June 23, 2011

Summer is the time for tenderloins

I ran into another physics professor (at the college down the street from where I live) at the awesome Naf Naf Grill a couple months ago.  We got to talking, and it turns out that he has a really cool map of all the places to get tenderloins in Iowa.

This made me think of Porky's in Des Moines, which was across the street from the grocery store I worked at during high school. Unfortunately, Porky's is no more.  Too bad, since the cruise nights were always a lot of fun.

I did find a new blog to follow: Des Loines. Their tagline is beautiful. "The Breaded Pork Tenderloin Sandwich: It's like the filet-mignon cut of pork, deep fried to perfection."

June 22, 2011

Venturi pumps, injectors, ejectors and eductors

We've had some severe weather blow through our area recently, and I've been thinking a lot about backup sump pumps.  It turns out that there is a lot of interesting physics in backup sump pumps.

It also turns out that the interesting physics is not as simple as I was hoping it would be.

This is a backup pump which requires no power (battery or otherwise) because it uses the Venturi effect to pull water out of the sump well. That sounded really interesting to me, so I sat down this morning and tried playing around with the Bernoulli equation and the continuity equation to see if I could come up with some interesting questions to ask my intro physics class next time we do fluid mechanics.

After struggling for five hours, and not coming up with anything remotely looking physically possible (47 meter pump extraction height? negative water pressure?), I've come to the conclusion that an intro level analysis (even making typical assumptions) is not possible.

After much searching through reference databases, I'm not sure I've even located a decent analysis of these pumps at an advanced level.

Since this pump is simple to conceptually understand, I'm having trouble figuring out why I can't locate a decent reference with the physics of how it works.  If anyone has seen anything on this, please let me know.

June 20, 2011

Year end reflections

This year was a real struggle for me in teaching the introductory physics (algebra based) sequence. I think there were some successes with what some of the students got out of the class, but I couldn't honestly say that I was satisfied with how the class, in general turned out.

There is no single thing that I can identify that went wrong with the class.  A whole bunch of things just lined up to make the classes what they were.  Some things were in my control, and I could have done a better job with, some things were out of my hand.

I can't rank the order in which these factors played a part of the result of the class, but here are some of the things I want to remember so that I can use them in the future.

  1. Class size

    Our algebra-based intro physics sequence is made up of 2 sections (I taught one of the sections in Fall and Winter, and both in the Spring) nominally capped at 48 students. The cap has to do with the lab space, but there was a scheduling goof-up which opened up an extra lab period in each section, so with some creative schedule-shifting we were able to enroll an extra 5-6 students in each section. The classroom only has 60 seats, so in a way, that would have been the hard cap for the class.

    It became obvious to me, only after the Fall quarter ended, that perhaps 48 students was too many in a section where I was trying to have them interactively engaged heavily with the material.  Try as I might to walk around and get them going on working on questions or examples, I could never get around to enough of the groups to get them going on it to their satisfaction.  Add to that the overwhelming attitude of "I-have-no-idea-where-to-start-so-I'm-not-even-going-to-try" which pervaded the class made it a tough row to hoe for me from the get go.

    The Winter Quarter I had a much smaller class, as many students decided they hated my style. I think I had better success in the Winter Quarter with the smaller section, but I was still trying to win over a few students who were in my section only because they couldn't get into the other. (Which they anonymously told me on their evaluations from the Fall Quarter.)  By the Spring Quarter (when I had a large section and a small section, and the students had no choice but to have me) it was obvious that the smaller section was more in tune to what was going on in class, more receptive to the interactive engagement, and to a certain degree more interested in actually learning the material.
  2. Class dynamics

    I suppose it's a bit of a cop-out to try to blame the difficulties I experienced this year on something so intangible as the dynamic interaction between the class and me and the interactions between the students.  But, this past year there was ALWAYS something lingering in the background, even before the class had decided they didn't like my teaching. My colleague teaching the other section described it as if the students were acting like it was us (the instructors) versus them (the students) in some sort of contest.  Of course, we (the instructors) see the introductory physics course as a journey that everyone (instructors and students) are taking together.  I made an effort at the start of the year to try to put the class at ease, but that lingering feeling of us-vs-them never completely left.

    At least one of the students in the larger section this past quarter identified my unease with the situation. The student commented that I let the other student's attitude affect me and the way I was teaching. There is certainly truth to that. It was really hard going into class every other day and knowing that many of the students who even bother to show up have already decided that whatever I'm going to do that day is total crap.  I was trying to balance that with actually delivering a class based on Physics-Education-Research (PER) driven methods of teaching.

    One of the points that one of my colleagues in the department had made to me was that my courses were made up of junior and senior level biology majors (primarily) who have been in lecture-only classes for the past 3-4 years.  It's the only way they think they know how to learn. I tried desperately to adjust my teaching style to match the student's comfort level while retaining the spirit of interactive engagement, but that message seemed not to be received by most students in the class.

    I talked to a colleague of mine at a conference I went to this Spring about his classes. Before I had a chance to tell him about my classes he was telling me how he was really unhappy with the class dynamics in his courses he was teaching.  I don't think this is a signal of a larger problem with students today.  Rather, I think (hope?) that occasionally you get a class that for whatever reasons just doesn't work well with you as an instructor.
  3. First day

    One of the lessons I had thought I had learned last year was to make my expectations for how the class would go very clear on the first day. I thought I had done a good job of that, but I think I can do even better. I am going to try to present actual PER data to my class next time to try to explain the motivation for the methods that we use.
  4. Organization

    I get many comments on the course evaluations about how disorganized the class seems. I think what that means is "Professor does not provide line-by-line notes for me to copy" because most of the other ways that students have asked for organization I have implemented.

    The one way in which I think I could really improve the organization of the class is if I classified what goes on the board. I often have a "mini-lecture" prepared to go along with a clicker question. Sometimes I even have examples prepared (see next item for more on example) to show to the class. What I need to do is better show the distinction between the two. If I start the "mini-lecture" with the word "Theory"  on the board (and underline it) then when I get to the example write "Example" on the board, I think it will cue the students a bit better. It seems like a simple change that I can try to see whether it helps or not.
  5. The role of "examples" - asking WHY we do a particular problem

    I don't really believe in doing too many examples in class. I mean, I don't believe that *I* should do examples in class. I already know how to do the problem. What good does it do to show students how to do the problem? They won't retain the understanding of how to work the example unless they do it themselves.

    I've explained that philosophy to students, and it has mostly been rejected by all of the classes who have heard me explain it. They always want more examples. The issue, they tell me, is that if they have not seen any examples worked by me on the board, then they have no idea how to start a problem that I give them in class to work. I had one class where (after they asked me to do more examples) I did an example and then gave the class a problem to work on their own in class and they STILL claimed that they had no idea how to start the problem. What good, then, did the example that I did for the class do for them? It ate up about 10 minutes of class time.  But they FELT BETTER about trying my problem on their own.  I don't know how I feel about this.  If I can get the students to be more receptive to interactive engagement by taking a bit of time out to be less engaging, maybe it's not so bad.

    What I do know is that I need to get better at asking students to consider why we work out a particular example or homework problem. "What did you learn by doing this?" should be a required part of the homework and example-working process.
  6. Student responsibility

    Finally, I think that there was a large lack of personal responsibility for learning exhibited by the students in my classes this year. Many of my students go to school full time and work full time or nearly full time.  Many students all over do the same. It is never easy. But, I was surprised by the attitudes of these students who somehow expected me to adjust my expectations of them based on their work schedule. I heard comments in the halls (when it was believed that I was out of earshot) that I should not expect them to come to my office ever for help or send email if they needed a hint on the homework. One student claimed that everything he needed to know should be covered in class, since he worked full time he could not be expected to ever come to my office. I agree that all the concepts needed to complete the homework should be covered in class, which they were. But there is NO WAY that I would expect that every student would UNDERSTAND the concepts deep enough to solve all the homework problems without asking for help.

    At least that student was trying to do the homework. Many of the students gave up on doing homework and a number gave up on coming to class. I changed the schedule for the last quarter so that every week they had an hour long "workshop" where no new content was presented, but the class would have the opportunity to review all the concepts we had covered that week. It actually gave the class a net increase of 45 minutes (much of which was used for working examples and homework problems) of class time per week. (15 minutes was taken out of one class period each week for a quiz, thus a one hour workshop leads to 45 minute net increase in class time.) Yet, the workshops were consistently skipped by many students.
I don't want to give an impression that I thought this was a bad bunch of students, or that I had a completely negative experience. I tried very hard throughout the year to improve what I was doing, even if it didn't always seem that way to those in my class. For me, the teaching experience is also a learning experience. I am learning all the time, and trying to always get better at it.