20131105

Online reading assignment: waves

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 waves.

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.
"A wave has the ability to transmit energy in-between points but not the ability to transport any material between points."

"Standing waves are absolutely fascinating. It took me a little while to understand them, but it was definitely worth the effort. And on a side note those animated GIFs are crazy to watch, especially the last one."

"Well..the animated GIFs are cool but I'm not really understanding the concepts"

"I had no idea that whips actually break the sound barrier. I also found it interesting that the speed is directly proportional to the force [tension] and size [thickness] of the object."

"I really liked this section a lot. I felt very interesting in learning about all the different wave types and how they exist in the real world. The video on the Tacoma Narrows Bridge is crazy! Very interesting to watch and learn about. It is amazing to me that the bridge could be moved by the waves that much and not just break immediately."

"Nothing--it's all confusing."

"I found the guitar example very interesting, being a guitarist myself."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.
"I am not clear on what a standing wave is."

"Honestly, almost the entirety of this presentation confuses me."

"Aside from the book being a little cryptic at times and requiring re-reading (which is hardly new), there wasn't much that was confusing with this section."

"The equations on how they should be used was confusing to me. I'm not to sure when what equation is used for what."

"I found it confusing to discuss standing waves in terms of resonance. I don't fully understand this concept and would benefit from explanation in class."

A string of length 2.0 m has a certain linear mass density µ (Greek lower-case "mu") value of 0.0044 kg/m. If this string is cut in half, then its linear mass density µ will:
decrease.  *************** [15]
remain constant.  ************** [14]
increase.  ********* [9]
(Unsure/guessing/lost/help!)  ***** [5]

For transverse waves on a string, classify each of these parameters are being "independent" (able to be changed without affecting other independent parameters), or "dependent" (will be changed when independent values are changed).
(Only correct responses shown.)
Amplitude A: independent [61%]
Wave velocity v : independent [64%]
Frequency f : independent [53%]
Wavelength λ : dependent [70%]

For transverse standing waves on a string, classify each of these parameters are being "independent" (able to be changed without affecting other independent parameters), or "dependent" (will be changed when independent values are changed).
(Only correct responses shown.)
Wave velocity v : independent [51%]
String length L : independent [72%]
Fundamental frequency f1 : dependent [64%]

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.
"For the transverse wave speed on a string, I don't see how the speed at which the wave travels is affected by the length of the string." (It's not.)

"Do we need to understand and remember the trigonometric equations for standing waves?" (What?!? No. But you do need to know how the standing wave parameters depend (or do not depend) on each other.)

"Can you going over the independent/dependent parameters in class?" (Yes. Exhaustively so.)

"I would really like to know if you plan on keeping the flipped-classroom style for next semester." (Yes. But as you've seen so far this semester, I'm adapting and changing how to best use this style of instruction, and will plan to do so through next semester.)

"Q: What do physicists enjoy doing the most at sporting events? A: The Wave."

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