the in-class problems."

Some clarification on normal force would be nice."

"Could we get some more clarifications on Newton's third law?"

"Newton's third law is still a bit confusing compared to the first two laws for me. Is there a simple way to look at it compared to the first two?"

"I would like more example problems."

"More N3 examples please!"

"Third law of motion seems important."

"Physics is fun because it can be related to something in real life and applied a lot easier than other subjects."

"What do you believe is the best way to study for the quizzes?" (That is going to be very different for different students. But at least you should be able to gauge from the quizzes and homework problems from previous semesters where your difficulties are; if it seems like this is everything, then let's have a conversation in office hours, or at the very least via e-mail.)

"What made you use the flipped classroom style of teaching?" (Physics education research shows that traditional lecture is the least effective method of teaching, in terms of what students retain after the end of class. Note that we don't have a completely "flipped class" (all homework in class, all video learning outside of class), but one that is "lightly flipped" with various research-validated learning activities in class, in lab, and outside of class . #bywhatevermeansnecessary)

"Do you watch Game of Thrones? Please follow up in class. Thank you." (Mrs. P-dog and I still need to catch up from halfway through season five, but we'll get there. #thenightisdarkandfullofterrors)

20170919

Physics quiz archive: kinematics, free fall

Physics 205A Quiz 2, fall semester 2017
Cuesta College, San Luis Obispo, CA
Sections 70854, 70855 version 1
Exam code: quiz02BjRn



Sections 70854, 70855 results
0- 6 :   * [low = 6]
7-12 :   ******
13-18 :   ************
19-24 :   **************** [mean = 22.0 +/- 6.5]
25-30 :   ********************* [high = 30]

Online reading assignment: atmosphere problems, Earth, the moon, Mercury (NC campus)

Astronomy 210, fall semester 2017
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 problems caused by the atmosphere for telescope observing, Earth, and the impacted worlds: the moon, and Mercury.

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 massive planets have hotter cores than less massive planets. Earth has a hotter core than other terrestrial planets because it is the most massive."

"The fact that Earth is not dying as much as some other planets and the moon. The heat of the cores has a lot to do with this apparently. I had no idea that that was the case."

"The hypotheses for the origin of Earth's moon because the moon is an object which is frequently seen and to know how it came to be is something I find interesting."

"How what we can see is such a small portion of the electromagnetic spectrum."

"Why stars twinkle--I originally thought that the twinkle in stars had something to do with their gases; I did not think it was something as basic as our atmosphere's turbulence."

"That we live at the bottom of an ocean of air. Never thought about it like that."

"The electromagnetic spectrum is interesting to me because it is fascinating how our world is permeated with waves invisible to the naked eye. The most frightening of those waves being gamma rays, seeing as gamma ray bursts are emitted whenever a star explodes. and these bursts can wipe out a planet!"

"That the moon looks very similar to Mercury, while one is a planet and the other is a moon. Why do they look so similar, if they very different?"

"The large impact theory, because I feel like a massive collision could not produce something like the moon."

"How the ocean takes carbon dioxide out of the atmosphere."

"This was probably the most interesting section to me so far, especially with all the really dope time lapse videos from ISS and also the Keck telescope. Other than that it also really cool to see the theories we have on the formation of Earth and also how Earth differs from our neighboring planets and the moon."

"I knew Earth was special because it has a lot of water, but I never really realized how much water it has and how little water other planets with water have."

"That Mars and Venus were once different planets with different characteristics such as having water and different atmosphere. I am also glad Earth got its secondary atmosphere otherwise we wouldnt be here."

"How Venus is essentially a 'greenhouse effect gone wrong,' and how Earth is at a high risk for following suit."

"Adaptive optics, because it shows how important resolving power is when looking through a telescope."

"The 'Keck in Motion' video was super-fascinating! It was crazy to me that everything was so precise and complicated, and it made me question what is so important that billions of dollars should be spent on such projects? Regardless, that was a cool video!"

"I always thought that the different shades on the moon were just shadows. I had no idea the mare is dark because of dark lava also."

"How global warming is affecting Earth currently."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"Trying to wrap my head around how mere wind can distort the image in a telescope."

"Adaptive optics."

"How exactly Earth's core heat would benefit life forms. Obviously if ours was super-cold nothing would survive, but I feel like opposite should be true as well. Maybe ours is just right though."

"The greenhouse effect."

"I could use a little more discussion on the greenhouse effect, specifically how the oceans are responsible for controlling the amount in our atmosphere. I didn't quite follow the soda pop explanation."

"What was the reason for why Mercury's core is big for a planet of its size?"

"Determining features of the moon and Mercury that are or older or newer."

A large modern optical telescope in outer space would have images with better __________ than a comparable ground-based telescope.
brightness.   ** [2]
resolution.   ******* [7]
magnification.   [0]
(None of the above choices.)   * [1]
(Two of the above choices.)   ****** [6]
(All of the above choices.)   ********** [10]
(Unsure/guessing/lost/help!)   * [1]

Stars to appear to "twinkle" in the night sky because of...
"We are viewing them through layers of turbulent air in the Earth's atmosphere."

"The stars twinkle in the night because of turbulence in the atmosphere, kind of like looking at the sky from underwater."

Identify how carbon dioxide enters and how it is taken out of Earth's atmosphere.
(Only correct responses shown.)
Enters atmosphere from: volcanoes [59%]
Taken out of atmosphere by: oceans [67%]

Identify the oldest (longest ago) to the youngest (most recent) features on the moon.
(Only correct responses shown.)
Craters partially filled in with flat lava plains: oldest (formed longest ago) [44%]
Flat lava plains: middle [37%]
Craters on top of flat lava plains: youngest (formed most recently) [15%]

Identify the oldest (longest ago) to the youngest (most recent) features on Mercury.
(Only correct responses shown.)
Large crater basins: oldest (formed longest ago) [52%]
Lava-filled lowlands: middle [52%]
Long curving ridges: youngest (formed most recently) [59%]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"I never knew turbulence in the sky cause stars to appear as if they are 'twinkling.'"

"It would be nice if we would be able to have the answers to the worksheet packets so that we can know whether we are studying the correct answers." (As a matter of policy the answers to the worksheet questions are not published. However, you are free to ask questions while I'm circulating during group work in class, come in to office hours, or e-mail me your answers, and I can "grade" them for you. Just don't wait until the last-minute to do so.)

"How can the adaptive optics tell the shape of something that scientists do not know the shape of?" (Without turbulence, stars are supposed to be perfect points of light; so if you can manage to "undistort" light affected by turbulence to get stars back to looking like points, then anything else in that part of the sky like planets, nebulae, and galaxies will then be undistorted.)

"Do you believe in the big bang theory? If not, what is your belief on the formation of our planet and the other planets in our solar system?" (I understand the evidence supporting what we know about the big bang theory; that pretty much sums up how I feel about things I understand vs. things I believe in (but don't understand).)

"Why is it that certain types of electromagnetic radiation cannot make it past the Earth's atmosphere? Does that mean the higher we go in space the more spectrum we would be able to see?" ((1) Atoms and molecules in the atmosphere are really good at absorbing or scattering gamma rays, x-rays, and some ultraviolet and infrared light, but atoms and molecules are for the most part relatively more "transparent" to visible light, letting it pass through; so (2) yes.)

"It was interesting to learn that the ocean absorbs carbon dioxide. The ocean is already so great, but it's cool to know it also does that too."

"Can you go over the youngest and oldest features on the moon and Mercury?"

"I'm loving this class so far, I'm always eager to start this class's homework first! Can't wait to learn more next class. :D"

"I don't have a question. Thank you."

"Why do you wear your watch upside-down?" (I've cracked a lot of watch face crystals, so wearing it facing "in" (or "upside-down") seems to protect it from my accident-prone everyday activities. #umopapisdn)