Simpsons and prone bikes: Pre-class overheads (October 21 – 25)

This week, we continued talking about conservation of energy and the work-energy theorem and began to talk about power. Something I did not appreciate when I first learned these concepts was how power-ful they really are. Some of the problems we did in lecture include estimating the fuel efficiency of a car and estimating how much food you should eat to maintain weight. With a few basic assumptions, conservation of energy gives you a fairly simple method to obtain a fairly precise answer to these complex questions.

Over the past weekend, I found a site which archives Simpsons clips with science references, for use by science teachers. In the first class of the week, we began the lecture with the curling clip. In this clip, Homer throws the stone much too hard. Marge sweeps the rock off of the curling sheet, across the pavement and through the concession, and finally back onto the sheet, where it comes to rest on the button. The connection to physics is made explicit by Principal Skinner: “That stone is coming in like a rocket! …  Someone has to convert that kinetic energy back into potential.” While the clip was playing, I observed the students and saw that engagement was very high. However, once the video was done and the instructor attempted to initiate a discussion, no one was clamouring to volunteer their thoughts. When one student did volunteer, I do not think that they had the attention of the class when they commented. (This was exacerbated by technical difficulties with the microphone, which caused a delay between the video and the comments.) Even if more students had wanted to comment, I feel that the video may have been tough to comment on, because once it finished and was not on screen anymore, there was nothing for the commenter to refer to.

2048px-prone_bikeIn the Thursday class, we had a photo of a prone bicycle. To the photo, the professor added the queuing phrase: Why would you do that? The three-word answer that was immediately volunteered was: “Reduce air drag.” This connected well with a problem from in class which shows that air drag is more important than rolling friction when determining the work needed to ride a bicycle. If the goal of the photo and queuing phrase was to allow them to analyze a new situation and connect to the course material, then we succeeded. If the goal was to try to bring students’ prior knowledge into the class, I’m not sure if this succeeded.

Lastly, I wish to note that a great discussion in the class was initiated by a demonstration by the professor with a wind-up car. (A toy that, when you pull back and let go, propels itself across the table or floor.) Perhaps the key discrepant event was that when the instructor pulled back the car a distance then moved it back to its starting position (with his hand on it – i.e. not letting it go yet) and let go, the car would start moving. Four students were involved in the discussion, with comments coming quickly after one another and in direct response to comments from other students. In particular, one student replied to another’s comment, “Sorry, but I think you’re wrong.” They then went on to describe their opinion of how the car worked. Having different positions chime in, acknowledging others’ responses and replying to them, and explaining their own ideas; this sounded very much like a real scientific discussion.

P.S. Nobody was enticed by candy to comment on the pre-class overhead. The most common reason cited: too early in the morning.

(Prone bike image: Eva K. (Eva K.) [FAL or CC-BY-SA-2.5 (, via Wikimedia Commons.)



  1. Hi Jared. I would have loved to hear the conversation regarding the pull-back car. I will have to it out next time I teach a first-year Mechanics course.

    Do you feel like your goal is to strictly to bring their prior knowledge into class or to simply give them something interesting that they can use to connect with the course material?

  2. I feel like the goal of bringing prior knowledge into class is especially important in a class such as Physics 100. I think that realizing that they can bring that knowledge in and apply some of their intuition to the problems they see in class would give a big boost to the self-efficacy of students in a course like this. (I think this would be especially helpful for the set of students that maintain that they ‘can’t do physics’.) Bringing prior ‘non-physics knowledge’ into the class is something I don’t think I did well in undergrad. However, perhaps since my ‘physics knowledge’ was fairly sound, I never had a problem with self-efficacy in physics.

    Although I feel the prior knowledge goal is important, right now I’m not quite sure how to achieve it. So, in this semester’s iteration of pre-class overheads, my goal is more along the lines of your second option. My hope is that the experience this semester will spur ideas of how these images (and queuing phrases) can help to break down the usually strict barrier these students have between real life and what they see in the physics classroom.

  3. Simpsons? That shows a bit of a generational gap – do the mid-1990’s babies in your class even have familiarity with the Simpsons? 🙂

    I kid. I really enjoy what you’re doing with this blog though, and post-ISW, I see a lot of value in connecting with the class prior to the lecture. Do you have any plans to perhaps do a survey post-semester to get more quantitative feedback? And is there another section of physics 100 NOT using this pre-class overhead method?

    1. Ha I think Simpsons is timeless! Did you go to the site linked above? Lots of really great science references there.

      I don’t have plans for a survey or anything this semester, but we’re thinking about something for next semester. There is another section of Physics 100 not using these (in fact, I think there are two sections not using these). However, I’m not quite sure what to look for to compare the sections. In addition, I’d expect differences between the sections due to the different instructors and students, which would make it hard to tease out a result there.

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