## 20180820

### Online reading assignment: speed and velocity

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 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.
"There are two types of paths: distance traveled (always positive) which is how far someone travels regardless of direction, and displacement (positive or negative) which is the straight-line distance someone travels from initial starting point to final ending point."

"that traveled distance is always greater than displacement. Speed deals with distance while velocity deals with displacement."

"The difference between distance and displacement--I know that distance will always be positive and measures all of the distance traveled in either direction or back and forth. On the other hand, displacement can be positive or negative and represents a straight line from the starting to end point an object traveled."

"That direction of motion isn't factored while measuring distance and speed while it is important when calculating displacement and 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.
"When to use the symbols given for each definition, and how I would use them. Like initial position, length, displacement, average velocity, instantaneuos velocity, etc."

"The relationships between average velocity and average speed."

"I didn't really understand the instantaneous velocity. How is it that we record multiple different positions of an object? And what exactly is approachng zero? i don't understand how to apply this final concept of the reading."

"I was a little frustrated that instantaneous speed was mentioned, but it was not explained. Maybe instant speed is equal to instant velocity? I say this because perhaps instant speed is equal to small change in distance traveled divided by small change in time. And small change in distance traveled equals small change in displacement, and the time interval would be the same. But I think instant velocity has a direction, whereas instant speed does not."

"The concepts of instantaneous velocity and instantaneous speed."

"I would like a review on instantaneous velocity vs. instantaneous speed. It would help just hearing it be talked about and explained so I can see how you explain it. I know some from calculus."

Briefly describe how you would walk along a straight, level road such that your distance traveled would be longer than your displacement.
"You walk your dog one mile to the store and one mile back to your house. Displacement is zero. Distance traveled is two miles."

"Walking back and forth along the straight road would allow the distance traveled to be greater than the displacement."

"Walk forwards and then also walk backwards because no matter the direction(s) traveled, distance is always accounted for."

"If you were to walk on a curved path from point A to point B, as opposed to a straight line, your distance would be longer than your displacement. Displacement is a vector measuring the shortest distance between point A and point B. Whereas distance is the actual path that was taken from point A to point B."

"Unless you are robotically programmed, I don't see human kind taking the shortest possible path on a straight road because of factors like crossing the road and maybe going left or right a little too much for some steps."

"Your distanced traveled would be longer if you went off the straight line, maybe if you did a loop and then continued on."

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

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

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

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

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

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"Going over the multiple-choice definition questions above would be much appreciated. Thank you!"

"Confused on average speed, average velocity, snd instantaneous velocity. Examples in class would be recommended."

"Will we need to know conversions (for example, 1 cm = 2.54 in) or will you give us a sheet of conversions for the tests?" (I will always give you the conversions that are needed to solve each question. You don't need to memorize everything, other than basic time stuff (1 min = 60 s, 1 h = 60 min, 1 day = 24 h). If you can't remember those, well, you can still ask me.)

"I would really appreciate an embedded tutor." (I would, too, but my embedded tutors from last year moved away over this summer. I've submitted a list of 10-15 more candidates for the Learning Resource Center to follow up on, so we'll see.)

"If labs are completed early with time to spare, do you ever take time to go over lecture material that is still confusing to students?" (Essentially I'm paid for the entire three hours of lab, so after you finish your lab work, feel free to stick around in the time remaining and ask me questions from lecture.)

"If you add 66 + 92 + 95 = 201, should it be 201 or 200 for significant figures or considering there is no decimal place would it just be 201?" (Since you are adding these numbers, and all of them have zero decimal places, then the answer (201) will also have zero decimal places. Note that the answer now has a different amount of significant figures than any of the numbers that went into it; this is typical of the addition/subtraction rule, where you have to keep track of the least number of decimal places (and not significant figures), and as a result may have a different number significant figures for your final answer.)

"When you are adding and one number is in scientific notation and the other is not you have to change scientific notation back? For example, if you had (4.576×103 + 350), you would have to change 4.576×103 to 4,576?" (Yes, when applying the addition/subtraction rule, all numbers must have the same power of 10, whether you would express them as 4,576 + 350 = 4,926; or 4.576×103 + 0.350×103 = 4.926×103.)