## 20180822

Physics 205A, fall semester 2018
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 the reading textbook chapters and previewing a flipped class presentation on (constant acceleration) 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.
"I have a better understanding about displacement and how it represents the objects initial starting point to the ending point. I understand how the magnitude of displacement is the shortest distance between the initial and ending point. I also will memorize the chart and the acceleration formula."

"The sections in the book confused me. However, what I took from this lesson is that average speed and average velocity magnitude can in fact be equal if your are driving a straight path. By definition average speed = (distance traveled)/(time elapsed), where as average velocity = (displacement magnitude)/(time elapsed). So if you're driving in a straight line then your (displacement magnitude)/(time elapsed) would not differ from distance traveled)/(time elapsed)."

"To go from position, to velocity, to acceleration you take the derivative. If you do the exact opposite, taking the integral, you can go from acceleration, to velocity, to position."

"The graphical relations to get to average velocity and acceleration from position and instantaneous velocity respectively. Also how to move from position to instantaneous velocity to instantaneous acceleration using tangent slopes."

"The calculus relations chart--calculus is not a new subject for me, so the concept of integrating to go one way and deriving to go the other was familiar and almost comforting to see."

"I think I understand the 'Chain of Pain' and how you get an answer by following the flow chart. Conceptually I don't think I'm there yet but hopefully will be soon."

"I was intimidated by this (and still am), but from what I understand, we are utilizing derivatives to calculate position, acceleration, and velocity. I think that the lecture will help clear a lot of things up for me."

"The thing I most found confusing was when the graphical relations were mentioned. The tangent slopes and chord slopes were the most confusing in this reading. How you get from position, average velocity and average acceleration using chord slopes or tangent slopes confuses me."

"The last sentence in the preview made the most sense. I wish it was the first: 'The most important part of solving physics problems will be reading through and picking out the known/given/inferred quantities, identifying the remaining unknown quantities, so then this will help you determine just equation(s) you should be using for a particular situation.' I finally understood something."

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.
"While I am great with calculus, the 'Chain of Pain' chart is very confusing. I am not really sure what a chord slope is and I am just lost on the equations with all the different symbols."

"Calculus has never been my strong suit, but I love physics, so I think that once I have a lecture on the material and see some examples done in class and do some more on paper, I will have a much clearer understanding of it."

"Something that I feel I could use a better explanation of is the 'Chain of Pain.' I'm not sure exactly how you want us to follow it."

"The difference between chords and tangents."

"The 'Chain of Pain?' What was that all about? Chord slope? Tangent slope? Didn't make sense to me. Also what was the calculus relations chart about?"

Briefly describe the difference(s) between a chord slope and a tangent slope on a graph.
"A tangent line touches the graph at only one point while a chord touches two points on the graph. "

"A chord slope connects two points on a graph, and it can be used to find the average slope of the graph between the two points. A tangent line touches a point on a graph and can be used to calculate the slope of the curve at that point."

"Chord slopes and tangent slopes have two different types of velocities and accelerations (average and instantaneous)."

"The chord slope connects two different points on the graph, and if those points get closer and closer to a single point to find the slope, it becomes a tangent slope set a single given point."

"I know that a tangent slope touches the graph in one spot--that's about all I remember... :["

Mark the level of your exposure to (basic calculus) concepts of derivatives/integrals.
 None at all. ************  Slight. *******  Some. *******  A fair amount. *************  A lot. ***** 

Indicate how each of these quantities are determined from kinematic graphs.
(Only correct responses shown.)
Displacement ∆x: area under a vx(t) graph. [39%]
Position x: (None of these choices.) [25%]
Change in (instantaneous) velocity ∆vx: area under an ax(t) graph. [43%]
(Instantaneous) velocity vx: tangent slope of an x(t) graph. [43%]
Average velocity vx,av: chord slope of an x(t) graph. [41%]
(Instantaneous) acceleration ax: tangent slope of a vx(t) graph. [48%]
Average acceleration ax,av: chord slope of a vx(t) graph. [52%]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"All of this graphing and the equations are just jumbled up for me, is there a better way to approach or understand them? i really need help with the the 'Chain of Pain.'"

"How the heck do I read the 'Chain of Pain chart?' Where/how do the arrows start/stop?"

"Please go over the graphs in regards to tangents and chords and how they relate to the equations and graphs."

"We need to go over this in class. I have not done calculus since senior year of high school!"

"Just hoping that the lecture notes and practice problems in class will help clear this section up for me a bit!"

"I wasn't able to get my hands on the textbook for this reading assignment; and I did not find the presentation to be helpful for this assignment."

"When is the latest that students should acquire their textbooks?" (Right around now, especially since the presentation slides only just summarize the details that are explained more fully in the textbook. There is a reserve copy of the textbook available at the library.)