Tuesday, July 5, 2011

FIU Modeling Workshop - Day 6

We started today by finishing our whiteboard summaries of Ch 2 from Aron's book.  Since I didn't go into detail on the Day 5 post, I'll omit them here as well.

From there, we wrapped up Unit III with some feedback to Jon and Chris:

What worked:
  • The worksheet "stacks of kinematic graphs" - we felt that it was a great tool for helping students convert from one type of kinematic graph to another.  Chris mentioned that if/when you have students whiteboard this, to make sure that they display the graphs vertically.
  • Worksheet: Speeding up/slowing down - we liked that this allowed us/students to predict what they thought would occur, then later them seeing the results. 
  • We liked that there were multiple labs that were short, as you could get more hands on time, but not use multiple days to do different activities.
  • We liked seeing the graphical proof of kinematic equations
  • We liked the reading from Aron's book, especially the misconceptions he mentioned, and tools to help overcome them.
What didn’t work:
  • We said that we would like more insight into the "mechanic" of implementation the modeling cycle
    • What does the day to day flow look like
    • When do learning objectives come into play (some are at schools that must display the objectives for that day's lesson at the start of class)
    • Pacing of course
  • Some of us that aren't familiar with the content want more time to complete activities, and we also recognize that we need tools to overcome what we see in the workshop; some people are done with nothing to do, while others are struggling to keep up.
  • Some asked, "What to do if we don’t have loggerpro/equipment?"
  • One other thing we liked in the first cycle that didn't occur here was the division of Labor/variation of control variables.  {I'm not sure how you would fit that in, but that's what came up in discussion}
 {To those in the workshop (merely reading) that want to see the pacing of a class, one website I found was Mark Schober's Website.  Another great blog that you might find useful is Action-Reaction, one especially nice feature is that he organized his blogroll for different subjects (I'll try to get to that at some point).}
Miscellaneous Questions:
  • How often do the students need to do formal lab reports, and how do those "Work?"
  • As already mentioned, what are some ideas for extensions of labs for “faster” students
For the first question, Jon referred us to some of the resources at the beginning of the modeling binder (here, here, and here).
For the second question, Jon mentioned that he often splits up the groups that are done and have them help the groups that are going slower.

One other point that came up, was that if you need help keeping everyone engaged, assign each person in the group a roll. {When I need to do this, I use "Leader," "Secretary," "Technician," and "Gofor."  The leader in is charge of making sure the group is on task.  The Secretary is in charge of recording all necessary information/procedures/equipment/etc.. The technician is in charge of running the actual experiment.   The gofor (some call it the Yeoman) is the person in charge of "going for" stuff.  He/she gets the equipment at the beginning, is in charge of cleaning up at the end, and the assistant for all other jobs.}

One other conversation that came up was to make sure that everyone in the group knew one anothers' names.  Jon mentioned that he was surprised how many problems could be avoided if they knew that one simple fact.  He makes it a point to quiz students each others' names at beginning of new lab groups.

When Chris got a chance to address the question about objectives, he said he often uses some of the resources from the modeling curriculum to make review's

Kelly O'Shea has a blog that I love, which focuses a great deal on Standards Based Grading.  (One oversimplification of SBG is you report grades based on learning objectives of the unit. ) (Here are her objectives for Honors Physics, by the way).  When I asked her when she reveals her objectives to her students, she said:
Usually try to hand them out at the start of the unit. I would say few students look at them before they are preparing for an assessment. Some probably don’t look at them until they get the test back and look at their scores.
Jon mentioned that he often uses the provided Unit Objectives sheet to create a review.  Chris said that he often has the 3 ring-binder out when groups are whiteboarding, and often asks questions right out of the teacher notes (post lab discussions especially)

This was a lengthy discussion, but some great ideas came out of it.  From there we began Unit IV:

Jon began the unit by asking us to describe the motion of the following event:
{He tweeked the activity as we do not have student desks, what he said to do in the classroom was to have a student sit at a desk that everyone can see.  Push the desk so that it starts moving at near constant speed, and then stop pushing.}

We were to describe the motion using our 4 tools (written description, motion maps, kinematic equations, and kinematic graphs (x vs t, v vs t, and a vs t).  {We were to make those tools describe the motion from before it started moving until after it stopped.}

After we were done with our individual answers, Chris shortened the process by just asking individuals to share their ideas/draw their graphs on the board.  {I'm guessing that he was trying to make up for lost time due to our lengthy discussion earlier, and would do this through whiteboards, but I could be wrong.}

During this process, students often want to jump to why the objects are doing what they are doing.  Which leads to a discussion on forces.

From there, Chris said that he then does a mini-lecture on contact forces (forces caused by to objects being in contact) and fundamental forces (Gravity, Electro-magnetic, Strong, and Weak). {He said that he doesn't get into Normal and Friction forces at this point, but I might.  I'll have to think on this some more.}

From there, he makes use of a hovertoy (examples here and here, or make your own similar by hot-gluing the top to a "sport-top" water bottle to a CD, and slipping an inflated balloon over the cap. If your school has an airtrack, that would obviously work as well. ).  With the air turned off, push the puck across the table.  Then turn on the air, and push the puck.  Ask the students what is different about the two trials.  Guide the discussion until they realize that, for the whole series of demos, no force acting on the object leads to no change in motion; force applied leads to a change in motion. "No Force, No Change."

{Newton's first law, but like much of modeling, focus on the concept not the name.  Chris mentioned that he steers the conversation away from the term inertia, and instead focuses on the terms "balanced" and "unbalanced" forces.}

From there, Chris introduced Free Body Diagrams (FBD), in which you show the forces acting on the object (or system).  He started with a FBD for the puck resting on the table:

The circle/dot in the center represents the object, the arrows represent the forces acting on the object.  Chris said it was up to you if you wanted a convention such as all arrows point away from dot, or arrows point to show how the force is acting (Push-inwards arrow, Pull-outwards arrow).  The convention used in modeling for the name of the force is the numerator is the acting object, the denominator is the object in question.  So the two forces here are the force of the table on the puck $F_{T/P}$ and the force of Earth on the puck $F_{E/P}$ (AKA the force of gravity/ weight of the puck).  If need be, remind students that the earth is the object that creates gravity, not that gravity is an object itself (Thus $F_{G/P}$ would be incorrect).

{By the way, when I was a wise-a$$, acted like a student, and said that the puck is resting on the table, so the table can't be pushing up, Jon went into the closet, found a bowling ball and rolled it to me.  He told me to lift the ball and hold it shoulder-high at arms length.  Then asked if I'm pushing the ball to keep it at that same height. Touche Jon!}
{By the way, a bowling ball is another cheap prop you can use for the earlier part of the lab.}

He then showed a FBD for the puck at the instant he first pushed it:

The added force is the force of "your" hand on the puck $F_{H/P}$

From this discussion, Chris had us work on Worksheet 1, and then had groups whiteboard answers. {My only concern with this is that many of these problems get into 2D FBD's.  I'm not sure if I want to get to that before I've really had the students do any hands-on with forces}

Chris mentioned that this worksheet does a great job of bringing out student misconceptions about forces.  Most students get stuck, so instead of whiteboarding answers, for this problem, he has them whiteboard their questions about the worksheet.

At this point, we moved on to the paradigm demonstration: Dropping a bowling ball from shoulder height.
We again went through the usual questions, however, Chris added one more to the mix:
What do you notice? What can you measure? What forces are present? What can you manipulate?
We then created the purpose: To determine the graphical and mathematical relationship between the force of the earth on the object and mass.

We were then thrown a curveball for the experiment, we were given a Vernier Dual Range Force Sensor (Jon mentioned that spring scales work just fine) and some standard masses, and guided to plot mass vs Force.  As we saw that the data made a straight line, we could find the slope of that line. 

Each group then whiteboarded their results.  About the time the groups were getting lazy with the presentation (since we all had approximately the same numerical results), Chris threw out a question, "What is the connection between the slope of your line and dropped bowling ball from the start of the lab?"

For the groups that plotted Force in units "N" (which are, as of this point in the process, possibly unknown units) vs mass in kg, we found that the slope was eerily similar to the number we measured when finding the acceleration of object dropped (picket fence and rubber ball over motion detector) in the previous units.  That acceleration describes the acceleration of the dropped ball.  If all the groups used grams (which are the units printed on most standard masses), guide them through questioning to the value of slope with mass in units of kilograms.

Chris also noted, that making the connection between $N/kg$ and $m/s^2$ will payoff when Electric fields come up later in the year. {Obviously, this point will need to be reinforced throughout this unit and others for the students to remember it during E&M.}


  1. This is very helpful - the level of detail, the pros and cons. I've attended (and am attending) a modeling workshop, but there is so much to take in. Your record of teachers' questions and answers about the nuts and bolts of implementing modeling is something I'm sure I'll go back to once the year begins.

  2. Thanks Noah, If you see anything I'm missing, don't hesitate to let me know. I know I've missed things along the way. With the amount of info to which we are exposed, I understand why it's 3 weeks. To me, as scary as is looks to write it, 3 weeks is almost too short.

  3. I couldn't agree with you more Scott. It could definitely been longer. I actually went through Physics Nerd withdrawl last year when it was over. These posts are great! I so wish I had taken better notes last year when I took the workshop. I'm going to use these posts to review this year. Great job. Glad you are enjoying the workshop.

  4. Thanks Bryan, if you see anything you think I should add, please don't hesitate to write it. I'm very interested in others take on the workshops. I'm sure there are things I've missed along the way.

  5. Scott, you mentioned something in this post about wondering what to do with the students that are done a bit faster, one of the options that came up in our workshop were the challenge problems from Schober. They're certainly deep enough that even the most advanced kids are going to need considerable time to solve them. Also, there was a recommendation that if you're boarding up some problems, and you have a group done early, to have them board up an intentionally wrong, but defensible solution, and then during discussion they need to push their classmates to correct them.

  6. Thanks for the great ideas Harding!

  7. Hope you don't mind, Scott, but I'm going to dialogue with your blog this year as I too go through this for the first time. I'm going off sequence from the ASU stuff, and following the trend of some others CVPM>BFPM>UAPM>UBFPM. I established in CVPM that being at rest is a just one of many possible constant velocities. We're spending some time at the beginning of BFPM diagramming various situations for objects at rest (incorporating some 2D as well from Force tables and spring scales and strings on lab posts, I think I tricked them into convincing me of the validity of tip to tail vector addition today to determine net force in 2-D situations). Anyway, the worksheet you reference here, worksheet 1, I gave it to them on day two-ish of the model, but only asked that they identify the situations where they thought CVPM applied. I'm hoping they'll paint themselves into a corner of "we've established that forces are balanced for objects at rest, being at rest is CVPM, so perhapds BFPM provides the theory behind all CVPM." At least that's how it sounds in my head right now, hoping they'll buy into it.

  8. Harding, to me it sounds interesting, let me know how it plays out!