20131029

Online reading assignment: static fluids

Physics 205A, fall semester 2013
Cuesta College, San Luis Obispo, CA

Students have a 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 reading textbook chapters and previewing a presentation on static fluids.

Selected/edited responses are given below.

Describe something you found interesting from the assigned textbook reading or presentation preview, and explain why this was personally interesting for you.
"Static fluid doesn't flow, but its particles are constantly moving."

"Buoyancy is dependent on the density of the fluid and the volume of the object--it seems like a straightforward topic."

"I really liked the picture of the Styrofoam® cups that were under pressure."

"I find it interesting that the increase in elevation ∆y has a corresponding decrease in pressure ∆P and vice versa."

"I enjoyed learning why snowshoes work, mathematically speaking."

"I found it pretty interesting that it's a lot easier to float in high salinity waters."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"Why does the buoyant force on an object depends on the density of the fluid?"

"Buoyant force was confusing because I don't understand why you use the submerged volume but not the object volume."

"I am having a hard time discerning whether or not atmospheric pressure at sea level would be measured as an absolute or gauge pressure. It seems like both, but I'm at a loss. Also these units are confusing, 'nuff said."

What is the numerical value for atmospheric pressure (Patm, at sea level), in units of Pa?
"101,325 Pa."

"1.013×105."

"I'm not sure how to do this. Please explain."

"101.3 kPa."

"101.3 Pa."

"1 atm."

For the question above, the numerical value for Patm is a(n) __________ pressure value.
absolute.  ************ [12]
gauge.  ******************** [20]
(Both of the above choices.)  *** [3]
(Unsure/guessing/lost/help!)  ***************** [17]

To three significant digits, what is the numerical value for the density of water, in units of kg/m3.
"1,000 kg/m3."

"1.00×103 kg/m3."

"I'm not sure how to start."

In the bouyant force equation (9-7), p. 328, the Greek letter ρ ("rho") refers to the density of the:
submerged object.  ****** [6]
fluid the object is submerged in.  ******************************* [31]
(Both of the above choices.)  ******** [8]
(Unsure/guessing/lost/help!)  ******* [7]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"I still don't like the flipped class format, it doesn't make sense when I look at the book and I get frustrated. Also in class, you go too fast and I usually have no idea what you are talking about because I'm still trying to process the beginning of whatever you are explaining."

"With all of the formula manipulation in the book, it is hard to follow what is actually happening. But I don't know how important that is."(Consider that deep background. Concentrate on how to apply these equations to model real-world applications of these phenomena.)

"What do they mean by static fluid? Like a fluid that is all the same?" (No--that would be a uniform fluid (which is already assumed here). By 'static,' a fluid that is stationary is meant. Later we will discuss 'dynamic' fluids, where the fluid is flowing (but in specific situations where it is steadily flowing).)

"I really liked that Styrofoam® cup example. It took me aback for a second and gave a face to the relationship between volume and pressure in the 'energy density conservation' equation." (Yes, but from an energy conservation approach.)

"I would love to know if I am getting the correct answers to these online reading assignment questions. Is there any way to post answers before/after class as study material?" (This blog. The blog that I show you at the start of every class: http://waiferx.blogspot.com.)

"I’m not one for buoyancy, but hey, whatever floats your boat." (Or sinks it.)

"Kill me now?" (I'm not ready yet. Wait until the second midterm, if you can.)

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