20150930

Physics quiz archive: vectors, projectile motion, forces

Physics 205A Quiz 3, fall semester 2015
Cuesta College, San Luis Obispo, CA
Sections 70854, 70855, 73320, version 1
Exam code: quiz03re3T



Sections 70854, 70855, 73320 results
0- 6 :   * [low = 6]
7-12 :   *
13-18 :   *******************
19-24 :   ****************************** [mean = 22.4 +/- 4.9]
25-30 :   ********************** [high = 30]

Online reading assignment: quantum leaps, sun's outer layers (SLO campus)

Astronomy 210, fall semester 2015
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 quantum leaps, and the sun's outer layers.


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.
"Electrons have the correct energies to be able to jump up to orbits in order jump down and give off photons."

"That sunspots come in pairs. I never knew that! It is interesting because this happens due to temporary magnetic regions that they have."

"Everything is interesting since I am not too familiar with this section."

"How Egyptians viewed/explained the sun as having wings and fire-spitting cobras. It was like a mini-history lesson within the astronomy material."

"How hot the sun is. Like, I knew it was hot, but wow."

"That sunspots aren't hotter than the rest of the sun's surface."

"I really enjoyed the presentation on quantum mechanics. Until I read about it in the book, I assumed that knowledge of quantum mechanics was outside of my scope of understanding. The movement of electrons from one orbit to the next was very cool."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"Sunspots being temporary magnetic regions on the sun."

"Chemistry!"

"Photons and electrons to be particularly confusing. Mostly because I haven't taken chemistry in quite a few years."

"Chemistry is almost as dry of reading as history! But not too bad, just takes a little time."

"The analogy between a lightbulb filament and sunspots."

"Electrons and how they move orbits by photons. It's all a little wordy to understand, maybe we can dumb it down in class a little, with a flow chart or something :)"

"Nothing was too confusing to me."

An electron in an atom must emit a photon when it jumps from a __________ energy orbital to a __________ energy orbital.
lower; higher.  ****** [6]
higher; lower.  ******************************* [31]
(Both of the above choices.)  * [1]
(Unsure/guessing/lost/help!)  * [1]

An electron in an atom must absorb a photon when it jumps from a __________ energy orbital to a __________ energy orbital.
lower; higher.  ******************************* [31]
higher; lower.  ******* [7]
(Both of the above choices.)  [0]
(Unsure/guessing/lost/help!)  * [1]

The exterior of the sun, from inner to outermost layers, are the:
(Only correct responses shown.)
inner: photosphere [74%]
middle: chromosphere [79%]
outer: corona [72%]

State your preference regarding miso soup.
Strongly dislike.  [0]
Dislike.  [0]
Neutral.  ****** [11]
Like  ******* [7]
Strongly like.  ******************** [20]
(I don't know what miso soup is.)  * [1]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"If I have only done like 4 homeworks am I failing?" (Then you've only missed two so far, and if you don't miss any more, you'll still get a 100% on the online reading assignment points.)

"Is extra-credit available at some point?" (Yes. Sooner than you think.)

"I'm finding the group work very difficult for learning purposes. It's hard to never have my own paper personally graded because that's the way I learn what mistakes I need to fix. Next class I'll try printing out the handouts/in-class assignments and using them in class to see if that helps." (Yes, many students do just that.)

"I LOVE MISO SOUP THANK YOU FOR ASKING." (You're welcome.)

"Miso is the best when mixed with rice and Sriracha. Mmmm...home cookin'." (#dayum)

"The miso soup I usually get is stagnant, only when I stir the soup then I see movement." (Sounds like someone needs to order piping hot miso for homework.)

Online reading assignment: energy conservation

Physics 205A, fall semester 2015
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 energy conservation.


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.
"I did not understand most of it."

"The weight force of Earth on an object is a conservative force, as when this gravitational force does work against an object, removing its energy, it is able to store this energy, and return it to the object by later doing work on the object, therefore we talk about the increases or decreases in gravitational potential energy."

"The concept that energy cannot be created nor destroyed. It is only stored and transferred into different forms."

"Elastic potential energy: when a rubber band is stretched, there is a higher energy than when it is relaxed."

"There are conservative and nonconservative forces that can act on things. Elastic and gravitational potential energies are conservative. These can be used for mechanical or useful energy."

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 am trying to grasp all of these concepts I'm not really aware of what I need to work on."

"I found most of it confusing."

"How to tell if gravitational potential energy is increasing or decreasing."

"Just please lecture on the important points in this section. Nothing is too confusing a long as it is properly explained."

"I don't fully understand about gravity being a conservative force, and where or how it stores energy."

For the woman moving upwards after being catapulted, her translational kinetic energy __________ while her gravitational potential energy __________.
decreases; increases.   ************************************ [36]
increases; decreases.   ***************** [17]
(Unsure/lost/guessing/help!)   ***** [5]

For the ball bearing being launched by the slingshot, its translational kinetic energy __________ while the elastic potential energy of the slingshot bands __________.
decreases; increases.   ****** [6]
increases; decreases.   ************************************************ [48]
(Unsure/lost/guessing/help!)   **** [4]

For the woman falling off the building starting from the edge of the roof to just before reaching her lowest point of descent, indicate the changes in each her of energy forms. (Only correct responses shown.)
Translational kinetic energy: increases. [65%]
Gravitational potential energy: decreases. [64%]
Elastic potential energy (of the bungee cords): increases. [59%]

For the woman falling off the building starting from the edge of the roof to just before reaching her lowest point of descent, the energy form that experienced the greatest amount of change (increase or decrease) was:
her translational kinetic energy.   ********** [10]
her gravitational potential energy.   **************************** [28]
the elastic potential energy of the bungee cords.   ******** [8]
(Unsure/lost/guessing/help!)   ************ [12]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Please help. I think 'unsure/lost/guessing/help' is the #motto today."

"Gravitational potential energy and elastic potential energy are pretty straightforward."

"I would benefit from more examples of the energy conservation problems."

"Whew--a lot covered in these section, but will be ready to dive in and reinforce tomorrow."

"Uh...I dunno about these. I understand that if one type of energy increases, the others have to decrease to compensate (since energy cannot be created nor destroyed or something like that), but I will definitely need some explanation on these."

20150929

Online reading assignment: quantum leaps, sun's outer layers (NC campus)

Astronomy 210, fall semester 2015
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 quantum leaps, and the sun's outer layers.


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 glowing disk of the sun at sunset is 109 times the diameter of Earth's. It is absolutely amazing to me that there can be things so much bigger than Earth."

"Basically, reading about the sun was pretty interesting. I liked reading about sunspots--had no idea that even existed."

"I it interesting that you referred to miso soup as 'sun-surface soup.'"

"I thought it was mind-boggling to look at an image of the photosphere and the process of granulation and try to imagine that each granule represented was about the size of Texas."

"I've never known much about the sun and now I do and it makes me happy."

"I found it interesting how the ancient Egyptians represented the chromosphere with the sun having wings and cobras spitting fire. Looking at the slide from the presentation I can see how they would see that."

"I think it's crazy how exact electrons have to be when absorbing or releasing photons in order to move from one energy level to the next."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"I've never been very good with chemistry so I still get a little confused whenever it comes to that."

"I got a little bit lost on the section discussing atoms. I think it was just a lot of terminology and I was failing to understand the process behind each term i.e. permitted orbits, quantum jumps, etc."

"I'm still a bit lost on sunspots and how they are compared to magnets and TVs."

"It's hard for me to contemplate the heat of the suns surface because of how hot it supposedly is."

"What I found confusing is how sunspots on the sun's surface are cool, when the sun is so hot. I don't understand how it's caused by the strong magnetic fields."

An electron in an atom must emit a photon when it jumps from a __________ energy orbital to a __________ energy orbital.
lower; higher.  ****** [6]
higher; lower.  ********* [9]
(Both of the above choices.)  *** [3]
(Unsure/guessing/lost/help!)  [0]

An electron in an atom must absorb a photon when it jumps from a __________ energy orbital to a __________ energy orbital.
lower; higher.  ************ [12]
higher; lower.  ***** [5]
(Both of the above choices.)  * [1]
(Unsure/guessing/lost/help!)  [0]

The exterior of the sun, from inner to outermost layers, are the:
(Only correct responses shown.)
inner: photosphere [67%]
middle: chromosphere [72%]
outer: corona [67%]

State your preference regarding miso soup.
Strongly dislike.  [0]
Dislike.  ** [2]
Neutral.  ** [2]
Like  **** [4]
Strongly like.  ******* [7]
(I don't know what miso soup is.)  *** [3]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Did you see the lunar eclipse?" (No, it was cloudy. #fml)

"Many things that we have discussed in class about the other planets around us is from assumptions. What if most of it is wrong?" (Then science is progressing. #themoreyouknow)

"What is miso soup?" (For those of you who don't even know what that is, go and try miso soup for homework.)

"Why the question about miso soup?" (Because, it's delicious. Also, physics.)

"I can read the textbook but I find that when you give a brief overview I suddenly get that 'ah ha' moment." (I live for moments like that.)

20150928

Online reading assignment: work and energy

Physics 205A, fall semester 2015
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 work and energy.


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.
"Even if a force is acting on an object, the work done on that object will be zero if it is not moved. Work is computed using the part of the force acting in the direction of movement."

"Work acting on an object increases its translational kinetic energy and that work acting against it reduces the translational kinetic energy."

"Translational kinetic energy is measured in joules. Work results in the change of translational kinetic energy."

"Work is accomplished by exerting a force over a displacement. Work can be done on or against any mechanical energy form or forms."

"How changes in kinetic energy relates to work, and how forces can do work on an object rather than just result in a net force."

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 honestly feel very good about these concepts, and don't currently don't feel confused on the reading."

"I get this sections and its concepts. What I don't understand is where, and how the work-energy theormen was derived."

"The concept of 'work.' I don't understand the concept of it and how to quantitatively describe 'work.'"

Explain how the SI (Système International) unit for work is related to the SI unit for force.
"The units are related by a ratio of one-to-one."

"They are both joules."

"The unit of work is the unit of force times the unit of distance."

"A newton·meter = joule."

Match the description of the work exerted by these forces for each object. (Only correct responses shown.)
Pushing in the same direction of motion: work done "on" the object (positive work). [88%]
Pushing opposite the direction of motion: work done "against" the object (negative work). [93%]
Pushing 90° sideways to the direction of motion: no work done. [57%]
Pulling such that the angle between the force and motion is an acute angle (between 0° and 90°): work done "on" the object (positive work). [58%]
Pulling such that the angle between the force and motion is an obtuse angle (between 90° and 180°): work done "against" the object (negative work). [52%]

For the catapulted squirrel, the bungee cord force does work __________ the squirrel, which __________ the squirrel's translational kinetic energy.
on; increases.   ********************************************************* [57]
against; decreases.   ********** [10]
(Unsure/lost/guessing/help!)   [0]


For the braking car, the brakes do work __________ the car, which __________ the car's translational kinetic energy.
on; increases.   ***** [5]
against; decreases.   ************************************************************** [62]
(Unsure/lost/guessing/help!)   [0]


For Mrs. P-dog being catapulted, the bungee cords do work __________ Mrs. P-dog, while the weight force does work __________ Mrs. P-dog.
on; on. *** [3]
on; against.   **************************************************** [52]
against; on.   ***** [5]
against; against.   *** [3]
(Unsure/lost/guessing/help!)   **** [4]


For Mrs. P-dog's translational kinetic energy to be increased while being catapulted, the amount of work from the bungee cords must be __________ the amount of work from the weight force.
less than.   * [1]
the same as.   *** [3]
greater than.   ************************************************************** [62]
(Not enough information is given.)   [0]
(Unsure/lost/guessing/help!)   * [1]


Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Was that your squirrel catapult?" (I wish it was. #squadgoals)

"Hmm....I didn't know I had to answer this portion of the reading assignment to get full credit!" (Eh, not really. Unless you left every other free-response part of the reading assignment blank.)

"How do I determine whether the work done on an object is positive or negative just by knowing the angle between the force and displacements on that object?" (We'll cover this briefly at the start of tomorrow's class.)

"This stuff only gets harder." (Really? After the first midterm each of these chapters is more self-contained, and thus does not critically depend on previous chapters. #ymmv)

20150926

Astronomy current events question: Saturn's warmer than expected "A" ring

Astronomy 210L, fall semester 2015
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!)
Preston Dyches, "At Saturn, One of These Rings Is Not Like the Others" (September 2, 2015)
jpl.nasa.gov/news/news.php?feature=4709
Comparison of computer__________ models with data taken by NASA's Cassini spacecraft may explain the warmer than expected temperatures of Saturn's "A" ring.
(A) convection current.
(B) particle composition.
(C) magnetic field.
(D) gravitational.
(E) greenhouse effect.

Correct answer: (B)

Student responses
Sections 70178, 70186
(A) : 2 students
(B) : 20 students
(C) : 3 students
(D) : 2 student
(E) : 3 students

Astronomy current events question: variations in Mercury's rotational speed

Astronomy 210L, fall semester 2015
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!)
Leigh Cooper, "Mercury’s Movements Give Scientists Peek inside the Planet" (September 9, 2015)
blogs.agu.org/geospace/2015/09/09/mercurys-movements-give-scientists-peek-inside-the-planet/
Mercury's core composition and gravitational interactions with the outer planets can be analyzed from __________ data measured by NASA's Messenger spacecraft.
(A) seismic.
(B) rotation rate.
(C) temperature.
(D) polar ice.
(E) magnetic field.

Correct answer: (B)

Student responses
Sections 70178, 70186
(A) : 1 student
(B) : 20 students
(C) : 3 students
(D) : 1 student
(E) : 5 students

Astronomy current events question: comet 67P Churyumov-Gerasimenko's "neck"

Astronomy 210L, fall semester 2015
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!)
Emily Lakdawalla, "How the Duck Got Its Neck: Rapid Temperature Changes from Self-Shadowing May Explain 67P's Unusual Activity and Shape" (September 11, 2015)
planetary.org/blogs/emily-lakdawalla/2015/09110855-how-the-duck-got-its-neck.html
Computer modeling of __________ may explain how comet Churyumov-Gerasimenko's "neck" developed over time.
(A) rapid temperature changes.
(B) random collisions.
(C) rotation rates.
(D) gravitational fields.
(E) seismic instability.

Correct answer: (A)

Student responses
Sections 70178, 70186
(A) : 22 students
(B) : 2 students
(C) : 1 student
(D) : 3 students
(E) : 2 students

20150923

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

Astronomy 210, fall semester 2015
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.
"Venus and Mars can be considered the 'runaway' planets."

"That Pluto isnt a planet anymore. Ive known that for a while but I never knew why it wasn't considered a planet anymore."

"The history of the planets, as I got a better idea of how they compare to Earth."

"Even though Uranus and Neptune have about the same mass, and Neptune is further from the sun, yet Uranus has a colder atmosphere."

"How core heat and sunlight make weather more active and colorful on Jupiter compared to Saturn. "

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"Why was Pluto considered a planet before? It seems weird that they just changed the rules and kicked Pluto out."

"Would really like a better explanation as to why uranus and neptune are so similar and yet look so different."

"The gravy analogy. How the formation of volcanoes can pause and 'sleep.' I'm not sure exactly how this works and if the volcano is in a cooling state or in a resting state."

"Nothing confusing. I'm really looking forward to moving out of our solar system, but I understand that we need to know the basics first."

"How gas particles escaped from Mars thus dissipating its atmosphere."

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 [50%]
Geologic activity, today: less than Earth [91%]
Volcanic outgassing, up until now: about the same as Earth [76%]
Heat from the sun: more than Earth [32%]
Amount of atmosphere, today: more than Earth [65%]

Identify the relative amounts of these characteristics for Mars, compared to Earth. (Only correct responses shown.)
Interior core heat, today: less than Earth [82%]
Geologic activity, today: less than Earth [85%]
Volcanic outgassing, up until now: less than Earth [71%]
Heat from the sun: less than Earth [71%]
Amount of atmosphere, today: less than Earth [71%]

Which jovian planet has the coolest interior temperatures?
Jupiter (most massive).   ** [2]
Saturn (most prominent rings).   *** [3]
Uranus (least active weather patterns).   ***************** [17]
Neptune (farthest from the sun).   ************ [12]
(Unsure/guessing/lost/help!)   [0]

I believe Pluto should be a planet.
Strongly disagree.   * [1]
Disagree.   ******** [8]
Neutral.   *************** [15]
Agree.   ******* [7]
Strongly Agree.   *** [3]

Briefly explain your answer to the previous question (whether Pluto should be a planet).
"I think that it should be considered a planet because it orbits the sun. Just because it doesn't fit into the terrestrial or jovian category doesn't mean it should be disregarded. "Pluto doesn't posses characteristics similar of those to jovian or terrestrial planets. As explained in the book it is more of a icy cold little object and there are tons it therefore I don't consider it a planet."

"I believe that Pluto is a planet because it orbits the sun and that qualifies it as a planet."

"It has certain aspects that could and couldn't make it a planet so I decided to stay neutral."

"It already was considered a planet. It still revolves around the sun no matter what we call it."

"Until more recently, I grew up learning about Pluto as a planet so do not really understand the sudden change."

It was a planet for 76 years, so I think it should have stayed that way."

"Pluto does not dominate its orbit, which makes it a dwarf planet."

"Pluto is much more similar to the family of icy worlds found recently than it is to the other eight planets in the solar system."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"I wasn't able to make it last class to the quiz. You drop three quizzes, correct?" (Yes.)

"Could we possibly go over last week's quiz?" (You need to do that yourself, but feel free to ask me questions when I'm circulating through the class during group work, just after class, in office hours, or make an appointment, or e-mail me. In any case, we'll have a practice quiz tonight to review the earlier quizzes, as well as the new material covered on the quiz next week.)

"Can we go over the geologic activity of Venus and Mars in relation to Earth?" (Yes, looking over some of your responses on this online reading assignment, we'll need to.)

Online reading assignment: uniform circular motion

Physics 205A, fall semester 2015
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 uniform circular motion.


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.
"A centrifugal force appears to push outwards on us when in fact the net force acts inwards, to keep it moving in a circular motion."

"The requirement for uniform circular motion is that the net force must be exactly equal to mv2/r, and be directed in towards the center."

"Uniform circular motion is related to Newton's second law."

"An object in uniform circular motion is constantly accelerating towards the center of the circle. A 'centripetal' force is not actually a force; it just describes the net force acting towards the center of a circle in uniform circular 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.
"Everything. I have no idea how to apply any of these concepts and barely understand the basics of them."

"I have a preliminary understanding of circular motion, at face value, but I think it would be very helpful to go over examples in class."

"I think I understand this part pretty well."

For the "drifting" car (skidding around a circular track at constant speed), Newton's __________ law applies to its motion, and the forces acting on it add up to a net force that:
first; is zero.   ******** [8]
second; points to the left.   *********************** [23]
second; points to the right.     *********************** [23]
(Unsure/lost/guessing/help!)   **** [4]


At the moment when the woman is at the bottom of her swinging trajectory (when the rope is vertical), Newton's __________ law applies to her motion, and the forces acting on her add up to a net force that:
first; is zero.   **************** [16]
second; points upwards.     *************************** [27]
second; points downwards.   ********** [10]
(Unsure/lost/guessing/help!)   ***** [5]


At the moment when the motor scooter is on the left side of the screen (traveling out at you), Newton's __________ law applies to its motion, and the forces acting on it add up to a net force that:
first; is zero.   ********* [9]
second; points to the left.   ***************** [17]
second; points to the right.   ************************ [24]
(Unsure/lost/guessing/help!)   ******** [8]


At the moment when the car is at the very top of the loop-the-loop, Newton's __________ law applies to its motion, and the forces acting on it add up to a net force that:
first; is zero.   ***************************** [29]
second; points upwards.   ********* [9]
second; points downwards.     ************************* [25]
(Unsure/lost/guessing/help!)   **** [4]


At the moment when a person is at the right edge of the screen (traveling out at you), Newton's __________ law applies to his/her motion, and the forces acting on him/her add up to a net force that:
first; is zero.   *** [3]
second; points to the left.   ************************** [26]
second; points to the right.   ***************** [17]
(Unsure/lost/guessing/help!)   ************ [12]


At the moment when the car is at the very top of its mid-air trajectory, Newton's __________ law applies to its motion, and the forces acting on it add up to a net force that:
first; is zero.   ************* [13]
second; points upwards.   ********** [10]
second; points downwards.   *************************** [27]
(Unsure/lost/guessing/help!)   ******** [8]


At the moment when the skateboarder is at the very top of his mid-air trajectory, Newton's __________ law applies to his motion, and the forces acting on him add up to a net force that:
first; is zero.   ***************** [17]
second; points upwards.   ***** [5]
second; points downwards.   ****************************** [30]
(Unsure/lost/guessing/help!)   ****** [6]


Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"I'm confused as to how circular motion applies to everyday life. I'm not fully understanding how the pictures show the centrifugal forces." (A "centrifugal" force is not one of the actual mechanical forces (w, N, T, fs, or fk). #smh)

"I'm not sure which way the net forces are acting in the examples above, so I was taking educated guesses." (#facepalm)

"Are the the net forces always towards the center of the circle (downward if at the top, upward if at the bottom, right if it's going left, left if it's going right)?" (Yes--yes, yes, yes, and yes.)

"Do we get marked down for checking 'unsure/lost/guessing/help!' or 'honestly didn't get to it yet' in our online homework?" (You will still receive full credit. Unless you leave the comment boxes blank, so put something substantive in there--even if you got nothing, at least tell me what's going on in your life that is interfering with studying physics this week.)

"7-Up or Sierra Mist?" (Meh. I do miss dnL, which was the "uʍop ǝpᴉsdn" edition of 7-Up.)

20150922

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

Astronomy 210, fall semester 2015
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.
"Venus may have been similar to Earth, just with a different atmosphere, and being slightly closer to the sun."

"All of the histories of the planets. What astronomers think the planets were like billions of years ago. And to think that some planets might have had life forms, billions of years ago."

"That Hawaii has shield volcanoes like the ones on Mars."

"How sunlight affects the color of the clouds in the atmosphere of Jupiter and Saturn."

"Learning about planets' atmospheres because it helps me understand why we can have life on Earth and not on other terrestrial planets."

"That Venus and Mars were both considered runaway planets."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"Why Pluto was deemed not a planet in 2006. I get the reasoning, but it just seems stupid."

"Atmosphere stuff: outgassing, retention, carbon cycles. All of it."

"There is no plate tectonics on Venus, how is that true?"

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 [33%]
Geologic activity, today: less than Earth [59%]
Volcanic outgassing, up until now: about the same as Earth [41%]
Heat from the sun: more than Earth [81%]
Amount of atmosphere, today: more than Earth [63%]

Identify the relative amounts of these characteristics for Mars, compared to Earth. (Only correct responses shown.)
Interior core heat, today: less than Earth [85%]
Geologic activity, today: less than Earth [56%]
Volcanic outgassing, up until now: less than Earth [70%]
Heat from the sun: less than Earth [74%]
Amount of atmosphere, today: less than Earth [70%]

Which jovian planet has the coolest interior temperatures?
Jupiter (most massive).   ** [2]
Saturn (most prominent rings).   ** [2]
Uranus (least active weather patterns).   ****** [6]
Neptune (farthest from the sun).   *********** [11]
(Unsure/guessing/lost/help!)   ****** [6]

I believe Pluto should be a planet.
Strongly disagree.   ** [2]
Disagree.   ** [2]
Neutral.   ************* [13]
Agree.   ******* [7]
Strongly Agree.   *** [3]

Briefly explain your answer to the previous question (whether Pluto should be a planet).
"Based on the current definition Pluto is not a planet. However, just because we want to change the definition does not mean that Pluto should suffer."

"Since Pluto has moons, then to me it is a planet."

"I don't know enough about Pluto to make a clear decision."

"Pluto is cute and I think it is sad to declare it a planet then take it away."

"Live and let live. I have always known Pluto as a planet."

"I don't really care much. I kind of feel like, why change it now? But now that I've read a bit more, Pluto doesn't meet some of the criteria to be considered a planet so I understand them making the change."

"I grew up with Pluto being labeled a planet. But now it's not and I'm not bothered by it."

" If we let Pluto be a planet, we'll probably have to let other dwarf planets (Eris, Ceres, etc.) be planets as well."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"I need more lecture time in class." (Well, sure, as long as you keep telling me specifically what you need more clarification on.)

"I would like it if we had more time to review for the quizzes. I studied a good amount of time and still did bad on the last quiz. Maybe I am studying the wrong things, or just not understanding. It would be helpful if we went over it more in class." (Let's have a discussion later about what you're doing (or not doing). Meanwhile, we'll have a practice quiz for review this week to prepare for the next upcoming quiz.)

"What are your thoughts on Pluto? Do you believe it should be considered a planet?" (Did we not already talk about this on the first day of semester?)

20150921

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

Physics 205A, fall semester 2015
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.
"Static friction acts to prevent objects from starting to slide. Kinetic friction acts to try to make sliding objects stop sliding."

"Kinetic friction occurs when two objects are moving relative to each other while static friction is when the two objects are not moving. Kinetic friction is usually less than the static friction."

"Different materials have different coefficients of friction."

"Frictional forces are parallel to surfaces."

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.
"Still having difficulty distinguishing the differences of Newton's first law and the third law."

"The differences between static friction and kinetic friction. Not sure how they are different."

"I don't really understand how to identify the magnitudes of static and kinetic frictional forces, and how to tell the difference(s) between them."

"I got this."

"I would like to go over more problems and more thorough explanation of the concepts during lecture."

What is the meaning of the "normal" in the "normal force?"
"Perpendicular."

"The perpendicular component of the force that acts on the object from a surface."

"'Normal' force is the average force exerted."

"It's the force 'normally' existing because of gravity?"

"The force that is applied due to gravity."

"I'm not sure."

The SI (Système International) units of the static friction coefficient µs and the kinetic friction coefficient µk are:
"These are measured in newtons (N)."

"Micros."

"These coefficients are unitless."

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 horizontal forces applied to it, so it remains stuck to the floor:
fs = 0. [78%]

A horizontal force applied to it, but still remains stuck to the floor:
fs = some value between 0 and µs·N. [75%]

A horizontal force applied to it, at the threshold of nearly becoming unstuck:
fs = µs·N. [73%]

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 horizontal forces on it, so it slows down:
fk = µk·N. [20%]

A horizontal force applied in the forward direction, but not enough to keep the box going so it still gradually slows down:
fk = µk·N. [14%]

A horizontal force applied in the forward direction, just enough to keep the box going at a constant speed:
fk = µk·N. [58%]

A horizontal force applied in the forward direction, enough to gradually increase the speed of the box:
fk = µk·N. [47%]

A horizontal force applied in the backwards direction, such that the box slows down:
fk = µk·N. [29%]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"I don't understand static friction vs. kinetic friction--the book doesn't do a great job at explaining each and whether their magnitude is zero, or not zero, etc."

"I like your online presentation previews much more than only reading from the text."

"We're going to need to talk about this." (Yes. A lot.)

"Like that you lectured last time--I actually learned a little. Can you please keep doing it that way? But instead teach us everything that will be in the midterms :D" (Hopefully maybe such that you can answer essay questions on friction on the midterm. #dreams #squadgoals)

"I LOVE PHYSICS." (Yes, but does physics love you back? #noitdont)

20150919

Physics quiz question: speed(?) of pushed box

Physics 205A Quiz 3, fall semester 2012
Cuesta College, San Luis Obispo, CA

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

A 5.0 kg box on a table is initially stationary, and then pushed with an applied force that is slowly increased from zero to 8.0 N. The coefficient of static friction between the box and table is 0.18. The coefficient of kinetic friction between the box and table is 0.15. After the applied force has reached and is maintained at a constant magnitude of 8.0 N, the speed of the box is:
(A) zero (stationary).
(B) slowing down.
(C) a constant non-zero value.
(D) speeding up.
(E) (Not enough information is given.)

Correct answer (highlight to unhide): (A)

The box has two vertical forces acting on it:
Weight force of Earth on box (downwards, magnitude w = m·g = 49 N).
Normal force of floor on box (upwards, magnitude N = 49 N).
Because the box is stationary in the vertical direction, these two forces are equal in magnitude and opposite in direction, due to Newton's first law.

The box has two horizontal forces acting on it:
Friction (static or kinetic) force of floor on box (to the left).
External applied force on box (to the right).
The (constant) magnitude of the kinetic friction force is fk = μk·N = (0.15)(49 N) = 7.4 N. The magnitude of the static friction force can vary anywhere from 0 to a maximum value of fs,max = μs·N = (0.18)(49 N) = 8.8 N. Because the applied force (increased from 0 to a maximum of 8.0 N) is less than the maximum static friction force magnitude of fs,max = 8.8 N, the actual magnitude of the static friction force would also be fs = 8.0 N to oppose the applied force, and the box would still remain stuck to the table.

Sections 70854, 70855
Exam code: quiz03sQr7
(No results available)

Astronomy quiz question: next full moon after total lunar eclipse

Astronomy 210 Quiz 2, fall semester 2015
Cuesta College, San Luis Obispo, CA

Observers in San Luis Obispo, CA will see a total lunar eclipse in the evening of September 27, 2015.[*][**] There will not be a total lunar eclipse in the following month because:
(A) the moon always keeps the same side facing Earth.
(B) the moon's orbit around Earth is tilted.
(C) the moon's orbit is not a perfect circle.
(D) Earth's axis precesses over a 23,000 year cycle.

[*] timeanddate.com/eclipse/lunar/2015-september-28.
[**] eclipse.gsfc.nasa.gov/LEplot/LEplot2001/LE2015Sep28T.pdf.

Correct answer (highlight to unhide): (B)

When the moon is full and the moon's orbit is seen edge-on from the sun's perspective, there will be a total eclipse as the moon passes completely behind Earth, in Earth's umbral shadow. However, the moon's orbit will typically change its tilt such the subsequent full moon will no longer pass directly behind Earth, being either too high or low to pass into Earth's umbral shadow, making it just a regular full moon instead of a total lunar eclipse.


Response (A) explains why the near side of the moon appears to be constant; response (C) explains why some solar eclipses are annular rather than total; and response (D) is the reason why Polaris will not always be the pole star.

Section 70158
Exam code: quiz02s5Sz
(A) : 3 students
(B) : 25 students
(C) : 13 students
(D) : 1 student

Success level: 63% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.83

Section 70160
Exam code: quiz02Nnz2
(A) : 0 students
(B) : 16 students
(C) : 13 students
(D) : 0 students

Success level: 57% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.75

Astronomy quiz question: evening star Jupiter?

Astronomy 210 Quiz 2, fall semester 2015
Cuesta College, San Luis Obispo, CA

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


At sunset (6 PM), Jupiter will be:
(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): (D)

If a dashed line is drawn from Earth to the sun, the observer at sunset (6 PM) is located perpendicular to that line.


Everything below that line would be below the horizon, such that Jupiter would not be visible at sunset, as it would be below the east horizon. (However, Mars would be visible at sunset, as it would be low above the west horizon, just above the setting sun.)

Section 70158
Exam code: quiz02s5Sz
(A) : 10 students
(B) : 7 students
(C) : 7 students
(D) : 18 students

Success level: 45% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.47

Astronomy quiz question: evening star Mercury?

Astronomy 210 Quiz 2, fall semester 2015
Cuesta College, San Luis Obispo, CA

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


At sunset (6 PM), Mercury will be:
(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 dashed line is drawn from Earth to the sun, the observer at sunset (6 PM) is located perpendicular to that line.


Everything below that line would be below the horizon, such that Mercury is visible at sunset, low in the west horizon, just over the setting sun. (However, Venus would not be visible at sunset, as it would be below the west horizon.)

Section 70160
Exam code: quiz02Nnz2
(A) : 7 students
(B) : 2 students
(C) : 12 students
(D) : 8 students

Success level: 45% (including partial credit for multiple-choice)
Discrimination index (Aubrecht & Aubrecht, 1983): 0.50

20150918

Astronomy current events question: IceCube Neutrino Observatory

Astronomy 210L, fall semester 2015
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!)
Terry Devitt, "New Data from Antarctic Detector Firms Up Cosmic Neutrino Sighting" (August 20, 2015)
news.wisc.edu/23954
To confirm that cosmic neutrinos come from outside the Milky Way, the IceCube Neutrino Observatory was buried deep in the Antarctic ice to:
(A) isolate it from earthquakes.
(B) filter out background particles.
(C) detect gravity waves.
(D) reach absolute zero temperatures.
(E) block GPS interference.

Correct answer: (B)

Student responses
Sections 70178, 70186
(A) : 0 students
(B) : 20 students
(C) : 13 students
(D) : 4 students
(E) : 0 students

Astronomy current events question: mass of dwarf galaxy RGG 118's central black hole

Astronomy 210L, fall semester 2015
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!)
Nicole Casal Moore, "Astronomers Find 'Teeny Supermassive Black Hole'" (August 11, 2015)
ns.umich.edu/new/releases/23057-astronomers-find-teeny-supermassive-black-hole
Researchers determined the mass of dwarf galaxy RGG 118's central black hole by measuring the:
(A) disappearance of nearby stars.
(B) distortion of background stars.
(C) pull on other galaxies.
(D) motion of gas around it.
(E) ripples in spacetime.

Correct answer: (D)

Student responses
Sections 70178, 70186
(A) : 7 students
(B) : 9 students
(C) : 6 students
(D) : 14 students
(E) : 1 student

Astronomy current events question: New Horizon's potential visit to 2014 MU69

Astronomy 210L, fall semester 2015
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!)
Tricia Talbert, "NASA’s New Horizons Team Selects Potential Kuiper Belt Flyby Target" (August 28, 2015)
nasa.gov/feature/nasa-s-new-horizons-team-selects-potential-kuiper-belt-flyby-target/
After its Pluto flyby, NASA's New Horizons spacecraft may visit 2014 MU69, a small Kuiper Belt object expected to have the same composition as:
(A) rogue asteroids.
(B) the original outer solar system.
(C) solar wind remnants.
(D) dark matter.
(E) Saturn's rings.

Correct answer: (B)

Student responses
Sections 70178, 70186
(A) : 12 students
(B) : 17 students
(C) : 0 students
(D) : 0 students
(E) : 8 students

Physics quiz question: speeding-up Jeep Renegade

Physics 205A Quiz 2, fall semester 2015
Cuesta College, San Luis Obispo, CA

"2015 Jeep® Renegade Limited"
Fiat Chrysler Automobiles: Corporate
flic.kr/p/q1FppQ

According to Car and Driver[*] magazine a 2015 Jeep Renegade Limited 4×4 is able to accelerate at 2.7 m/s2 from an initial speed of 2.2 m/s over 9.2 seconds. Assume that the road is horizontal, and that the acceleration of the Jeep Renegade is constant and always points in the same direction as its velocity. The final speed of the Jeep Renegade is:
(A) 11 m/s.
(B) 23 m/s.
(C) 25 m/s.
(D) 27 m/s.

[*] Daniel Pund, "2015 Jeep Renegade Limited 4×4" (February 2015), caranddriver.com/reviews/2015-jeep-renegade-limited-4x4-test-review.

Correct answer (highlight to unhide): (D)

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

(x0 = 0 m),
(t0 = 0 s),
t = 9.2 s,
v0x = +2.2 m/s,
ax = +2.7 m/s2.

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 vx to be solved for appearing in the first equation, with all other quantities given (or assumed to be known), then:

vx = v0x + ax·t,

vx = (+2.2 m/s) + (+2.7 m/s2)·(9.2 s),

vx = +27.04 m/s,

of which the magnitude is the final speed, to two significant figures, is 27 m/s.

(Response (A) is ax·t/v0x; response (B) is -v0x + ax·t; response (D) is ax·t.)

Sections 70854, 70855, 73320
Exam code: quiz02J3eP
(A) : 2 students
(B) : 5 students
(C) : 7 students
(D) : 58 students

Success level: 80%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.81

Physics quiz question: comparing average accelerations from velocity graph

Physics 205A Quiz 2, fall semester 2015
Cuesta College, San Luis Obispo, CA

The vx(t) graph of two cars traveling in a straight line are shown at right. The object starts at x = 0 at t = 0.

_________ experiences the greater magnitude average acceleration from t = 0 to t = 8 s.
(A) Car 1.
(B) Car 2.
(C) (There is a tie.)
(D) (Not enough information is given.)

Correct answer (highlight to unhide): (A)

For car 1, since the slope of its vx(t) graph is unchanged from t = 0 to t = 8 s, then the average acceleration (given by the chord slope) for that time interval will be identical to the tangent slope for any instant of time in that interval, given by:

car 1: aav,x = chord slope = (+6 m/s)/(8 s) +0.75 m/s2.

For car 2, since the slope of its vx(t) graph changes at t = 4 s, then the average acceleration must be explicitly given by the chord slope that has endpoints at t = 0 and t = 8 s:

car 2: aav,x = chord slope = ∆vx/∆t = (3 m/s)/(+8 s) = +0.375 m/s2.

Sections 70854, 70855, 73320
Exam code: quiz02J3eP
(A) : 42 students
(B) : 13 students
(C) : 16 students
(D) : 0 students

Success level: 57%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.69

Physics quiz question: free fall with Despicable Me Minion

Physics 205A Quiz 2, fall semester 2015
Cuesta College, San Luis Obispo, CA

In July 2015 a girl fell out of a third-story apartment window, but landed with only a broken arm, her fall reportedly cushioned with a stuffed Minion doll from the movie Despicable Me.[*] Assume that girl fell 9.0 m downwards, with no initial vertical velocity. Neglect air resistance. Choose up to be the +y direction.

"Toy Department"
Miguel Tejada-Flores
flic.kr/p/re7Xwr

The elapsed time for the girl to fall and reach the ground was:
(A) 1.1 s.
(B) 1.4 s.
(C) 1.8 s.
(D) 2.2 s.

[*] Associated Press, "Police: Minion Toy Broke Girl's Fall from Window," July 20, 2015, wwlp.com/2015/07/20/police-minion-toy-broke-girls-fall-from-window/.

Correct answer (highlight to unhide): (B)

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

(t0 = 0 s),
(y0 = 0 m),
y = –9.0 m (below the starting point),
v0y = 0 m/s (no initial velocity),
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 t to be solved for appearing in the third equation, with all other quantities given (or assumed to be known), then:

y = v0y·t + (1/2)·ay·(t)2,

(–9.0 m) = (0 m/s)·t + (1/2)·(–9.80 m/s2t2,

1.355261854 s = t,

or to two significant figures, the elapsed time for the girl to fall is 1.4 s.

(Response (A) is ay/y; response (C) is 2·y/ay; response (D) is sqrt(ay/2).)

Sections 70854, 70855, 73320
Exam code: quiz02J3eP
(A) : 14 students
(B) : 50 students
(C) : 5 students
(D) : 3 students

Success level: 70%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.69

Physics quiz question: decimal places resulting from addition/subtraction operation

Physics 205A Quiz 1, fall semester 2015
Cuesta College, San Luis Obispo, CA

Evaluate the following calculation, using an appropriate number of significant figures and/or decimal places.

      93.450 s – 88 s + 0.7 s = ?

(A) 6 s.
(B) 6.2 s.
(C) 6.15 s.
(D) 6.150 s.

Correct answer (highlight to unhide): (A)

For the addition and subtraction operations, the term with the least number of decimal places (shown in gray) determines the number of significant decimal places in the result.

93.450 s – 88 s + 0.7 s.

Since 93.450 s has two decimal places, 88 s has no decimal places, and 0.7 has only one decimal place, then the result of adding or subtracting these numbers will only have no significant decimal places.

Thus:

93.450 s – 88 s + 0.7 s = 6.15 s,

should be truncated with no decimal places to 6 s.

Sections 70854, 70855, 73320
Exam code: quiz01rdBL
(A) : 46 students
(B) : 21 students
(C) : 5 students
(D) : 8 students

Success level: 58%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.71

Physics quiz question: daily Red Bull® caffeine consumption rate

Physics 205A Quiz 1, fall semester 2015
Cuesta College, San Luis Obispo, CA

A single can of Red Bull® beverage containing 80 mg of caffeine[*] is consumed once a day. Assuming that no other caffeinated beverages are consumed, the average daily intake of caffeine in grams per second is:
(A) 1.2×10–8 g/s.
(B) 2.8×10–7 g/s.
(C) 9.3×10–7 g/s.
(D) 2.2×10–5 g/s.

[*] energydrink-us.redbull.com/caffeine-red-bull.

Correct answer (highlight to unhide): (C)

The intake in grams per second can be determined from converting the units from the given rate of 80 mg per day by setting up conversion factors such that unwanted units cancel (mg, day) while desired units remain (g, s):

(80 mg/day)·(1 g/1000 mg)·(1 day/24 h)·(1 h/60 min)·(1 min/ 60 s),

= 9.259259×10–7 g/s,

which to two significant figures, is 9.3×10–7 g/s.

(Response (A) is the result of ingesting 1 mg of caffeine a day; response (C) is the result of ingesting 1 mg of caffeine an hour, while response (D) is the result of drinking one Red Bull® beverage every hour; response (D) is the result of ingesting 1 g of caffeine every hour.)

Sections 70854, 70855, 73320
Exam code: quiz01rdBL
(A) : 4 students
(B) : 3 students
(C) : 72 students
(D) : 1 student

Success level: 90%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.21

Physics quiz question: cubic centimeter equivalent of a gallon

Physics 205A Quiz 1, fall semester 2015
Cuesta College, San Luis Obispo, CA

According to the National Institute of Standards and Technology[*], the U.S. liquid gallon is defined to be exactly 231 in3, and the inch is defined to be exactly 2.54 cm. A U.S. liquid gallon is equivalent to:
(A) 7.09396709×10–2 cm3.
(B) 1.40964848859×101 cm3.
(C) 5.8674×102 cm3.
(D) 3.785411784×103 cm3.

[*] nist.gov/pml/wmd/pubs/upload/HB130-11-final.pdf.

Correct answer (highlight to unhide): (D)

Then setting up conversion factors such that unwanted units cancel (gallon, inches) while desired units remain (centimeters):

1 gallon = 231 in3·(2.54 cm/1 in)·(2.54 cm/1 in)·(2.54 cm/1 in),

such that:

1 gallon = 3.785411784×103 cm3.

Since the 1 in = 2.54 cm conversion factor is exact, then presumably this equivalent amount of cm3 for 1 gallon retains all figures as significant.

Sections 70854, 70855, 73320
Exam code: quiz01rdBL
(A) : 0 students
(B) : 0 students
(C) : 13 students
(D) : 66 students

Success level: 83%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.46

Physics quiz question: first radiation constant

Physics 205A Quiz 1, fall semester 2015
Cuesta College, San Luis Obispo, CA

The first radiation constant c1 is given by the expression[*]:

c1 = 2πh·c2.

The Planck constant h is measured in units of kg·m2·s–1, and the speed of light c is measured in units of m·s–1. The units for the first radiation constant c1 are:
(A) kg2·m5·s–3.
(B) kg1/2·m2·s–3/2.
(C) kg·m3·s–2.
(D) kg·m4·s–3.

[*] goldbook.iupac.org/R05051.html.

Correct answer (highlight to unhide): (D)

Replacing the quantities in the equation for the first radiation constant with their kg, m and s units (while also ignoring the 2π term, as it is unitless); the units of c1 are:

c1 = kg·m2·s–1·(m·s–1)2,

c1 = kg·m2·s–1·m2·s–2,

c1 = kg·m4·s–3.

Sections 70854, 70855, 73320
Exam code: quiz01rdBL
(A) : 2 students
(B) : 1 student
(C) : 15 students
(D) : 62 students

Success level: 78%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.41

Physics quiz question: maximum shear stress

Physics 205A Quiz 1, fall semester 2015
Cuesta College, San Luis Obispo, CA

The maximum shear stress τ (measured in units of kg·m–1·s–2) in a round solid bar subject to impact is given by the expression[*]:

τ = 2√(E·S/V).

The change in energy E is measured in units of kg·m2·s–2, and the volume V of the rod is measured in units of m3. The units for the shear modulus S are:
(A) kg3·m–3·s–6.
(B) kg–3·m–3·s–6.
(C) kg·m–1·s–2.
(D) (No units, as it is a dimensionless quantity.)

[*] wki.pe/Shear_stress.

Correct answer (highlight to unhide): (C)

The shear modulus S can be expressed as:

S = τ2·V/E,

and replacing the quantities in the equation with their kg, m and s units, the units of S are:

S = (kg·m–1·s–2)2·m3/(kg·m2·s–2),

S = kg2·m–2·s–4·m3/(kg·m2·s–2),

S = kg·m–1·s–2.

Sections 70854, 70855, 73320
Exam code: quiz01rdBL
(A) : 13 students
(B) : 4 students
(C) : 55 students
(D) : 8 students

Success level: 69%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.45

20150917

Astronomy quiz archive: eclipses/history of astronomy

Astronomy 210 Quiz 2, fall semester 2015
Cuesta College, San Luis Obispo, CA

Section 70158, version 1
Exam code: quiz02s5Sz


Section 70158
0- 8.0 :  
8.5-16.0 :   ********** [low = 8.5]
16.5-24.0 :   *********** [mean = 23.1 +/- 8.2]
24.5-32.0 :   **************
32.5-40.0 :   ******* [high = 40.0]


Section 70160, version 1
Exam code: quiz02Nnz2


Section 70160
0- 8.0 :  
8.5-16.0 :   ******* [low = 9.0]
16.5-24.0 :   ********* [mean = 23.5 +/- 7.7]
24.5-32.0 :   ********
32.5-40.0 :   ***** [high = 36.0]

20150916

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

Astronomy 210, fall semester 2015
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.
"That telescopes viewing infrared radiation must be cooled. I never suspected that the heat of the telescopes themselves, in basic terms, produced their own light pollution that made the image hard to see."

"The 'turkey/cornish hen effect'--it really was a great image and explanation of core temperatures of different-size planets."

"Adaptive optics was interesting me, learning how telescopes can be altered to in a sense, to get rid of the 'atmosphere' to see space more clearly."

"The large-impact hypothesis that the moon formed from debris of a collision between Earth and some other large object in space."

"That tturbulence in the atmosphere that makes stars look like they're twinkling in the night sky."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"During outgassing how is water released from rock?"

"How Earth's deep layer of dense rock can slowly flow like a liquid."

"How active optics gets rid of atmospheric turbulence."

"The large impact hypothesis."

"The greenhouse effect, and how the ocean can absorb large amounts of carbon dioxide from the atmosphere."

Stars to appear to "twinkle" in the night sky because of:
"Turbulence in the Earth's atmosphere."

"Because we view them through moving air."

"I don't know."

A large modern optical telescope in outer space would have images with better __________ than a comparable ground-based telescope.
brightness. ****** [6]
resolution. ************ [12]
magnification. * [1]
(None of the above choices.) * [1]
(Two of the above choices.) *********** [11]
(All of the above choices.) ******* [7]
(Unsure/guessing/lost/help!) * [1]

Identify how carbon dioxide enters and how it is taken out of Earth's atmosphere.
(Only correct responses shown.)
Enters atmosphere from: volcanoes [54%]
Taken out of atmosphere by: oceans [59%]

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) [38%]
Flat lava plains: middle [%37]
Craters on top of flat lava plains: youngest (formed most recently) [51%]

Identify the oldest (longest ago) to the youngest (most recent) features on Mercury.
(Only correct responses shown.)
Large crater basins: oldest (formed longest ago) [55%]
Lava-filled lowlands: middle [49%]
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.
"Can you clarify how active optics rid of atmospheric turbulence?" (Yes.)

"The presentation on Earth and the greenhouse effect contained five uses of the word, 'subsequent.'"

"This class is sick as frick." (I don't know how to respond to that.)

"How do craters get filled with lava?" (If there is a large enough volcanic eruption, lava fills in everything.)

"How much did the telescope at the Bowen Observatory cost?" (The Meade LX200-ACF 14" f/10 telescope was purchased from a Cuesta College Foundation grant for approximately $6,000-7,000 about ten years ago.)