Monday, May 6, 2013

Classical Mechanics and Hot Wheels

My family went to the Children's Museum of Indianapolis last week to see the Super Heroes exhibit before it closed May 5. While there, I was also able to see the Gecko exhibit and of course, we stopped by the DinoSphere. We ended the day at the Hot Wheels exhibit, where there were numerous cars and ramps available. It reminded me of many happy days in my grandmother's basement, setting up orange plastic tracks and running cars down ramps, through loops, and into little green army men.

This particular portion had four ramps in a row, each with slightly different features, the closest one with a fantastic gap to be cleared (and an optional plastic shark to jump over or ram into).

As I was playing with my boys, we noticed that some cars made the jump consistently and others did not. Why would that be, I asked myself. Because some are heavier and will fall faster, I answered, and then very nearly walked on to the next exhibit.

Turns out, there's one little problem with this...

Once in the air, the cars will always fall at the same rate, no matter their weight. It's the faster cars, not the heavier ones, who will make the jump. My brain defaulted to the intuitive and wrong explanation of physics. I had to wonder, how many kids came to the wrong conclusion, and how many parents even explained it incorrectly to their kids, as I almost did? What was it that made me stop and recognize that I had fallen into the same misconception of gravity that I had as a child in my grandmother's basement?

It strikes me that this context—Hot Wheels cars racing down ramps—would be a great opportunity for a physics education intervention. Imagine, for example, a space where one would drop a heavy and light car at the same time and see which hits the ground first, and then tandem ramps where the same two could be raced.

I don't know if that would be an effective museum-based intervention for teaching physics or not, but it made me reflect on the misconceptions that people harbor toward computing. Whereas physics has almost thirty years of research on the Force Concept Inventory, we have nothing so well established in computer science. If we don't know what misconceptions people carry, it's hard to imagine designing interventions to overcome them!


  1. Some papers on programmer misconceptions:, a master's thesis.'s_So_Hard_About_Learning_to_Program%3F (contains references to more other papers on misconceptions).

    The interesting thing is that misconceptions appear to be resilient. That is, when students are shown that their mental model is incorrect, the incorrect mental model persists despite the student's being presented with evidence that it is incorrect.

    1. I am familiar with the 2010 SIGCSE paper, though not the others. None of them, however, have had the momentum or replication that the FCI has in physics education.

      In 222, I like to talk to my students about the impossibility of unlearning, to address why it's easy to read a book like Clean Code but hard to implement it. I didn't expect the phenomenon to hit me so suddenly at the Children's Museum, though!

    2. The SIGCSE '10 paper by Guizdial and his Ph.D. student didn't actually include the questions they were trying to use to replicate the FCI. Perhaps we could follow up with them to see if they have validated their results and would be willing to share. We might be able to help with the replication question.

  2. Note that Tew & Guizdial had a followup in SIGCSE '11: "The FCS1: A Language Independent Assessment of CS1 Knowledge."

  3. Darn! One of these papers I just pointed out says that students who passively watch demonstrations of code get nothing more out of it than those who didn't see any demonstration. It appears students need to be engaged and answer questions like "what do you think will happen?" This is going to be a challenge for my on-line teaching - I'm going to need to remember to pause and ask questions during the videos I'm producing of the demos.

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