## 20160822

### Online reading assignment: speed and velocity

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 the reading textbook chapters and previewing a presentation on displacement, distance traveled, and average/instantaneous speed/velocity.

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 different from speed although it would be easy to view them as both the same. Velocity is a measurement of both speed and direction of an object, speed doesn't measure direction. Speed is a scalar quantity, and velocity is a vector."

"the difference between displacement and distance. Displacement is just a straight line drawn from point A to B on a travel map, whereas distance is the amount of miles that you physically drove (around every curve and through every state) on the road trip."

"Average speed covers distance traveled divided by total time. Average velocity covers covers displacement, distance from initial to ending point, divided by the time interval."

"Distance traveled is fairly straightforward (pun possibly intended) being the addition of all distances traveled in any direction over a period of time. The displacement on the other hand takes into account direction and compares the starting point to the end point, allowing for negative values. Instantaneous velocity is the rate of change in displacement at a given point in time."

"Speed is the measurement of distance traveled over a specific amount of time. Velocity is basically speed in a specific direction from a reference point. This means that if you ran a lap around a track you will have a positive speed but will have no velocity because you ended at the reference point you started from and thus have no distance traveled from your initial point that the lap began at."

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.
"just all of the different symbols for formulas that confuse me like initial time vs. ending time when you're looking at displacement. With time though I will better understand this, I just have to get used to all of the new symbols!"

"I'm slightly confused on how you can have a negative velocity. If this could be discussed in class that would be nice."

"the whole concept of instantaneous velocity and instantaneous speed. I wasn't sure how to determine whether or not the instantaneous velocity is greater, less, or equal to the instantaneous speed. I believe what through me off was the word instantaneous. On the presentation and chapter it says its just a short displacement/distance and time interval/total time, so does this mean speed and velocity can only be instantaneous if the numbers where small and/or negative?"

"There is not really anything that I did not understand. I went through and did the formulas and examples in book."

"I'm pretty confused about most of it."

Briefly describe how you would walk along a straight, level road such that your distance traveled would be longer than your displacement.
"Turning around and walking back towards the starting location lowers the displacement, but it would increase the distance traveled."

"If I walked halfway down the road, realized I forgot my phone playing Pokémon Go on that bench under the tree, then walk back to the beginning of the road. If I then walked down to the end of the road my distance traveled would be much longer than my displacement because my overall displacement would be the length of the road, but my distance traveled would be twice the length of the road"

"You would walk back and forth, since distance traveled does not take direction into account, but displacement does."

In general, average speed will be __________ the magnitude of average velocity.
 less than. ****** [6] equal to. ***** [10] greater than. **************** [16] (More than one of the above choices.) ***** [5] (None of the above choices.) * [1] (Unsure/guessing/lost/help!) ** [2]

In general, (instantaneous) speed will be __________ the magnitude of (instantaneous) velocity.
 less than. ** [2] equal to. ********************* [21] greater than. ****** [6] (More than one of the above choices.) ** [2] (None of the above choices.) * [1] (Unsure/guessing/lost/help!) [0]

In general, which of the following quantities could be negative?
 Average velocity. ************ [12] Average speed. * [1] (Instantaneous) velocity. ** [2] (Instantaneous) speed. * [1] (More than one of the above choices.) ******************** [20] (None of the above choices.) [0] (All of the above choices.) ** [2] (Unsure/guessing/lost/help!) ** [2]

An odometer measures an object's:
 displacement. [0] distance traveled. **************************************** [40] (instantaneous) velocity. [0] (instantaneous) speed. [0] (Unsure/guessing/lost/help!) [0]

A speedometer measures an object's:
 displacement. ** [2] distance traveled. * [1] (instantaneous) velocity. **** [4] (instantaneous) speed. ********************************* [33] (Unsure/guessing/lost/help!) [0]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Will the equations that we have in this class need to be memorized for each quiz/test?" (No, they will be provided to you. However, for the first quiz you should memorize the SI power of ten prefixes, and basic time definitions (1 min = 60 s, 1 h = 60 min, 1 d = 24 h). But it's okay if you do have to ask about time definitions during the quiz, as I don't want to penalize you for forgetting super-basic stuff like that.)

"It would be helpful to review some scenarios or examples in class to clarify the terms such as displacement, velocity, and distance." (Looking at the class' results on these definitions, then yes, we will need to do a brief review before we start on the worksheet and problem-solving examples.)

"What is a good way to practice these new concepts?" (Well, when doing the preview reading, just try your best, and we'll go over the new concepts in class depending on how much (more) detail you need. After we covered it in class with examples and group problem-solving, then that's what homework is for. If you need more guidance on the homework, then let me know on the homework report and we can cover that in the following class, or come into office hours, or ask questions when the embedded teaching assistant and I circulate around the class.)

"What's a good way to make-up a late reading assignment?" (Well, you can't make it up, but make sure you don't miss much more of the reading assignments this semester, as there are extra ones such that you can still get your full 100/100 reading assignment points.)

"I would like you to go over some sample questions that would resemble that on a test or quiz." (Been doing that. Will still do that. And you'll be doing more of that.)

"I really think the flipped class curriculum aids in a better understanding of the material. I'm glad it allows for more time to digest certain concepts and more preparedness in coming to class knowing what concepts you're having trouble with."

"No comment." (Uh, you just did.)

"Physics makes me feel warm and fuzzy inside." (Uh, yeah. Okay.)