20160930

Astronomy current events question: moon and large earthquake correlation?

Astronomy 210L, fall semester 2016
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!)
Nathaniel Scharping, "Can the Moon Make an Earthquake Worse?" (September 12, 2016)
blogs.discovermagazine.com/d-brief/2016/09/12/is-the-moon-making-earthquakes-worse/
Researchers found that gravitational forces from the moon and large earthquakes may have:
(A) a statistical correlation.
(B) a cause-and-effect relationship.
(C) a common source of energy.
(D) remnants of the moon's large impact origin.
(E) started Earth's tectonic plate motion.

Correct answer: (A)

Student responses
Sections 70178, 70186
(A) : 12 students
(B) : 8 students
(C) : 3 students
(D) : 0 students
(E) : 5 students

Astronomy current events question: recent ages of Mars' lakes

Astronomy 210L, fall semester 2016
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!)
Guy Webster, Dwayne Brown, and Laurie Castillo, "Some Ancient Mars Lakes Came Long After Others" (September 15, 2016)
jpl.nasa.gov/news/news.php?feature=6619
Some ancient lakes on Mars may have formed relatively recently, as determined by comparing inlet valley features with the ages of overlapping:
(A) glaciers.
(B) lava flows.
(C) sedimentary layers.
(D) rift zones.
(E) impact craters.

Correct answer: (E)

Student responses
Sections 70178, 70186
(A) : 2 students
(B) : 2 students
(C) : 13 students
(D) : 2 students
(E) : 8 students

Astronomy current events question: red spots on Charon

Astronomy 210L, fall semester 2016
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!)
Nola Taylor Redd, "Weird Red Spot on Pluto's Moon Charon Caused by Traveling Atmosphere" (September 14, 2016)
space.com/34066-pluto-moon-charon-red-spot-source.html
Computer models suggest that the red spot on the north pole of Pluto's moon, Charon, may be organic molecules from Pluto's:
(A) cryovolcanoes.
(B) atmosphere.
(C) ancient lifeforms.
(D) rings.
(E) magnetic fields.

Correct answer: (B)

Student responses
Sections 70178, 70186
(A) : 4 students
(B) : 23 students
(C) : 0 students
(D) : 0 students
(E) : 0 students

20160929

Astronomy quiz archive: telescopes

Astronomy 210 Quiz 3, fall semester 2016
Cuesta College, San Luis Obispo, CA

Section 70158, version 1
Exam code: quiz03S7ew


Section 70158
0- 8.0 :  
8.5-16.0 :   ******* [low = 9.0]
16.5-24.0 :   ************* [mean = 23.2 +/- 7.7]
24.5-32.0 :   **************
32.5-40.0 :   ***** [high = 40.0]


Section 70160
Exam code: quiz03n0oN


Section 70160
0- 8.0 :   * [low = 7.0]
8.5-16.0 :   **
16.5-24.0 :   *********** [mean = 23.3 +/- 7.6]
24.5-32.0 :   ******
32.5-40.0 :   ***** [high = 36.5]

20160928

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

Astronomy 210, fall semester 2016
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.
"An atom has electrons. The electrons orbits the nucleus. The atom has energy levels in which the electrons can jump from one energy level to another."

"I liked the analogy of lava lamps and miso soup to describe the surface of the sun. It made it easier to understand."

"I found it interesting that different atoms emit different photons of color. After reading this it made sense but it was something that I never really thought of."

"How the sunspots aren't actually black in color, that the bright surface surrounding the sun spot just makes it appear black when really it's not."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"I understood the electron rule and the proton rule but I don't understand why they make colors in the neon lights. The book defines atom, isotope, electron, proton etc., but I still do not understand what they do and how they are arranged."

"Any and all talk of atoms, nuetrons, protons, etc. I did not understand quantum jumps and orbiting of electrons, etc."

"The photons creating different colors in tube lights is a little confusing, because my knowledge of chemistry is limited but it is interesting nonetheless."

"Corona, I don't see the 'wings.'"

"Sunspots. There's a lot more to them than I originally thought. More complex."

"ELECTRONS!"

An electron in an atom must emit a photon when it jumps from a __________ energy orbital to a __________ energy orbital.
lower; higher.  ********** [10]
higher; lower.  ********************* [21]
(Both of the above choices.)  [0]
(Unsure/guessing/lost/help!)  ** [2]

An electron in an atom must absorb a photon when it jumps from a __________ energy orbital to a __________ energy orbital.
lower; higher.  ****************** [18]
higher; lower.  *********** [11]
(Both of the above choices.)  ** [2]
(Unsure/guessing/lost/help!)  ** [2]

The exterior of the sun, from inner to outermost layers, are the:
(Only correct responses shown.)
inner: photosphere [61%]
middle: chromosphere [64%]
outer: corona [67%]

State your preference regarding miso soup.
Strongly dislike.  * [1]
Dislike.  *** [3]
Neutral.  **** [4]
Like  ********** [10]
Strongly like.  ************ [12]
(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.
"How would you advise me to study the content in this class to earn an 'A?'" (Students from last semester have some advice for you on what was helpful (or not helpful) for studying for the first midterm.)

"Miso soup is good but without some chili paste and soy sauce it isn't nearly as good."

"All of the presentations make me hungry." (Me, too.)

Online reading assignment: energy conservation

Physics 205A, fall semester 2016
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.
"An object in motion has translational kinetic energy. The value of the gravitational potential energy will get larger or smaller depending on the height. Kinetic energy of motion can be converted into potential energy of position."

"Translational kinetic energy is in everything that has motion. Gravitational potential energy is a function of height above the surface. Elastic potential energy is energy that is a result of say, a spring or a rubber band."

"The energy of conservative forces can be retrieved without loss. Also non-conservative forces involve transfer or loss of energy when work is done."

"Gravitational potential energy depends on from where an object is dropped. The higher up an object is, the greater gravitational potential energy it has."

"As long as I know the variables in equation it should be easy."

"I think that I have really grasped the idea of conservative forces and how they first store energy from an object only to give it back. This causes gravitational and elastic forces to work in essentially the same way, and therefore have similar equations."

"Potential gravitatinal energy changes based on height and the elastic potential energy changes by the distance the spring/band stretches/contracts. I understand that these energies can be irreversibly lost to work done by friction and drag."

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.
"These sections related many equations to each other, further review will help to understand them easier."

"I am really struggling with the major concepts in these sections. Especially gravitational potential energy and kinetic energy."

"All the formulas seems very complex, all the subscripts. and the way the book is set up you only see them once. A little fuzzy on the non-conservative forces."

"I am unsure of how to figure out how gravitational potential energy works."

"Nothing yet, but I will be confused when I read it tomorrow."

"I am confused over the transfer/balance equation. Specifically, I don't understand how the kinetic, potential elastic, and potential gravitational energies have a relationship to the non-conservative work. Also why is it work zero when friction and drag are negligible?"

"I have trouble sometimes identifying where a force is. Also sometimes knowing which of Newton's laws is used."

"I am a little confused about when these conservative forces act together with non-conservative forces, because the equation is really long. I guess it's just the transfer/balance equation that confuses me."

"The practice problems at the bottom of the blog made no sense to me at all. I couldn't understand how to interrelate all of the different formulas."

"I found the different formulas a little confusing. If we could do some examples in class to clear it up that would be sweet."

"I just think applying the equations and knowing when to use them is the hardest part. Its hard to read something for the first time and see the scary equation and apply it all in my head. But that's why we go over it in class!"

"I understood the differences between conservative and non-conservative forces, but still am really confused how to get the formulas based off of them and to derive one variable out of an equation."

"There is a lot that I don't understand so the more explanation in class the better."

"I'm having trouble understanding what stored energy is. I can't really fully understand the concept of it."

"I didn't find anything confusing."

For the woman moving upwards after being catapulted, her translational kinetic energy __________ while her gravitational potential energy __________.
decreases; increases.   ******************************** [32]
increases; decreases.   ******* [7]
(Unsure/lost/guessing/help!)   ******* [7]

For the ball bearing being launched by the slingshot, its translational kinetic energy __________ while the elastic potential energy of the slingshot bands __________.
decreases; increases.   **** [4]
increases; decreases.   *********************************** [35]
(Unsure/lost/guessing/help!)   ******* [7]

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. [54%]
Gravitational potential energy: decreases. [59%]
Elastic potential energy (of the bungee cords): increases. [63%]

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.   *************** [15]
the elastic potential energy of the bungee cords.   ************ [12]
(Unsure/lost/guessing/help!)   ********* [9]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"How is translational kinetic energy and gravitational potential energy different than heat or light?" (Here we're looking at mechanical energy systems of objects on the macroscopic scale; heat and light are forms of energy on the atomic scale.)

"I do not understand how translational kinetic energy increases or decreases. If we look at it over an interval, does it count at the beginning or the end?" (There is both an initial KEtrans value and a final KEtrans value. But more interesting is the amount of ∆KEtrans change, and how it increases or decreases for a process.)

"How can the total mechanical energy of a moving object remain constant, provided that the net work done by external nonconservative forces is zero? How can  the net work done by external nonconservative forces equal zero?" ((a) If the energy forms only trade with each other, and not with the outside world; and (b) if any losses in energy by drag and friction work are offset by gains in energy put in by applied forces pushing/pulling the object forward.)

"More discussion on what makes a force conservative vs. non-conservative." (Good. Then we get to talk about sliding that cat across the floor. I like talking about cats.)

"Can we make one of those bungee swings from the top of the library?" (Who wants to be the first to test it out?)

"If we have more than one energy type in an equation, what do we do?" (I'll show you what we do in cases like that. Basically balance out (or try to balance out) the transfers between the different energy types. Or numerically plug-and-chug.)

"What would be the best way to memorize and understand these complicated-looking formulas?" (You're given all the equations for work and energy, in class today we'll take a closer look at using these equations both conceptually and in problem-solving.)

"I always understand how everything works when you go over it in class, and then I go back and look at how I solved problems in class and it looks like a different language. This is why the midterm is scary. :0" (That's normal when you're just getting started on the new stuff. We'll go back and review the old stuff next week that will be on the midterm, hopefully by then it will seem more familiar and less scary.)

20160927

Physics quiz question: horizontal velocity component of upwards-kicked soccer ball

Physics 205A Quiz 3, fall semester 2016
Cuesta College, San Luis Obispo, CA

A soccer ball is kicked from ground level with an upwards angle, with initial horizontal and vertical velocity components of 
v0x = +2.8 m/s, 
v0y = +10.6 m/s, respectively. Neglect air resistance. After the soccer ball was kicked, but just before it reaches its highest point above the ground, the magnitude of the horizontal velocity component of the ball:
(A) decreases.
(B) remains constant.
(C) increases.
(D) (Not enough information is given.)

Correct answer (highlight to unhide): (B)

For the ideal case of projectile motion were air resistance is negligible, the vertical component of the ball's velocity continuously changes (due to the downwards vertical acceleration due to gravity), while the horizontal component of the ball's velocity never changes (due to there being no horizontal acceleration).

Sections 70854, 70855, 73320
Exam code: quiz03sHO7
(A) : 9 students
(B) : 42 students
(C) : 6 students
(D) : 0 students

Success level: 74%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.43

Physics quiz question: downwards-aimed BB pellet vertical component

Physics 205A Quiz 3, fall semester 2016
Cuesta College, San Luis Obispo, CA

A BB gun shoots a pellet with a speed of 105 m/s at an angle of 40° below the horizontal, down towards the ground below. Neglect air resistance. The initial vertical velocity component of the pellet was:
(A) –67 m/s.
(B) –80 m/s.
(C) –88 m/s.
(D) –1.4×102 m/s.

Correct answer (highlight to unhide): (A)

The initial velocity vector of the BB is 40° below the horizontal, which corresponds to an angle of θ = 360° – 40° = 320°, as measured counterclockwise from the +x axis (i.e., the "unit circle angle"). Using this θ = 320° angle allows the ± signs in the initial velocity vector components to naturally result from the calculations:

v0x = v0·cosθ,
v0y = v0·sinθ.

Then the vertical component of the initial velocity vector is then:

v0y = v0·sinθ,

v0y = (105 m/s)·sin(320°) = –67.4926990171 m/s,

or to two significant figures, v0y = –67 m/s.

(Response (B) is (105 m/s)·cos(320°); response (C) is (105 m/s)·tan(320°); response (D) is (105 m/s)/cos(320°).)

Sections 70854, 70855, 73320
Exam code: quiz03sHO7
(A) : 30 students
(B) : 19 students
(C) : 7 students
(D) : 1 student

Success level: 53%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.61

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

Astronomy 210, fall semester 2016
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.
"How the sun convects heat from bottom to top just like when cooking or other common phenomena you see daily on Earth."

"That all the lights in 'neon' signs are caused by different gases."

"How a photon has to have a specific amount of energy to be able to be absorbed by an electron."

"I really enjoyed seeing the picture of the sun's chromosphere and corona, I had no idea it had those features."

"The wings on the sun during a total solar eclipse was supercool, and it's interesting that the Egyptians described it the way they did."

"How certain atoms give off different colors, due to the different energies of photons that are either emitted or absorbed."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"The photon lures and electron rules were very confusing to me. I just don't understand them."

"I do not understand the TV/magnet model to help explain what is going on in sunspots--what is the 'magnet' on the sun?"

"I was confused about the innermost electron orbit, and why it had the lowest energy there. Why, is it the closer to the nucleus, the lower its energy?"

"P-dog, I'm going to be honest that photon rule was pretty confusing to me--I don't understand why electrons want to move to outer energy levels."

"Basically everything that talks about atoms, photons, and electrons confuse me because it seems like a different language."

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.  **************** [16]
(Both of the above choices.)  * [1]
(Unsure/guessing/lost/help!)  ** [2]

An electron in an atom must absorb a photon when it jumps from a __________ energy orbital to a __________ energy orbital.
lower; higher.  **************** [16]
higher; lower.  ***** [5]
(Both of the above choices.)  * [1]
(Unsure/guessing/lost/help!)  ** [2]

The exterior of the sun, from inner to outermost layers, are the:
(Only correct responses shown.)
inner: photosphere [75%]
middle: chromosphere [83%]
outer: corona [79%]

State your preference regarding miso soup.
Strongly dislike.  * [1]
Dislike.  [0]
Neutral.  **** [4]
Like  ********* [9]
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.
"How does the convection cycle work when the sun is so extremely hot, both inside and out? It seems like the difference in temperatures wouldn't matter at those extremes." (The core of the sun, where it produces its energy from fusion, is hella hot. Outside in space, it's cold. So energy will eventually move from hot to cold, from the core to the surface of the sun to outer space.)

"Regarding grades, how do we know where we stand? Do we get an update after midterm or can we e-mail you?" (You'll get an update after every midterm; but if you can't wait, just e-mail me, see me just after class or during office hours.)

"Miso soup is delicious."

"I've never had miso soup."

That miso soup question makes miso hungry... If I couldn't get to the reading yet I can at least offer the worst joke of the year."

20160926

Physics quiz question: BB pellet average speed vs. magnitude of average velocity

Physics 205A Quiz 3, fall semester 2016
Cuesta College, San Luis Obispo, CA

A BB gun shoots a pellet with a speed of 105 m/s at an angle of 40° below the horizontal, down towards the ground below. Neglect air resistance. After being shot out of the gun, but just before it hits the ground below, the pellet's average speed was __________ the magnitude of its average velocity.
(A) less than.
(B) equal to.
(C) greater than.
(D) (Not enough information is given.)

Correct answer (highlight to unhide): (C)

The average speed of the BB is its distance traveled divided by elapsed time, while the magnitude of average velocity is given by the magnitude of displacement divided by elapsed time. For projectile motion, the distance traveled is measured along its curved trajectory, and is longer than the magnitude of the displacement, which is the length of the straight-line vector that starts from the muzzle of the BB gun, and ends where the BB hits the ground. Since the elapsed time for the BB to travel from the start to finish is the same whether along the actual distance traveled or the straight-line displacement, the average speed of the BB must be greater than the magnitude of its average velocity.

(Response (A) can never be true for any possible path taken by an object. Response (B) can only be true for an object traveling along a straight-line with no reversals in direction.)

Sections 70854, 70855, 73320
Exam code: quiz03sHO7
(A) : 8 students
(B) : 35 students
(C) : 14 students
(D) : 0 students

Success level: 25%
Discrimination index (Aubrecht & Aubrecht, 1983): –0.01

Physics quiz question: net force on accelerating sliding suitcase

Physics 205A Quiz 3, fall semester 2016
Cuesta College, San Luis Obispo, CA

A force of 85 N is applied to the right on a 25 kg suitcase that is already sliding to the right, such that it accelerates to the right with a magnitude of 1.5 m/s2. The horizontal floor is not frictionless. The magnitude of the net force on the suitcase is:
(A) 0 N.
(B) 38 N.
(C) 85 N.
(D) 2.5×102 N.

Correct answer (highlight to unhide): (B)

Since the suitcase is accelerating to the right, Newton's second law applies to its horizontal motion, such that the net force must be non-zero. There are two horizontal forces acting on the suitcase:
The applied force on suitcase (to the right, magnitude N = 85 N).
Kinetic friction force of the floor on suitcase (to the left, opposing its motion, magnitude fk = ?).
Since the suitcase is accelerating to the right, the net force points to the right, and has a magnitude of

ΣFx = m·ax,

ΣFx = (25 kg)·(9.80 N/kg) = 37.5 N,

or to two significant figures, the net force has a magnitude of 38 N.

(Response (A) only applies if the suitcase were stationary, or sliding horizontally at a constant speed, such that Newton's first law would apply; response (C) is the magnitude of the applied force (which would be the magnitude of the net force if horizontal floor were frictionless (but that would mean that the magnitude of the acceleration to the right would be different than the given value of 1.5 m/s2); response (D) is the magnitude of the weight force w = m·g.)

Sections 70854, 70855, 73320
Exam code: quiz03sHO7
(A) : 4 students
(B) : 24 students
(C) : 24 students
(D) : 5 students

Success level: 42%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.66

Physics quiz question: hanging book, suspended by crate on floor

Physics 205A Quiz 3, fall semester 2016
Cuesta College, San Luis Obispo, CA

A 2.0 kg book is suspended by an ideal pulley and rope, which is attached on the other end to a 10.0 kg crate that rests on a horizontal frictionless floor. Newton's __________ law tells you that these two forces are equal in magnitude and opposite in direction:
Weight force of Earth on the book.
Tension force of crate on the book.
(A) first.
(B) second.
(C) third.
(D) (These forces are not equal in magnitude and/or opposite in direction.)

Correct answer (highlight to unhide): (A)

The book has two vertical forces acting on it:
Weight force of Earth on book (downwards, magnitude w = m·g = 19.6 N).
Tension force of crate on book (upwards, magnitude T = ?).
Because the book is stationary in the vertical direction, from Newton's first law all of the up and down forces must sum to zero. This means that the upwards tension force must be equal in magnitude to the downwards weight force.

Sections 70854, 70855, 73320
Exam code: quiz03sHO7
(A) : 26 students
(B) : 11 students
(C) : 12 students
(D) : 8 students

Success level: 46%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.71

Physics quiz question: crate on floor, suspending a hanging book

Physics 205A Quiz 3, fall semester 2016
Cuesta College, San Luis Obispo, CA

A 2.0 kg book is suspended by an ideal pulley and rope, which is attached on the other end to a 10.0 kg crate that rests on a horizontal frictionless floor. Newton's __________ law tells you that these two forces are equal in magnitude and opposite in direction:
Weight force of Earth on the crate.
Normal force of floor on the crate.
(A) first.
(B) second.
(C) third.
(D) (These forces are not equal in magnitude and/or opposite in direction.)

Correct answer (highlight to unhide): (D)

The crate has three vertical forces acting on it:
Weight force of Earth on crate (downwards, magnitude w = m·g = 98.0 N).
Normal force of floor on crate (upwards, magnitude N).
Tension force of book on crate (upwards, magnitude T).
Because the crate is stationary in the vertical direction, from Newton's first law all of the up and down forces must sum to zero. This means that the two upwards forces (normal and tension) are together equal to the one downwards force (weight), and the upwards normal force of floor on the crate is less than the magnitude of the (opposite direction) weight force of Earth on the crate.

Sections 70854, 70855, 73320
Exam code: quiz03sHO7
(A) : 33 students
(B) : 12 students
(C) : 6 students
(D) : 6 students

Success level: 11%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.42

Physics quiz archive: vectors, projectile motion, forces

Physics 205A Quiz 3, fall semester 2016
Cuesta College, San Luis Obispo, CA
Sections 70854, 70855, 73320, version 1
Exam code: quiz03sHO7



Sections 70854, 70855, 73320 results
0- 6 :   ********** [low = 0]
7-12 :   ************************* [mean = 12.7 +/- 5.4]
13-18 :   **********
19-24 :   ******* [high = 24]
25-30 :  

Online reading assignment: work and energy

Physics 205A, fall semester 2016
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.
"Translational kinetic energy is energy of movement, and that it is affected by work. If work is done against the object then it will slow down, and if it is done on the object then it will speed up."

"Work done on an object will be force directed along the direction of the motion, and the work will have a positive sign. The work done against an object will be force exerted opposite the direction of its motion, and the work will have a negative sign."

"If the displacement of an object is zero, the work is zero no matter how much force is applied. A joule is a newton·meter. The difference between initial and final kinetic energy is the amount of work being done."

"Work is a scalar quantity, in units of joules, that requires a force and a displacement. Work-energy-theorem relates work to the change in kinetic energy. Kinetic energy is also a scalar quantity."

"Even if a force is acting on an object with mass, if there is no displacement of the object, them the amount of work being done on the object is still zero. I also understand the relationship between the force and displacement (work being done on an object) will change the kinetic energy of the object."

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.
"The actual equations for work and translational kinetic energy look a little intimidating and confusing, but I think that once we use them in examples that I will understand them better."

"I would benefit from more examples of the work-energy theorem equation."

"I don't really understand how if the displacement s is zero, then work is zero, even if a force is applied."

"I'm not 100% sure how the angle between the force and displacement vectors figure into calculating work."

"I am somewhat confused about the work-energy theorem which states that W = KEfinalKEinitial. I would think that work would be equal to the sum of these quantities, and not the difference."

"It is a bit confusing on what 'does' work on what."

"The equation for calculating translational kinetic energy. Also how this tied in with the initial and final kinetic energies of an equation."

"I don't really understand why if the forces are perpendicular they are not doing work?"

"I'm a little confused on why we focus so much attention on the initial to final change in kinetic energy."

Explain how the SI (Système International) unit for work is related to the SI unit for force.
"The unit for work, the joule, is calculated using the force unit of newtons times the displacement in meters of an object's travel."

"They are similar in that they both have the component of Newtons, but what work has that force doesn't is the displacement in meters and is measured in joules (N·m)."

"They are both measured in joules, because they are similar forces that cause kinetic change?"

"Work is equal to the mass times the distance?"

"The SI unit for work is related to the SI unit for force because it shows us how all the units come together as one?"

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). [92%]
Pushing opposite the direction of motion: work done "against" the object (negative work). [92%]
Pushing 90° sideways to the direction of motion: no work done. [65%]
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). [57%]
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). [57%]

For the catapulted squirrel, the bungee cord force does work __________ the squirrel, which __________ the squirrel's translational kinetic energy.
on; increases.   ******************************************** [44]
against; decreases.   ***** [5]
(Unsure/lost/guessing/help!)   [0]


For the braking car, the brakes do work __________ the car, which __________ the car's translational kinetic energy.
on; increases.   ** [2]
against; decreases.   ********************************************** [46]
(Unsure/lost/guessing/help!)   * [1]


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.   ******************************** [32]
against; on.   ******* [7]
against; against.   ** [2]
(Unsure/lost/guessing/help!)   ***** [5]


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.   ** [2]
the same as.   [0]
greater than.   ******************************************* [43]
(Not enough information is given.)   * [1]
(Unsure/lost/guessing/help!)   *** [3]


Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Will we review these questions in class?" (Yes.)

"How does the angle between the force and displacement vectors figure into calculating work?" (More on this in class.)

"Will you give these equations on the midterm/quiz?" (Yes, if those equations have already appeared at the bottom of a practice quiz, or worksheet packet. Everything else, you will need to memorize.)

"Poor squirrel." (No, no, good times. The squirrel was having good times.)

"What format should we expect on the midterm?" (Four conceptual short-answer questions and one worked-out numerical problem. The study guide for specific topics covered on the midterm is now posted on the course website.)

"How has Mrs. P-dog been these days?" (She's fine, being awesome as always. Eh, squirrel, maybe not so much.)

20160924

Astronomy current events question: the "directionless" universe?

Astronomy 210L, fall semester 2016
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!)
Adrian Cho, "It's Official: You're Lost in a Directionless Universe" (September 7, 2016)
sciencemag.org/news/2016/09/it-s-official-you-re-lost-directionless-universe
Analysis of Cosmic Microwave Background data from the European Space Agency's Planck spacecraft strongly indicates that the universe has:
(A) nearly equal amounts of matter and antimatter.
(B) increased its expansion rate over time.
(C) no special preferred direction.
(D) more dark matter than predicted.
(E) undergone previous big bang/crunch cycles.

Correct answer: (C)

Student responses
Sections 70178, 70186
(A) : 1 student
(B) : 5 students
(C) : 19 students
(D) : 3 students
(E) : 3 students

Astronomy current events question: globular cluster Terzan 5 star age groups

Astronomy 210L, fall semester 2016
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!)
Liz Kruesi, "Astronomers Find Fossil Stars from the Beginning of the Galaxy" (September 9, 2016)
astronomy.com/news/2016/09/astronomers-find-fossil-stars-from-the-beginning-of-the-galaxy
Globular cluster Terzan 5 contains two different age groups of stars, as determined by analysis of the stars':
(A) brightnesses and colors.
(B) dark-matter content.
(C) speeds and motions.
(D) supernovae formation rate.
(E) gravitational waves.

Correct answer: (A)

Student responses
Sections 70178, 70186
(A) : 23 students
(B) : 0 students
(C) : 3 students
(D) : 3 students
(E) : 1 student

Astronomy current events question: Ceres cryovolcano Ahuna Mons

Astronomy 210L, fall semester 2016
Cuesta College, San Luis Obispo, CA

Students are assigned to read online articles on current astronomy events, and take a short current events quiz during the first 10 minutes of lab. (This motivates students to show up promptly to lab, as the time cut-off for the quiz is strictly enforced!)
Bill Steigerwald, "NASA Discovers 'Lonely Mountain' on Ceres Likely a Salty-Mud Cryovolcano" (September 1, 2016)
nasa.gov/feature/goddard/2016/ceres-cryo-volcano
On the dwarf planet Ceres, Ahuna Mons may be a cryovolcano that releases frigid salty/muddy water, based on:
(A) seismic data.
(B) footage of an eruption.
(C) similar geological features on Earth.
(D) samples scraped from its crust.
(E) magnetic field disruptions.

Correct answer: (C)

Student responses
Sections 70178, 70186
(A) : 11 students
(B) : 0 students
(C) : 13 students
(D) : 2 students
(E) : 3 students

Backwards faded scaffolding laboratory/presentation: inquiring about Earth's weather (with Wunderground.com 2016)

Yes, there's nothing like camping under the stars... Until the clouds roll in. Darn that weather! (Video link: "Time Lapse of Everglades Camping.")

(This is the sixth Astronomy 210L laboratory at Cuesta College, San Luis Obispo, CA. This course is a one-semester, optional adjunct laboratory to the Astronomy 210 introductory astronomy lecture, taken primarily by students to satisfy their general education science transfer requirement.)

Cloud cover is not the only weather-related nemesis of astronomers.

The wind can be problematic as well, since we are observing at the bottom of an ocean of air. (Video link: "D90 HD Test 3.")

Any turbulence that stirs up the atmosphere will affect seeing, and cause distortions in telescope images (as well as twinkling the stars). (Video link: "Atmospheric Distortions.")

And even if the skies were clear and still, astronomers have one more weather-related pitfall: condensation forming on their telescopes. This happens when the air temperature falls below the dew point, where it becomes too cold for for water molecules to be suspended in the air, and they begin to glom onto each other and collect on cold surfaces. In order to prevent this, astronomers may resort to use heaters to warm up their telescopes if the temperature falls below the dew point, but while this will keep the telescope dry, it may also warm up the surrounding air and distort seeing.

Today you'll investigate not only the weather forecasts on the Weather Underground website (wunderground.com), but also gather data from historical weather records as well.

So next time you ever get to plan a star party...

Heed the weather reports!

Unless you operate radio telescopes, which are for the most part not affected by cloud cover, turbulence, or the dew point.

TASKS (as per Slater, Slater, Lyons, 2010, with the following modifications)
Computer Setup Access the nearest Weather Underground site for your campus by clicking on the appropriate link below:
*Main campus, San Luis Obispo, CA (*.html)
*North County campus, Paso Robles, CA (*.html)
Scroll down to the "10-Day Weather Forecast," and click on the "Customize" gear icon. Make sure that the following options are checked:
*Dew Point
*Temperature
*Cloud Cover
*Chance of Precipitation
*Humidity
*Pressure
*Precipitation Accumulation Amount
*Hourly Liquid Precipitation
*Wind Speed
Click the "Customize" gear icon when you are done. Click and hover your mouse over the graphs such that a vertical line appears, so you look up specific weather data values for each hour of the day. You can also click on the left "<" or right ">" arrows to look back at recorded past weather data, or forward to see future forecast weather data.

3. What Conclusions Can You Draw From This Evidence?
Wind is caused when air rapidly moves from one place to another. Typically best telescope viewing is done when the air is calm, to minimize "twinkling" from atmospheric turbulence. What conclusions and generalizations can you make from the following data collected by a student in terms of "What season of the year (in 2009) was best suited for telescope viewing in San Luis Obispo, CA?" by analyzing which season (winter, spring, summer, or fall) has the greatest or least peak wind speed, and most or least number of weeks with more than 50% cloud cover.

Month
(2009):      
Peak Wind
Speed (mph):      
Weeks w/More than
50% Cloud Cover:      
Jan5.61.0
Feb6.71.5
Mar8.90.5
Apr11.01.0
May12.33.0
Jun7.81.0
Jul7.61.0
Aug9.21.0
Sep6.90.0
Oct7.41.0
Nov5.41.0
Dec5.41.0

Explain your reasoning and provide specific evidence, with sketches if necessary, to support your reasoning(*).

4. What Evidence Do You Need to Pursue?
Condensation is a common problem for telescopes:
You're out with your telescope on a pleasant summer evening, up late... You notice something strange. The dim stars begin to fade. The images of the bright stars suddenly have ghostly white haloes. And finally, you can barely see anything at all.
The stars are gone.
You look at the sky. Have clouds rolled in? No. All clear.
Then, you take a peak [sic] at the lens of your telescope. A thick layer of water--dew--has condensed on your lens.
You don't dare wipe the dew off the lens for fear of damaging the soft anti-reflection coatings. And with no other way to remove the coating of water, your idyllic observing session has come to an early end. All you can do is pack up and go home, with your ambitious observing plan left undone.
What happened?
Condensation. The temperature of your telescope's lens fell below the so-called "dew point." And just as when you take a bottle of cold beer out the fridge, a swarm of water molecules from the surrounding air condensed onto the glass like locusts on a field of wheat.

--One Minute Astronomer Blog, "Don't 'Dew' This With Your Telescope...," April 29, 2010 (*.html)
The dew point is the temperature at which condensation starts to accumulate due to humidity. If the temperature of your telescope (approximately the same as the ambient air temperature) falls below the dew point, condensation will begin; if the temperature is above the dew point, no condensation forms. One method to actively prevent condensation is to use built-in electric warmers to keep the telescope temperature above the dew point. A dew warmer may affect observations by creating warm air updrafts, so a dew warmer should only be turned on when necessary.

Describe precisely what evidence you would need to collect and how to collect it in order to answer the research question of, "If a robotic telescope were to make continuous observations tonight, from one hour after sunset to one hour before sunrise tomorrow, what time(s) should the dew warmer be programmed to run?" (Running the dew warmer continuously all night may needlessly create local thermal drafts that would affect viewing.) You do not need to actually complete the steps in the procedure you are writing. (For the purposes of this activity, assume that the sky will be clear tonight for observations.)

Create a detailed, step-by-step description of evidence that needs to be collected and a complete explanation of how this could be done--not just "look up the dew point forecast," but exactly what would someone need to do, step-by-step, to accomplish this. You might include a table and sketches--the goal is to be precise and detailed enough that someone else could follow your procedure.

Reference:

Physics final exam problem: tow truck vs. tugboat tug-of-war

Physics 205A Final Exam, fall semester 2015
Cuesta College, San Luis Obispo, CA

"Chevron Delo's Ultimate Tug Of War"
DeloPerformance
youtu.be/a6HUFm6FKD4

A tow truck[*] (mass 2.5×104 kg) and a tugboat pull on each other in a tug-of-war.[**] It is claimed[***] that the tugboat requires more tension to pull the truck when the cable is diagonal (10° below the horizontal), and less tension to pull the truck when the cable is horizontal. Discuss whether this claim is plausible or implausible, and how you know this. Assume that the truck's wheels are locked, and the truck is sliding to the right across the horizontal dock at constant speed. The kinetic friction coefficient for tires on concrete[****] is 0.8. Show your work and explain your reasoning using free-body diagrams, the properties of forces, and Newton's laws.

[*] rechtieninternationaltrucks.com/listings/2015-kenworth-t838-heavy-duty-wrecker-with-vulcan-v703/.
[**] youtu.be/a6HUFm6FKD4.
[***] throt-l.com/autos/surf-turf-tug-of-war-test-pits-a-kenworth-tow-truck-vs-a-900hp-tug-boat/.
[****] Raymond A. Serway, Robert J. Beichner, Physics for Scientists and Engineers with Modern Physics (5th ed.), Saunders (1999), p. 133.

Solution and grading rubric:
  • p:
    Correct. Draws free-body diagrams for both diagonal and horizontal cable cases, where:
    1. from Newton's first law is applied along the vertical direction for both cases, such that it is clear that the diagonal cable case will result in a greater (upwards) normal force being exerted by the dock on the truck in the diagonal case;
    2. from the dependence of kinetic (sliding) friction on the normal force, there will result a greater amount of kinetic friction force of the dock on the truck in that case;
    3. from Newton's first law is applied along the horizontal direction for both cases, such that it is clear that the horizontal component of the cable tension on the truck will be greater for the diagonal cable case, such that the claim is plausible.
    (It is not necessary to use both vertical and horizontal components of the cable tension force in the diagonal case to show that it would have a greater magnitude than for the horizontal case in order to prove that the claim is plausible. Also may have numerically solved for the cable tension for each case.)
  • r:
    Nearly correct, but includes minor math errors. As (p), but application of Newton's laws and/or properties of forces is slightly problematic.
  • t:
    Nearly correct, but approach has conceptual errors, and/or major/compounded math errors. May have horizontal components of the cable tensions as equal for both cases, etc.
  • v:
    Implementation of right ideas, but in an inconsistent, incomplete, or unorganized manner. Some substantive attempt at applying properties of forces and Newton's laws to free-body diagrams.
  • x:
    Implementation of ideas, but credit given for effort rather than merit. No systematic application of properties of forces and Newton's laws to the forces on free-body diagrams.
  • y:
    Irrelevant discussion/effectively blank.
  • z:
    Blank.
Grading distribution:
Sections 70854, 70855
Exam code: final7rUk
p: 9 students
r: 12 students
t: 9 students
v: 17 students
x: 21 students
y: 2 students
z: 0 students

A sample "p" response (from student 0217):

Another sample "p" response (from student 2681):

20160921

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

Astronomy 210, fall semester 2016
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.
"That smaller planets retain less internal heat than larger planets."

"The size of planets have a lot to do with the greenhouse gases and atmospheric density."

"That some other terrestrial planets used to have water on them."

"I found the 'ice giant' planets to be interesting in the fact that their interiors are warm slushy ice layers."

"Saturn's rings, because when I was younger I imagined visiting them for some strange reason."

"The Cooper Cooler effect, because forced circulation caused the water to be cooled faster."

"That there is no sudden boundary between liquid and gas in Jupiter's atmosphere. This is interesting and although I can understand it I wonder what the feeling would be like to pass from gas to liquid without making a splash."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"The polar ice caps on Mars--how is that possible when it has limited amount of water?"

"The three IAU classification criteria."

"Knowing all of the information on each individual planet. I don't know what parts are more important than others so I can't focus on what's needed."

"It's hard to remember what each planet is; I have a bad memory."

"Why pluto isn't a planet."

"How does Venus have so much clouds, but is a 'runaway planet?'"

"I need to make my own little cheat sheet to try and remember each planet's unique characteristics. I get mixed up trying to remember if each planet is hot or cold, or has atmosphere or not, etc."

"I found this reading easier to understand then past readings."

"Nothing was confusing."

"I was a little confused about how the Cooper Cooler effect works."

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 [26%]
Geologic activity, today: less than Earth [39%]
Volcanic outgassing, up until now: about the same as Earth [42%]
Heat from the sun: more than Earth [81%]
Amount of atmosphere, today: more than Earth [58%]

Identify the relative amounts of these characteristics for Mars, compared to Earth. (Only correct responses shown.)
Interior core heat, today: less than Earth [77%]
Geologic activity, today: less than Earth [65%]
Volcanic outgassing, up until now: less than Earth [61%]
Heat from the sun: less than Earth [81%]
Amount of atmosphere, today: less than Earth [81%]

Which jovian planet has the coolest interior temperatures?
Jupiter (most massive).   **** [4]
Saturn (most prominent rings).   [0]
Uranus (least active weather patterns).   **************** [16]
Neptune (farthest from the sun).   ********** [10]
(Unsure/guessing/lost/help!)   ** [2]

I believe Pluto should be a planet.
Strongly disagree.   * [1]
Disagree.   *** [3]
Neutral.   *************** [15]
Agree.   ************ [12]
Strongly Agree.   * [1]

Briefly explain your answer to the previous question (whether Pluto should be a planet).
"Since I was in elementary school it was considered a planet. I was upset that it wasn't accepted anymore but I would understand why they wouldn't consider it anymore."

"It's big-ish. It revolves around the sun even if it's orbit is less conventional. Let's include everyone."

"Pluto was the first planet that we discovered. Without this stepping stone, we would be lost, or dramatically delayed, in finding out all the wonderful things we know about our planet and its solar system. I believe this "planet" will still hold many answers for us, and we can not simply dismiss its existence by declassifying it. How disrespectful."

"It has always been known as a planet so it might as well stay that way."

"I think it should be a planet because it meets all three of IAU planet classifications including it having enough gravity for moons to orbit."

"I don't have enough knowledge or power to say whether or not anything in space should be categorized in a specific way. I don't know if it makes a difference either way."

"Pluto used to be my favorite planet, and then they stopped treating it as one. Even though it's probably not right to call it one, I wish it still was."

"I am indifferent because it doesn't really matter whether it is or is not a planet. It obviously would have been pretty scientifically supported for pluto's title of being a planet to be taken away."

"Because it is the same size as thousands of icy bodies orbiting Neptune and would force us to qualify those as planets. In addition it is neither jovian nor terrestrial in nature."

"Pluto does not meet the standard that a planet must be large enough to dominate and gravitaionally clear its orbital region of most or all ofher objects."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Can we go over more about outgassing and retention and runaway atmospheres?" (Yes, we can.)

"I learned 'My Very Educated Mother Just Served Us Nine Pizzas' to remember the order of the planets. Do you know if there is a new acronym that doesn't include Pluto that they teach now? ("Nachos." That what your mom should be serving now. #mmmnachos)

"Can we get the answers to the study guides for the quizzes? I think it would help with studying." (After going through the flashcard question packet, you can see me right after class, during office hours, or e-mail me to see if your answers are right (don't wait until the night before the quiz!) and I can "grade" your answers and tell you which are correct, and/or go over your incorrect answers with you.)

"Are there extra-credit assignments? To help those of us who want a good grade but who have test anxiety and don't perform well under pressure?" (Yes, there will be a few extra-credit assignments later this semester. But don't forget that you can drop your three lowest quizzes (out of eight total), and we will have review sessions in class for each of the midterms.)

"I blame Magic School Bus for telling me lies."

"I enjoy your presentations--they are not boring at all--you make class interesting."

Online reading assignment: uniform circular motion

Physics 205A, fall semester 2016
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.
"The sum of the total forces acting on an object must be exactly equal to the velocity squared times the mass, all divided by the radius in order for the net force to be center seeking."

"The requirements needed for uniform circular motion. The net force must be equal to mv2/r and directed in towards the center."

"Centripetal force is not another force, but rather it represents the net force that is pointed toward the center of a circular path. Centripetal force points in the same direction as the acceleration, which is also pointed toward the center of the circle."

"For uniform circular motion, the change to the velocity is its direction and not its magnitude."

"I totally get why I have to hang on to the handle of the car door while my husband drives fast around curves! Or at least now I am aware of the fact that my body is sliding off the circular motion on to a tangent to the circle."

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.
"With centripetal force, I know the forces go towards the middle but I'm confused why. Is there another force acting in the opposite direction?"

"Determining whether Newton's first or second laws apply to circular motion."

"Why centripetal force happens, and what centrifugal forces are."

"Centrifugal force, and how that relates to the subjective experience of an object being flung from the circle of motion."

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.   **** [4]
second; points to the left.   ************ [12]
second; points to the right.     ************************* [25]
(Unsure/lost/guessing/help!)   ***** [5]


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.   ********** [10]
second; points upwards.     ************************ [24]
second; points downwards.   ***** [5]
(Unsure/lost/guessing/help!)   ******* [7]


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.   ** [2]
second; points to the left.   *********** [11]
second; points to the right.   *************************** [27]
(Unsure/lost/guessing/help!)   ****** [6]


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.   ********* [9]
second; points upwards.   ******* [7]
second; points downwards.     *************************** [27]
(Unsure/lost/guessing/help!)   *** [3]


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.   ************ [12]
(Unsure/lost/guessing/help!)   ***** [5]


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.   *********** [11]
second; points upwards.   *****[4]
second; points downwards.   ************************** [26]
(Unsure/lost/guessing/help!)   ***** [5]


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.   ************ [12]
second; points upwards.   ***** [5]
second; points downwards.   *********************** [23]
(Unsure/lost/guessing/help!)   ****** [6]


Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Is there any way the reading assignments and homework reports can be due the morning just before class starts? I don't have much time to complete them the day before but I have a lot of time in the morning before class." (The online reading assignments and homework reports are due the night before class, in order to allow me enough time to read everyone's questions and comments, compile answers to the multiple-choice questions, look at which topics/problems students are having problems with, and then plan out the specific concepts and examples that will be covered in class the next day. The assignments are always open in the afternoon after the end of each class, so just plan ahead and don't wait until it's too late.)

"The textbook states that static friction is usually more than kinetic friction. When is it less than the kinetic friction?" (Maybe pushing a big stone block across a sandy beach, or scraping a hand plane across a piece of really soft wood--once you get it moving with a certain amount of force (overcoming static friction) and try to keep pushing it with that same force, it plows up the stuff underneath it and grinds to a halt (as the kinetic friction force is greater than your unsticking force for static friction). So kinetic friction forces are greater than static friction forces when the surfaces are "injuring" each other, rather than when just sliding over each other.)

"Stay true." (Word.)

"How do the fictitious centrifugal forces relate to all this? What are they?" (They're "fictitious" because these are forces you seem to "experience" when undergoing circular motion (because of your subjective inner ear sensations), but aren't in the directions that real forces are actually exerted on you. So don't try to be the object undergoing circular motion (this leads to misleading fictitious forces in wrong directions), look at the object undergoing circular motion (and only consider the real forces actually exerted it).)