## 20150824

### Online reading assignment: speed and velocity

Physics 205A, fall semester 2015
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.
"Displacement (magnitude) is the straight-line distance, not necessarily the distance traveled; and speed and velocity are different. Speed is distance traveled over time and velocity is the displacement over time, which has a direction."

"Instantaneous speed is just the magnitude of the instantaneous velocity."

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 difference between distance traveled and displacement."

"There was nothing that I found confusing. But it would be nice if there was also a in-class discussion on it just to make sure that I have everything down."

"How instantaneous speed and instantaneous velocity are connected."

Briefly describe how you would walk along a straight, level road such that your distance traveled would be longer than your displacement.
"You could walk back-and-forth along the same line multiple times."

"I walk 30 feet forwards and go backwards 10 feet. My distance traveled would be 40 feet, and the (magnitude of) displacement would be 20 feet."

"If the road was a snake-like curve, the distance traveled along the road would be longer than the (magnitude of the) straight-line displacement from the beginning of the road to the end of the road."

In general, average speed will be __________ the magnitude of average velocity.
 less than. ***** [5] equal to. ******************* [19] greater than. *************** [15] (More than one of the above choices.) ************* [13] (None of the above choices.) *** [3] (Unsure/guessing/lost/help!) ******* [7]

In general, (instantaneous) speed will be __________ the magnitude of (instantaneous) velocity.
 less than. **** [4] equal to. ************************ [24] greater than. ************************ [24] (More than one of the above choices.) ************ [12] (None of the above choices.) ** [2] (Unsure/guessing/lost/help!) ******** [8]

In general, which of the following quantities could be negative?
 Average velocity. *********** [11] Average speed. [0] (Instantaneous) velocity. *** [3] (Instantaneous) speed. [0] (More than one of the above choices.) ***************************** [29] (None of the above choices.) [1] (All of the above choices.) ****** [6] (Unsure/guessing/lost/help!) *** [3]

An odometer measures an object's:
 displacement. *** [3] distance traveled. ********************************************************* [57] (instantaneous) velocity. * [1] (instantaneous) speed. * [1] (Unsure/guessing/lost/help!) [0]

A speedometer measures an object's:
 displacement. ** [2] distance traveled. [0] (instantaneous) velocity. ****** [6] (instantaneous) speed. ****************************************************** [54] (Unsure/guessing/lost/help!) [0]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"How do you denote the direction of a velocity when it isn't along a west-east path?" (Woah there--you're talking about two-dimensional and three-dimensional motion, which we'll get to eventually. Right now let's just concentrate on one-dimensional motion, which is east-west (or left-right, or up-down) motion.)