Online reading assignment: energy forms and conservation, and what does the fox say?

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 energy forms and conservation.

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.

"Energy can either increase or decrease (resulting mathematically in positive or negative delta signs), but all changes on the right-hand side of the transfer/balance equation, overall, must be balanced by a corresponding amount of non-conservative work on the left-hand side."

"Gravitational potential energy--that an object that is at the top of its trajectory with all this energy stored in it ready to be transferred to kinetic energy and come plummeting down is exciting and fascinating."

"I found the examples in the blog interesting, they cleared things up a little."

Describe something you found confusing from the assigned textbook reading or presentation preview, and explain why this was personally confusing for you.

"I am still a bit confused on non-conservative work."

"Will we need to remember all of these formulas? I'm getting intimidated."

"It was mostly pretty clear."

"How to apply the work, and using all the equations for different energy forms--there are so many little things to remember."

"I'm confused about determining what to use for any given scenario. I just don't know how to recognize the which energy forms increase or decrease, but I think it is once again because I need to see some examples in class."

For the catapulted squirrel, mark whether the changes in energy are increasing (+), decreasing (-), or remain constant (0). (Assume no energy lost to non-conservative work: W_nc = 0.)
(Only correct responses shown.)

Change in kinetic energy ∆K = + (increases) [68%]
Change in gravitational potential energy ∆U_grav = 0 (remains constant) [53%]
Change in elastic potential energy ∆U_elas = - (decreases) [61%]

For the child sliding down the slide, mark whether the changes in energy are increasing (+), decreasing (-), or remain constant (0). (Assume no energy lost to non-conservative work: W_nc = 0.)
(Only correct responses shown.)

Change in kinetic energy ∆K = + (increases) [68%]
Change in gravitational potential energy ∆U_grav = - (decreases) [59%]
Change in elastic potential energy ∆U_elas = 0 (remains constant) [64%]

For Mrs. P-dog, mark whether the changes in energy are increasing (+), decreasing (-), or remain constant (0). (Assume no energy lost to non-conservative work: W_nc = 0.)
(Only correct responses shown.)

Change in kinetic energy ∆K = 0 (remains constant) [43%]
Change in gravitational potential energy ∆U_grav = + (increases) [42%]
Change in elastic potential energy ∆U_elas = - (decreases) [46%]

For the braking car, mark whether the changes in energy are increasing (+), decreasing (-), or remain constant (0), and the sign for non-conservative work W_nc.
(Only correct responses shown.)

Change in kinetic energy ∆K = - (decreases) [57%]
Change in gravitational potential energy ∆U_grav = 0 (remains constant) [68%]
Change in elastic potential energy ∆U_elas = 0 (remains constant) [55%]
Non-conservative work W_nc = - (work done against the car [39%]

Briefly describe the distinction between the ordinary language and the scientific meaning of "conservation of energy."

"In science, 'conservation' means energy is not gained or lost but only transformed. In ordinary language, 'conservation' is reducing the consumption of a fuel source."

Ask the instructor an anonymous question, or make a comment. Selected questions/comments may be discussed in class.

"The flipped classroom is different and hard to adjust to--could you post general lectures online?" (I already have, they're what you're already reading online. I don't think you want me to instead present them verbatim, as is, in class. The idea is to preview the lectures online first, so you can then ask for clarification in person, in class.)

"I'm still not fully adjusted to the flipped classroom method and I feel like when I read your lectures at home, I end up misunderstanding some aspects and learning them wrong, so when I go to class I'm a bit lost. The flipped classroom method isn't really working with me so it's just been harder to learn material correctly." (This is why this class is flipped. You would probably be just as confused after listening to a conventional lecture given in class, compared to reading the very same lecture online. But by reading it online first and giving me feedback on what you're confused on, we can concentrate on those specific topics when you come to class.)

"Kinetic energy deals with motion of the object as a whole. So does that mean, be it in a slingshot, a car braking, or a person going down a slide, kinetic energy will always be present, as long as the given object is in motion?" (Yes.)

"Where did you get the t-shirt you wore on Monday?" (The t-shirt is from shirt.woot.com...

...and is based on a Norwegian music video. If you haven't seen it already...you probably shouldn't.)