Unit 7 – Blog Post (Energy)

What is Energy?  A significant amount of time spent discussing the fact that no one really knows what energy is, but that we are all familiar with its use in everyday language as well as in science class.  It is a pervasive topic central to many aspects of science, yet is elusive in developing a pure definition that all can agree upon.  In typical fashion, we started by generating a broad list of ideas related to energy and then attempted to narrow down.  Since energy is not “tangible”, we used an analogy to help describe it.  Energy could be like “currency”; $100 could be represented as a bill, as a balance in a bank account, as an IOU, etc.  All of these are different representations of a particular amount of something, but what is most useful as an analogy are the examples in which there is nothing material (a balance in a bank account, IOU, etc) as energy itself is immaterial.  In all, we spent a lot of time discussing energy, but not really sure how it helped build the concept of energy in terms of a model.  This is something I will need to develop more. 

1^st rule:  All energy is STORED energy, you must name where it is stored (or how it is stored)

Visual Representation:  Pie charts were utilized to help provide a visual representation of energy, especially related to conservation of energy; a well documented and often discussed topic that is pervasive in all of science.   

How do we know energy is stored in a spring?  After a quick demonstration, we discussed how the spring can cause an object to be propelled when it returns to its original shape.  We then performed an experiment in which we determined the relationship between the force acting on a spring and the resulting displacement.  After graphing the relationship, we took “a broad leap” and said that the area under the force-displacement graph must be the energy stored in the spring.  I honestly had difficulty with this approach as there wasn’t any clear understanding presented as to why the area under the F-D curve represented anything.  Personally, I feel this is a huge issue as energy is central to all of physics and a major factor in most all other sciences.  I felt a bit let down here, and feel I will need to spend much more time trying to justify this with my students.  We found that the force could be represented as F = kx and that energy could be easily found as the area under the curve; EPE = ½ k x^2. 

Development of Kinetic Energy and Gravitational Field Energy:  Using our relationship for energy stored in a spring, we then set about determining how the speed of an object depends on the energy stored in the spring, as well as how the height an object acquires depends on the energy stored in the spring.  These activities led to relationships from which we could develop the equations for Kinetic Energy and Gravitational Field Energy.  Although our groups worked very accurately and efficiently, it was clear that errors were too great to accurately develop these relationships.  This is a bit troubling, as students will likely be less accurate then the physics teachers performing these activities.  Nonetheless, we developed that KE = ½ mv^2, and GFE = mgh. 

  

We also attempted to incorporate friction into our energy model by looking at how the distance an object slides was related to the energy stored in the spring.  This one yielded even more inaccuracies then the others.  No relationship was able to be derived that matched the actual models.  From a practical standpoint, it appears there are just too many variables that must be controlled in order to obtain meaningful data.  L 

Worksheets:  We spent lots of time working on worksheets that used the visual representation of energy to help guide students through problem solving.  I found these problems, and the use of visual representations to solve them, to be time well spent! 

Practicum:  We attempted to drop an object attached to a spring so that it just touched a tin foil cap placed over a cup on the floor below.  This proved to be a rather challenging practical, but did a nice job of connecting the different energy topics developed through this unit. 

How I feel about it:  Personally, I think the energy unit needs to be developed a bit more for the workshop experience.   This is not to say the unit is not developed enough for student delivery, but we appeared to rush through this topic a bit too quickly in the workshop.  I was uneasy, at first, about the loose use of vocabulary in the beginning stages, and began to question whether or not modeling strategy was the best way to go.  Over time, I began to understand, and at least partially accept, the reasons for loose vocabulary.  I feel that I will need to spend significant time developing how I will deliver this unit in order to have it be meaningful to my students.  I do feel, however, that the experiments used to develop kinetic energy and gravitational field energy were useful and insightful.  I question, however, how much they will help with student problem solving. 

How I intend to implement:  As stated above, I will need to work on the pacing and depth of coverage for this unit before I feel comfortable implementing it in a modeling format.  This is such an important topic in physics that I want to make sure its delivery provides the student with the full insight that this topic deserves

. 

Difficulties I see coming:  I think students will be able to handle the visual representations of energy without much difficulty, but will still struggle somewhat with the set up of the more challenging problems.  However, I am hopeful that, with repeated practice and white boarding, more and more students will begin to understand this powerful topic and how to apply it to everyday scenarios