Online reading assignment: energy conservation

Physics 205A, fall semester 2019
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 reading textbook chapters and previewing a presentation on energy conservation.


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.

"The easiest concept for me to understand from the reading and slide is the fact that translational kinetic energy is directly correlated to speed, in that if speed increases, so does translational kinetic energy."

"Gravitational potential energy is the energy that an object of mass has by its position in relation to the surface of Earth measured by the height of the object and an arbitrary zero level."

"I think gravitational potential energy is the easiest energy type to identify. If an object is 2 m off the ground then it has more gravitational potential energy than if the same object were 1 m off the ground."

"The gravitational force can do negative and positive work and that only the initial and final position should be considered when solving problems. This is also why it is considered a conservative force. Also, the greater the height, the greater gravitational potential energy is."

"A conservative force is not dependent on the path between start and finish points. Therefore, these types of forces also equate to zero work if the start and finish are the same."

"Conservative force is when the work done on an object is independent from the path taken between the initial and final heights, or when it does no net work on an object on a closed path. Nonconservative force is when the work done on an object moving between two points does depend on the path of motion, as we see with force of friction, air resistance, tension, etc."

"The basics of gravitational and elastic potential energy. And how they are combined with the change in translational kinetic energy in transfer balance equation."

"When a spring is pulled back it causes the energy to be stored and once released it shoots out."

"I have learned that elastic potential energy, translational kinetic energy and gravitational potential energy all play a part in non-conservative and conservative work. As the height of where an object is increases, so does its gravitational potential energy. As a slingshot is stretched back with a rock in the sling, the elastic potential energy increases. As it is fired off, the translational kinetic energy increases, and elastic potential energy decreases."

"This specific topic was kind of a blur, not gonna lie. I understand conservative forces and how how they can store energy and later retrieve without loss, and the opposite for nonconservative energy. That makes sense, but what doesn't is the application of information into the equations."

"Not much."

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.

"I am a little unsure if the translational kinetic energy is simply increased as an object's movement or speed increases."

"Translational kinetic energy is difficult to comprehend on a practical level."

"Applying the equations to gravitational potential energy and elastic potential energy. Also need better clarification of conservative and non-conservative work."

"The transfer-balance equation and how to use it."

"I would like an example of using the transfer-balance equation in class because I am still confused on how to properly implement it into my problem-solving."

"I found the transfer-balance equation slightly confusing at first but then soon realized that its a total energy conservation equation. Other than that I did not find anything else confusing."

"I found it confusing to apply the certain types of energies to certain problems. For example, when do you use potential energy, kinetic energy, and/or mechanical energy? I understand the differences of the three. However, will a question on a test ask us to find one of these or a few of these or will we have to decide that based on the problem? "

For the woman moving upwards after being catapulted, her translational kinetic energy __________ while her gravitational potential energy __________.

decreases; increases.	*************************************** [39]
increases; decreases.	********* [9]
(Unsure/lost/guessing/help!)	* [1]

For the ball bearing being launched by the slingshot, its translational kinetic energy __________ while the elastic potential energy of the slingshot bands __________.

decreases; increases.	********** [10]
increases; decreases.	************************************** [38]
(Unsure/lost/guessing/help!)	* [1]

For the woman falling off the building starting from the edge of the roof to just before reaching her lowest point of descent, indicate the changes in each her of energy forms. (Only correct responses shown.)

Translational kinetic energy: increases. [80%]
Gravitational potential energy: decreases. [74%]
Elastic potential energy (of the bungee cords): increases. [76%]

For the woman falling off the building starting from the edge of the roof to just before reaching her lowest point of descent, the energy form that experienced the greatest amount of change (increase or decrease) was:

her translational kinetic energy.	************* [13]
her gravitational potential energy.	*************** [15]
the elastic potential energy of the bungee cords.	**************** [16]
(Unsure/lost/guessing/help!)	***** [5]

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

"How do we know when something is non-conservative and conservative?"

"For the examples above, they were cases of either an increase of kinetic energy and decrease of gravitational potential energy, or vice versa. Is it possible the have increase-increase or decrease-decrease?" (Only if there was (positive) work be done to add energy to the system, or (negative) work being done to remove energy from the system. Otherwise if there are only two types of energy and no work being transferred to/from the system, then an increase in one type of energy must be fed by a corresponding decrease in the other type of energy, and vice versa.)

"For the woman on the bungee swing, how are we supposed to know which energy experiences the greatest amount of change without numeric values?"

"Will there be a study guide for the midterm that's a little more structured on the key concepts we need to know? Or do we just have to shuffle through our quizzes and homework, etc.?" (Go through the list of example midterm questions on next week's announcements page. The idea is that the methods and concepts used to answer those examples is what you would need to apply to answer your upcoming midterm.)

"Having a hard time understanding the textbook, YouTube is my friend but also sometimes my enemy."

"Can we do an end of the year potluck?" (The final exam is basically a "knowledge potluck." Everyone should bring something.)

Online reading assignment: energy conservation

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 reading textbook chapters and previewing a presentation on energy conservation.


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.

"The work equation helps a lot when calculating forces and makes a lot of sense as long as you are able to break down which numbers you are supposed to plug into each variable in the equation."

"That an object has higher potential energy when it is at a higher elevation. That there are two types of forces, conservative and non-conservative. For non-conservative force this relates to energy that cannot be regained, like energy loss due to friction on an object."

"Gravitational potential energy will increase the higher the object is because the formula for this is mass times gravity times height. So the higher an object is and more it’s fighting with gravity thus the more potential gravitational energy. Mechanical energy is the sum of potential and kinetic energy."

"Weight force of Earth on an object is a conservative force, does work AGAINST an object, removes energy, is able to store the energy, and return it to the object by later doing work on the object. Work against an object removes energy. kg·m²/s² = joules."

"What made sense to me from the presentation preview was the two conservative energies and how work done by those two forces can be stored or later removed without loss. With respect to gravitational potential energy, I understood that an object higher in elevation had more potential energy than an object on the ground."

"It's more important to look for the change of an energy rather than just the energy."

"It seems easier to work out the equations using the final minus initial method."

"Gravitational potential energy and the change in gravitational potential energy. I also understood balancing equations which is kind of similar like in chemistry."

"There are two (so far) types of 'stored' energy, elastic and gravitational. in an ideal environment, energy is 'conserved' because it is not lost in work (done by non-conservative forces)."

"A conservative force is one that doesn't matter the path of the object it would still end up in the same place with the same amount of work."

"Conservative forces are those that are exerted on or against and objects, removing its energy and storing it for use to do work on the object at a later time, unlike non-conservative forces where the energy against an object is lost or irreversibly converted to non-mechanical forms."

"I think I understand the difference between conservative and non-conservative forces pretty well. Conservative forces can be retained and returned, for example, if someone were jumping on a trampoline, when they come down for a jump, the trampoline acts against the person and slows them down to a stop, but that energy that was working against the person is later returned as the trampoline pushes the person back up into the air and the energy lost is returned."

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.

"I found the work-energy theorem kind of confusing and would just need some more practice problems on them to fully understand it. We got a brief introduction to it last class, but it didn't stick all too well."

"I don't understand how to calculate these different types of energies."

"I understood most of this content well, but I would like to work through some example problems."

"I understand this material pretty well."

"Elastic potential energy. I am just confused by the spring strength and the stretch/crunch terms."

"What I do not understand is how gravity is a conservative energy. Isn't it acting on an object all the time so how can it be conservative?"

"Honestly the algebra of rearranging the equations tripped me up for a good 20-25 minutes. Also the differences in equations for conservative versus non-conservative forces."

"I found it difficult understanding what conservative and non-conservative forces mean; (I'm not sure if what I understand is correct)."

"Whether friction would be a conservative force or not."

"I was a little confused when I first read that an object has zero gravitational potential energy when it is on the ground and at higher elevations it has more and more. I was thinking of it backwards and now understand."

For the woman moving upwards after being catapulted, her translational kinetic energy __________ while her gravitational potential energy __________.

decreases; increases.	******************************** [32]
increases; decreases.	****** [6]
(Unsure/lost/guessing/help!)	*** [3]

For the ball bearing being launched by the slingshot, its translational kinetic energy __________ while the elastic potential energy of the slingshot bands __________.

decreases; increases.	******* [7]
increases; decreases.	***************************** [29]
(Unsure/lost/guessing/help!)	***** [5]

For the woman falling off the building starting from the edge of the roof to just before reaching her lowest point of descent, indicate the changes in each her of energy forms. (Only correct responses shown.)

Translational kinetic energy: increases. [54%]
Gravitational potential energy: decreases. [68%]
Elastic potential energy (of the bungee cords): increases. [73%]

For the woman falling off the building starting from the edge of the roof to just before reaching her lowest point of descent, the energy form that experienced the greatest amount of change (increase or decrease) was:

her translational kinetic energy.	****** [6]
her gravitational potential energy.	************* [13]
the elastic potential energy of the bungee cords.	*********** [11]
(Unsure/lost/guessing/help!)	*********** [11]

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

"The cat in the 'curling cat' video is amazing!"

"This last question of which force experienced the greatest amount of change for the woman falling off the building with bungee, shouldn't all three energy forms be experiencing the same amount of change? Or does the gravitational potential energy experience the greatest amount of change?" (Generally it is possible for three energy terms in the transfer-balance equation to experience the same amount of change (say, all increase the same amount, or all decrease the same amount), but only if there is a corresponding amount of work done on, or work done against the system. However for the woman falling off the building attached to the bungee cord, where we could assume that there is no work done by non-conservative forces, then the changes in all three energy terms (increases and decreases) must add up to zero, and so it won't be possible for all three of them to have the same amount of change, as there would need to be one decreasing energy and two increasing energies; or two decreasing energies and one increasing energy.)

"For the example with the bungee jumping women, the elastic potential energy decrease because it had its highest amount of potential energy when she was on top of the building and the gravitational potential energy decreased as she swings through the arc?" (Yes, as both the translational kinetic energy and elastic potential energy increase. Assuming that there is no work done by non-conservative forces, then the decrease in gravitational potential "feeds" the increases in translational kinetic energy and elastic potential energy.)

"I would benefit from some clarification of these examples of increasing and decreasing forms of energy."

"How to plug in information for the equations?"

"I need more time to read this section."

"If the two sliding boxes of equal mass/initial sliding speed slide across two different horizontal floor surfaces and come to a complete stop would have the same amount of work done on it by kinetic friction considering no changes in gravitational potential energy and elastic potential energy. But how is it that one box would travel farther, while the other box traveled less? Wouldn't there have to be some other force acting against the box that had the shorter sliding distance?" (No other horizontal force acts against these boxes other than the kinetic friction force. Both boxes have the same amount of work done against their motion by the kinetic friction force, but since work is force times displacement, the box that has the shortest sliding displacement must have a bigger kinetic friction force acting on it, and vice versa.)

Online reading assignment: energy conservation

Physics 205A, fall semester 2017
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 reading textbook chapters and previewing a presentation on energy conservation.


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.

"Conservative forces do work that can store and later retrieve energy without loss, and nonconservative forces do work that irreversibly loses or gains energy."

"Gravitational potential energy and elastic potential energy and translational kinetic energy are all related. Together they make up the right side of the transfer/balance equation."

"The idea of stored energy somehow makes sense to me. Taking a couple of science classes where we learned about the stored energy in ATP and how it is spring loaded in a way."

"Kinetic energy is energy in motion. Potential energy is stored energy. Potential energy is most commonly determined by the change in height. Since gravity and mass stay constant, height is the most important determinant in change."

"I understand that there are conservative forces, such as gravitational weight and elasticity, that conserve energy by storing it in the system and then applying work to release the stored energy. Conversely, frictional and dragging forces are non-conservative, and energy is lost."

"Conservative forces are forces that store energy for later use. An example of this is the weight force of Earth on an object. Potential energy is that energy that changes position to be stored for later."

"Elastic potential energy is energy stored as a result of applying a force to deform an elastic object. The energy is stored until the force is removed and the object springs back to its original shape, doing work in the process."

"The complete form of the total energy conservation equation shows the full transfers between kinetic energy, along with potential elastic and gravitational energy. They all individually can be increasing or decreasing, but they all must result in the non-conservative work term."

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 whole concept of non-conservative forces and conservative forces was confusing to me. It took me multiple readings of most of the passages in the online presentation just to get the gist of it. I understand it a little more now but it is still very confusing to me."

"I'm not exactly sure on this but when an object is in motion does it still posses potential energy or is there no potential energy and it has all been converted ot kinetic energy? can it posses potential elastic energy but still have no potential gravitational energy?"

"I'm struggling with the use of the equations for the energy types."

"I do not completely understand conservative force and its two types. Also I did not understand the gravitational potential energy equation."

"I don't understand exactly how to apply mechanical energy and know when it is conserved or when it isn't."

"Most everything in this chapter, starting from conservative and non-conservative energies, to elastic potential energy and the transfer/balance equation."

"Nothing was found too confusing."

"All I really understood this from reading assignment was how the work-energy theorem is used, and I;m still not 100% okay with how to apply it."

"Nothing was found too confusing."

"I feel like I understood this portion pretty well in that I feel confident with my answers to the reading assignment."

For the woman moving upwards after being catapulted, her translational kinetic energy __________ while her gravitational potential energy __________.

decreases; increases.	********************************* [33]
increases; decreases.	***** [5]
(Unsure/lost/guessing/help!)	** [2]

For the ball bearing being launched by the slingshot, its translational kinetic energy __________ while the elastic potential energy of the slingshot bands __________.

decreases; increases.	*** [3]
increases; decreases.	********************************** [34]
(Unsure/lost/guessing/help!)	*** [3]

For the woman falling off the building starting from the edge of the roof to just before reaching her lowest point of descent, indicate the changes in each her of energy forms. (Only correct responses shown.)

Translational kinetic energy: increases. [78%]
Gravitational potential energy: decreases. [70%]
Elastic potential energy (of the bungee cords): increases. [55%]

For the woman falling off the building starting from the edge of the roof to just before reaching her lowest point of descent, the energy form that experienced the greatest amount of change (increase or decrease) was:

her translational kinetic energy.	******* [12]
her gravitational potential energy.	**************** [16]
the elastic potential energy of the bungee cords.	******* [7]
(Unsure/lost/guessing/help!)	***** [5]

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

"If I could ask you to go over one thing in the next lecture, it would be bungee-swinging woman. Thanks!"

"The last example got me, not as comfortable with horizontal motion being mixed in with vertical motion and determining which force is greatest."

"Go over conservative forces?"

"I would like some extra discussion explaining the different forces and energies. It just seems like maybe a little much at the moment."

"Please go over this stuff."

"Could you explain a little bit more on elastic potential energy?"

"Very wordy reading assignment, read it over a few times and still can't understand it completely."

"Those equations hurt my eyes."

"Do we have to remember all of these equations?" (No, all the energy equations will be given to you, in the same format as the last page of the worksheet packet.)

"Would any object that has the potential to fall have potential energy? Does this work for objects that never actually do fall?" (Yes; but if they never fall their gravitational potential energy will just remain constant--it's like having a gift card ("potential money?"), but never getting around to use it.)

"I’m really sorry I haven’t been able to get to some assignments! I’m trying to balance everything better in my life, I hope you understand." (Just letting me know what kind of crazy is going on with your outside-of-physics life is still informative to me, and you still get completion credit for stuff like this.)

"I'm enjoying the class!"

Online reading assignment: energy conservation

Physics 205A, fall semester 2016
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 reading textbook chapters and previewing a presentation on energy conservation.


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.

"An object in motion has translational kinetic energy. The value of the gravitational potential energy will get larger or smaller depending on the height. Kinetic energy of motion can be converted into potential energy of position."

"Translational kinetic energy is in everything that has motion. Gravitational potential energy is a function of height above the surface. Elastic potential energy is energy that is a result of say, a spring or a rubber band."

"The energy of conservative forces can be retrieved without loss. Also non-conservative forces involve transfer or loss of energy when work is done."

"Gravitational potential energy depends on from where an object is dropped. The higher up an object is, the greater gravitational potential energy it has."

"As long as I know the variables in equation it should be easy."

"I think that I have really grasped the idea of conservative forces and how they first store energy from an object only to give it back. This causes gravitational and elastic forces to work in essentially the same way, and therefore have similar equations."

"Potential gravitatinal energy changes based on height and the elastic potential energy changes by the distance the spring/band stretches/contracts. I understand that these energies can be irreversibly lost to work done by friction and drag."

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.

"These sections related many equations to each other, further review will help to understand them easier."

"I am really struggling with the major concepts in these sections. Especially gravitational potential energy and kinetic energy."

"All the formulas seems very complex, all the subscripts. and the way the book is set up you only see them once. A little fuzzy on the non-conservative forces."

"I am unsure of how to figure out how gravitational potential energy works."

"Nothing yet, but I will be confused when I read it tomorrow."

"I am confused over the transfer/balance equation. Specifically, I don't understand how the kinetic, potential elastic, and potential gravitational energies have a relationship to the non-conservative work. Also why is it work zero when friction and drag are negligible?"

"I have trouble sometimes identifying where a force is. Also sometimes knowing which of Newton's laws is used."

"I am a little confused about when these conservative forces act together with non-conservative forces, because the equation is really long. I guess it's just the transfer/balance equation that confuses me."

"The practice problems at the bottom of the blog made no sense to me at all. I couldn't understand how to interrelate all of the different formulas."

"I found the different formulas a little confusing. If we could do some examples in class to clear it up that would be sweet."

"I just think applying the equations and knowing when to use them is the hardest part. Its hard to read something for the first time and see the scary equation and apply it all in my head. But that's why we go over it in class!"

"I understood the differences between conservative and non-conservative forces, but still am really confused how to get the formulas based off of them and to derive one variable out of an equation."

"There is a lot that I don't understand so the more explanation in class the better."

"I'm having trouble understanding what stored energy is. I can't really fully understand the concept of it."

"I didn't find anything confusing."

For the woman moving upwards after being catapulted, her translational kinetic energy __________ while her gravitational potential energy __________.

decreases; increases.	******************************** [32]
increases; decreases.	******* [7]
(Unsure/lost/guessing/help!)	******* [7]

For the ball bearing being launched by the slingshot, its translational kinetic energy __________ while the elastic potential energy of the slingshot bands __________.

decreases; increases.	**** [4]
increases; decreases.	*********************************** [35]
(Unsure/lost/guessing/help!)	******* [7]

For the woman falling off the building starting from the edge of the roof to just before reaching her lowest point of descent, indicate the changes in each her of energy forms. (Only correct responses shown.)

Translational kinetic energy: increases. [54%]
Gravitational potential energy: decreases. [59%]
Elastic potential energy (of the bungee cords): increases. [63%]

For the woman falling off the building starting from the edge of the roof to just before reaching her lowest point of descent, the energy form that experienced the greatest amount of change (increase or decrease) was:

her translational kinetic energy.	********** [10]
her gravitational potential energy.	*************** [15]
the elastic potential energy of the bungee cords.	************ [12]
(Unsure/lost/guessing/help!)	********* [9]

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

"How is translational kinetic energy and gravitational potential energy different than heat or light?" (Here we're looking at mechanical energy systems of objects on the macroscopic scale; heat and light are forms of energy on the atomic scale.)

"I do not understand how translational kinetic energy increases or decreases. If we look at it over an interval, does it count at the beginning or the end?" (There is both an initial KE_trans value and a final KE_trans value. But more interesting is the amount of ∆KE_trans change, and how it increases or decreases for a process.)

"How can the total mechanical energy of a moving object remain constant, provided that the net work done by external nonconservative forces is zero? How can  the net work done by external nonconservative forces equal zero?" ((a) If the energy forms only trade with each other, and not with the outside world; and (b) if any losses in energy by drag and friction work are offset by gains in energy put in by applied forces pushing/pulling the object forward.)

"More discussion on what makes a force conservative vs. non-conservative." (Good. Then we get to talk about sliding that cat across the floor. I like talking about cats.)

"Can we make one of those bungee swings from the top of the library?" (Who wants to be the first to test it out?)

"If we have more than one energy type in an equation, what do we do?" (I'll show you what we do in cases like that. Basically balance out (or try to balance out) the transfers between the different energy types. Or numerically plug-and-chug.)

"What would be the best way to memorize and understand these complicated-looking formulas?" (You're given all the equations for work and energy, in class today we'll take a closer look at using these equations both conceptually and in problem-solving.)

"I always understand how everything works when you go over it in class, and then I go back and look at how I solved problems in class and it looks like a different language. This is why the midterm is scary. :0" (That's normal when you're just getting started on the new stuff. We'll go back and review the old stuff next week that will be on the midterm, hopefully by then it will seem more familiar and less scary.)

Online reading assignment: energy conservation

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 reading textbook chapters and previewing a presentation on energy conservation.


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.

"I did not understand most of it."

"The weight force of Earth on an object is a conservative force, as when this gravitational force does work against an object, removing its energy, it is able to store this energy, and return it to the object by later doing work on the object, therefore we talk about the increases or decreases in gravitational potential energy."

"The concept that energy cannot be created nor destroyed. It is only stored and transferred into different forms."

"Elastic potential energy: when a rubber band is stretched, there is a higher energy than when it is relaxed."

"There are conservative and nonconservative forces that can act on things. Elastic and gravitational potential energies are conservative. These can be used for mechanical or useful energy."

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.

"I am trying to grasp all of these concepts I'm not really aware of what I need to work on."

"I found most of it confusing."

"How to tell if gravitational potential energy is increasing or decreasing."

"Just please lecture on the important points in this section. Nothing is too confusing a long as it is properly explained."

"I don't fully understand about gravity being a conservative force, and where or how it stores energy."

For the woman moving upwards after being catapulted, her translational kinetic energy __________ while her gravitational potential energy __________.

decreases; increases.	************************************ [36]
increases; decreases.	***************** [17]
(Unsure/lost/guessing/help!)	***** [5]

For the ball bearing being launched by the slingshot, its translational kinetic energy __________ while the elastic potential energy of the slingshot bands __________.

decreases; increases.	****** [6]
increases; decreases.	************************************************ [48]
(Unsure/lost/guessing/help!)	**** [4]

For the woman falling off the building starting from the edge of the roof to just before reaching her lowest point of descent, indicate the changes in each her of energy forms. (Only correct responses shown.)

Translational kinetic energy: increases. [65%]
Gravitational potential energy: decreases. [64%]
Elastic potential energy (of the bungee cords): increases. [59%]

For the woman falling off the building starting from the edge of the roof to just before reaching her lowest point of descent, the energy form that experienced the greatest amount of change (increase or decrease) was:

her translational kinetic energy.	********** [10]
her gravitational potential energy.	**************************** [28]
the elastic potential energy of the bungee cords.	******** [8]
(Unsure/lost/guessing/help!)	************ [12]

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

"Please help. I think 'unsure/lost/guessing/help' is the #motto today."

"Gravitational potential energy and elastic potential energy are pretty straightforward."

"I would benefit from more examples of the energy conservation problems."

"Whew--a lot covered in these section, but will be ready to dive in and reinforce tomorrow."

"Uh...I dunno about these. I understand that if one type of energy increases, the others have to decrease to compensate (since energy cannot be created nor destroyed or something like that), but I will definitely need some explanation on these."

Online reading assignment: energy conservation

Physics 205A, fall semester 2014
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 conservation.


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.

"Some forces can be classified as being conservative. These forces are able to store energy and use it later without loss of that stored energy."

"Gravitational potential energy increases as the object gets higher up and decreases as it gets lower to the ground. Elastic energy increases as an object is stretched."

"Potential energy is energy that is stored by moving to a different position; if you climb higher, gravitational potential energy will increase until you fall again. Pull an elastic band back, the energy will be stored until it can snap back."

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.

"I found all the equations like translational kinetic energy, gravitational energy, and gravitational potential energy confusing. I would not know how to solve an equation regarding these equations."

"Kinetic energy comes from potential energy, so I'm still a little skeptical on how that energy equation works."

"I think it is confusing to keep straight all the different forces and energies there are and what they do. It would be nice to have a review of the individual forces and energies and what they act on."

For the woman moving upwards after being catapulted, her translational kinetic energy __________ while her gravitational potential energy __________.

decreases; increases.	********************************** [34]
increases; decreases.	***************** [17]
(Unsure/lost/guessing/help!)	*** [3]

For the ball bearing being launched by the slingshot, its translational kinetic energy __________ while the elastic potential energy of the slingshot bands __________.

decreases; increases.	********* [9]
increases; decreases.	*************************************** [39]
(Unsure/lost/guessing/help!)	****** [6]

For the woman falling off the building starting from the edge of the roof to just before reaching her lowest point of descent, indicate the changes in each her of energy forms. (Only correct responses shown.)

Translational kinetic energy: increases. [63%]
Gravitational potential energy: decreases. [67%]
Elastic potential energy (of the bungee cords): increases. [63%]

For the woman falling off the building starting from the edge of the roof to just before reaching her lowest point of descent, the energy form that experienced the greatest amount of change (increase or decrease) was:

her translational kinetic energy.	************ [12]
her gravitational potential energy.	******************* [19]
the elastic potential energy of the bungee cords.	*************** [15]
(Unsure/lost/guessing/help!)	******** [8]

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

"What happens if this section is blank when I don't have any real questions? Do I still get credit even if I just mark that I haven't read anything and am unsure about everything?" (You get credit for 'completing' this assignment, so if the earlier sections are left blank (or effectively blank), you should leave something substantive (even if it's just describing the extent of your confusion) in the question/comment box in order to receive full credit.)

"In the change in gravitational potential energy equation: do we always use the magnitude |g|?" (Yes. The positive or negative sign of ∆U_grav comes only from the ∆y term.)

"Please go over some examples of translational kinetic energy, gravitational potential energy, and elastic potential energy in class so we could get a better understanding." (Yes, we can.)

"That homemade bungee jump looks insane! I would never try that, even if you paid me with a lifetime supply of beef jerky." (What about two lifetime supplies of beef jerky?)

"Where do you get these GIF animations?" (I extract them from YouTube using a Firefox download plug-in, and use a movie-to-GIF converter in order to deliver them to your eyeballs.)

"How hard is it to take care of your goatee? It is the most awesome goatee ever."