## 20170830

### Online reading assignment: motion

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

Students have a bi-weekly online reading assignment (hosted by SurveyMonkey.com), where they answer questions based on reading their textbook, material covered in previous lectures, opinion questions, and/or asking (anonymous) questions or making (anonymous) comments. Full credit is given for completing the online reading assignment before next week's lecture, regardless if whether their answers are correct/incorrect. Selected results/questions/comments are addressed by the instructor at the start of the following lecture.

The following questions were asked on 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.
"Velocity is the derivative for position and acceleration is the derivative for velocity. The slope for position over time is velocity and the slope for velocity is acceleration on the graph. Knowing which equation to use for specific situations is crucial."

"How we can get acceleration through calculus formulas such as derivatives of velocity and vice versa through integrals. Displacement, velocity and acceleration are highly related and from knowing one formula we can find each equations and values."

"Integration gives an area under a curve, while differentiation would give the slope of a curve. There are two types of slopes: tangent for instant velocity and acceleration, and chords for average velocity and average acceleration."

"HPosition, velocity and acceleration are connected with a 'calculus chain of pain.' In the chain of pain moving left is caused by differentation and moving right is caused by integrating. There are five motion equations needed for the acceleration of motion. Graphs can also represent motion."

"How to generally solve physics problems. It roughly says: Read through and pick out the known, given, inferred quantities, and identify remaining unknown quantities. Do this, THEN you choose which of the 5 constant acceleration equations you will use to solve the problem, taking into account which pieces of information you have and which information (quantities) you need to find."

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.
"What I found confusing was how/when the average speed and magnitude of average velocity can be equal."

"The graphical relations charts confused me a lot. I'm not sure what any of it means."

"The different kinematic equations started to confused me because I'm mixing up what they do. I just need more practice with them."

"I don't understand tangent or chord slopes and the 'chain of pain.'"

"So few letters, so many subscripts."

"I couldn't find anything confusing as I am somewhat familiar with most the material."

Briefly describe the difference(s) between a chord slope and a tangent slope on a graph.
"There are two types of slopes, tangent vs. chord. These correspond to the two different types of velocities and accelerations (instantaneous vs. average)."

"The tangent slope is the slope at a certain point on the curve, while the chord slope is the slope between two points on the curve."

"A chord slope hits two points of a graph while a tangent only hits one."

"Shape?

Mark the level of your exposure to (basic calculus) concepts of derivatives/integrals.
 None at all. ****** [6] Slight. ************ [12] Some. ****** [6] A fair amount. *************** [15] A lot. ******** [8]

Indicate how each of these quantities are determined from kinematic graphs.
(Only correct responses shown.)
Displacement ∆x: area under a vx(t) graph. [68%]
Position x: (None of these choices.) [36%]
Change in (instantaneous) velocity ∆vx: area under an ax(t) graph. [53%]
(Instantaneous) velocity vx: tangent slope of an x(t) graph. [66%]
Average velocity vx,av: chord slope of an x(t) graph. [72%]
(Instantaneous) acceleration ax: tangent slope of a vx(t) graph. [55%]
Average acceleration ax,av: chord slope of a vx(t) graph. [51%]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"What would be a good way to prepare for the quiz, and what kind of questions should I expect?" (The first quiz will be very similar to last semester's quiz that you used scratchers to practice with. Whatever you had problems with on that should diagnose what you need to study more to prepare for next week's quiz.)

"How many problems similar to the ones in the book can we expect on a quiz/exam? Would you consider your exams to be more based on archived quizzes we find online, or is it a fair mixture?" (I would say based more on the past quiz and exam questions (which themselves are loosely adapted from the textbook).)

"Will we be able to bring a handwritten equation 'cheat sheet' to tests?" (No. All equations and constants will be given to you on the quizzes and exams (except for the first quiz).)

"I'm so lost on the whole graphing thing. More lost than I previously thought."

"Can we work through the chain of pain? I'm starting to get it...I think, but I could use a lot more practice."

"Uh, chord slope?"

"From my understanding, is a chord similar to the secant line?" (Wikipedia says, "yes.")

"I would like more lecture in class and less example questions."

"I just want examples for what kind of problems Ill be seeing on exams and quizzes from these chapters."

"I am most confused about the symbols for describing velocity and acceleration. Why is there an arrow above x and v and not t?" (Short answer: even though time has a direction, we can't go backwards in time. Long answer: it depends.)

"Is there a derivative to acceleration?" (There is--it's called jerk. Just as acceleration will cause an object to go from no speed to a fast speed, jerk will cause an object that is not accelerating to suddenly accelerating. There are even higher derivatives past jerk (snap, then crackle, pop, lock, and drop), and on the other side, there are integrals of position (absement, absity, abseleration, abserk, etc.).)