## 20170828

### Online reading assignment: speed and velocity

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 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.
"Distance traveled is always a positive quantity, secondary to it being the total distance an object travels regardless of its direction. While displacement can either be a positive or negative quantity depending on the direction the object traveled from its initial to final position."

"Distance is space traveled, always positive and displacement is the straight line from point a to point be, either positive or negative. speed is distance/time and velocity is displacement/time."

"I had a bit of a hard time understanding average velocity versus instantaneous velocity, but I think I understood it after a bit of thought. I realized that instantaneous velocity pertains to a specific instance in time. Since average velocity is the overall average it measures the displacement over a certain length of time."

"Average speed equals distance traveled divided by total time. It's always a positive quantity."

"Average speed and velocity are pretty easy to understand. Finding the average speed is done by dividing distance by elapsed time, such as miles per hour. And finding average velocity is done by dividing displacement by elapsed time."

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 still struggling to keep significant figures straight between multiplication and addition. I tend to make simple mistakes and not have an answer that's even listed on the multiple choice."

"The differences between the different velocities and speeds kind of threw me for a loop. I'm not exactly sure about the magnitudes between them and when they are greater/less than or equal to one another."

"Something I struggled with was the instantaneous velocity and speed. Specifically how they were denoted and the equation used for instantaneous velocity and average velocity."

"I was a little confused on the difference between speed and velocity until I looked at the different examples and spoke the terms out loud."

"The most confusing points for me were what is the meaning of 'the magnitude' of anything like: average velocity, displacement, etc. Also, using some of the formulas in an actual problem might be helpful to understand the concepts better."

"I am truly lost on the instantaneous velocity. This is because the symbols used I am not familiar with and I'm just lost."

"I'm confused as to whether the speedometer would measure displacement or instantaneous speed."

"I'm still not completely following the instantaneous velocity. I understand it is the small displacement over the short time interval I just think discussing it further may make me more confident."

"There are no concepts presented in the reading that I do not understand."

Briefly describe how you would walk along a straight, level road such that your distance traveled would be longer than your displacement.
"You would walk forward and then walk backwards. This way your distance traveled is more than your displacement."

"If I walk straight 10 m then go back the same way 5 m , my displacement would be 5 m, however my distance traveled would be 15 m. Is that right?"

"Honestly I know why the distance would be longer than the displacement I just cannot find the right words to describe it."

"If you were walking along a straight road, your distance traveled would be longer than your displacement if you were to walk back and forth between the initial and final points."

In general, average speed will be __________ the magnitude of average velocity.
 less than. ** [2] equal to. ****************** [18] greater than. ************** [14] (More than one of the above choices.) ********** [10] (None of the above choices.) [0] (Unsure/guessing/lost/help!) **** [4]

In general, (instantaneous) speed will be __________ the magnitude of (instantaneous) velocity.
 less than. ***** [5] equal to. ********************************** [34] greater than. ***** [5] (More than one of the above choices.) ** [2] (None of the above choices.) [0] (Unsure/guessing/lost/help!) ** [2]

In general, which of the following quantities could be negative?
 Average velocity. ******* [7] Average speed. [0] (Instantaneous) velocity. * [1] (Instantaneous) speed. [0] (More than one of the above choices.) ************************************ [36] (None of the above choices.) * [1] (All of the above choices.) *** [3] (Unsure/guessing/lost/help!) [0]

An odometer measures an object's:
 displacement. ** [2] distance traveled. ********************************************** [46] (instantaneous) velocity. [0] (instantaneous) speed. [0] (Unsure/guessing/lost/help!) [0]

A speedometer measures an object's:
 displacement. * [1] distance traveled. * [1] (instantaneous) velocity. * [1] (instantaneous) speed. ********************************************* [45] (Unsure/guessing/lost/help!) [0]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Not sure if this pertains to the preview for Monday or review for Wednesday!" (Well, both, actually.)

"How do we calculate the velocity for an object going in circular motion?" (Just worry about one-dimensional motion for now. #toosoon)

"Should we be starting a formula sheet to start memorizing, or will we be given formulas on quizzes/exams?" (Equations are given at the bottom of the archived quizzes, and on the last page of each in-class worksheet packet online. Note: there are no equations provided for the first quiz!)

"A review of the relationships between instantaneous speed/velocity vs. average speed/velocity would be helpful."

"Clarification on the relationships between magnitudes of average/instantaneous velocity/speed?"