FIU Modeling Workshop – Day 11

We started today by finishing the modified lab.  After finishing, we all made whiteboards of our results and presented them.

During the presentation, a few ideas came up.  One, the groups that used the motion detector had much better results than those that measured the compression with their eyes.  Two, instead of measuring the spring constant with hanging weights separately, we could attach force sensors to the top of the car and measure the force directly during the launch.  Third, we could use a level app from smart phones to measure the angle of inclination of the track.  Four, we could use video analysis to measure the change in height (although I’m not sure if this would be as accurate as the motion sensor).

In the end, adding an inclined ramp to this lab, definitely increase the level of difficulty.  I think this would be good for a second year class, or possibly AP.  However, I think adding studying 3 forms/modes of energy in one experiment is a bit too much for first year students (especially standard level).

One of the groups placed their energy pie charts on a sketch of their velocity vs time graph, which proved to be a great way of showing the energy relationship (most of us just made a pseudo-motion map with a sketch of the track).

One other piece of advice from Jon was to make sure that you stress energy “transfer” not energy “loss” when discussing friction or other losses of energy due to non-conserved forces.

Jon also mentioned that, surprise-surprise, he had a homemade launcher instead of buying the circular metal spring.  He took a piece of 2×4 and attach two 16 penny nails (far enough apart to rest the track in between the nail).  Once the track is place perpendicular to the wood, in between the nails, he stretches a rubber band (new each lab) between the nails (over the track).  Here’s a rough sketch of a top view:

Where the yellow oval represents the rubber band, the blue circles are the nails, the grey rectangle is the track and the brown rectangle is the 2×4.  If you need to keep it level, just add a 2×4 to the other end of the track.

From there we moved to a paradigm demonstration for “potential” energy.  (I have it in quotes as we were told this name can carry with it bad misunderstandings, instead you should just call it gravitational energy or elastic energy, etc.)

Jon said that “energy” can cause pain.  So he had Chris come to the middle of the room (simulating a student from the class).  He told Chris to stick one foot out in front of him, and then asked, “Would you rather me drop this bowling ball (from waist high) or this tennis ball (also from waist high)?”  Obviously we were all cheering for the bowling ball.  Chris then asked, “Would you rather me drop the bowling ball from here (waist high) or from here (just above his shoe)?”  Chris then asked us, do you really need to do anything else to teach $\Delta {E_g} = mg\Delta h$?  Then (just to remind us of the spring equation), he suggested having 2 rubber bands, and basically run through the same thing, which rubber band would you like to have snapped on your arm, and from what distance?

After that we started working on Unit VII worksheet 2b.  Like most of these, we worked individually and then each group was assigned one problem to whiteboard.

During the board meeting we had a great discussion as to exactly how energy flow diagrams and energy bar graphs should depict the drawing.  One part of the group felt that if the type of energy is known, it should be identified (even if the interaction is outside the system); others felt that if it wasn’t part of the system, it should not be named.  I’m not sure who “won” the debate, and we basically left it up to each person to use as he/she sees fit in their class.  During the discussing, it was pretty obvious that even the experienced teachers in the room had some misconceptions about energy and what it really means to define a system.  We agreed that this is a tricky concept, and talked about to what level of understanding we should try to get our students.  Is it enough for them to merely identify the types of forces present and just that energy is entering/leaving the system, or do they need to describe the the exact means by which the energy is leaving (form of heat or work).  {My guess is that in the end it depends on your students and the standards/goals for your class}

One thing that came to mind for me was my Thermo I&II teacher who stressed that if it’s not important enough to be identified as part of your system, the interaction doesn’t deserve a name.  I’m also well aware that my students are not sophomore engineers in a Thermo class but 1st or 2nd year high school students.

We then went on to discuss our reading from last night, Making Work Work.  We did a different style of discussion in which each group wrote down 3 things they felt important within the article and then we shared our thoughts.

We finished the day by wrapping up Unit VII
What worked:
After we go the hang of them, we liked the energy bar graphs and flow diagrams
We liked the lively discussion over worksheet 3b
We liked the chaos/challenges of the last lab (cart on the incline w/spring launch)*
We felt that when Chris showed the graph he expected, we better understood what to do**
We liked struggling through the lab, it gives us a better appreciation for what I students will experience

What didn’t work:
We realize that we need to be reading the “readings” provided to the students, so we know what “they know” for each lab.
We felt that the prior knowledge requirements/level was too high for the last lab*
We felt that same lab did not have clearly defined objectives**

* and ** comments show just how split we were for the lab

Jon, Chris, and David Jones (the FIU instructor who helps facilitate this workshop) talked a little bit about the fact that the binder and online resources are not a script we have to follow, rather the tools that have emerged from numerous teachers struggling with this style of teaching.  They encouraged us to use what we liked, and modify or omit what we didn’t.  In essence they reminded us that we are professional teachers who know our students and school culture.  One of the great characteristics of the modeling method is how easy it is to adapt things to suit a given school.  As we grow in using some or all of this material, we were encouraged to share our take on it with others, so the material continues to evolve.  Their biggest hope was that we didn’t just copy the binder as is and pass it out to our students.  I think the biggest advantage to coming to this workshop is beginning to find how I might use all this resources.  For those merely reading this blog, or the others like it, I strongly recommend you set aside the time and come to a workshop.  One of the foundations for this system is that you have to experience something for yourself to truly learn it, watching or reading about it, simply don’t work.  (Yes that includes you Kahn Academy) {sorry, just had to get that in somewhere}


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