131 It’s RC circuits and capacitor discharge time in AP Physics! (Post originally meant for April 4th)



130 A conceptual student analyzed a video of Super Mario jumping. I think she mis-estimated Mario’s height, which is what she used for a scale in LoggerPro, but apparently Super Mario’s world does have fairly reasonable gravity. Cool!

Video Physics

129 Conceptual students are doing a video analysis project, and this is the first one to try using Vernier’s Video Physics on her iPhone. She is pretty pleased that she figured it out! And so am I!

Circuit Fun

128 I had promised the AP class “Circuit Fun” on the last day before spring break. To me, this means making different circuits to light up light bulbs in various configurations!

Loop Rule

127 (Tuesday, March 26th) I love this question in Chapter 27 of Halliday, Resnick, and Walker. We spent a while in class talking about which conservation of energy loop or loops you should choose to write loop equations for in order to determine the current through resistor R. There is one loop where you can solve for the unknown with one equation. If you don’t choose that loop, you will have multiple unknowns and will need multiple loops and multiple equations to answer the question. (All batteries are ideal and have emf = 4 V and all resistors are identical and have resistance = 4 Ω.)


126 (Monday, March 25th) This video demonstrates the difficulty some groups had in collecting data from the squishy circuits lab. The conductive dough they made never gave consistent readings. When we got frustrated with trying to measure ΔV and I for their dough, we tried measuring R directly using the digital multimeters. The video shows the readings for a given chunk of dough measured in MΩ, fluctuating between 1.02 MΩ in the first frame and 0.55 MΩ in the last frame. There will be a lot of experimental uncertainty to write about in the lab report!


125 The AP class is investigating the resistivity of conductive dough. I was going to make it myself, but then I had jury duty and I had to ask the kids to make it and bring it in. Which they did! It seemed to work pretty well for some groups, but not for others. I will be experimenting on my own at home to troubleshoot some of the issues. Mostly, it had nothing to do with kids using the digital multimeters incorrectly to measure current, though if they did things wrong yesterday they may have blown a fuse and I could not tell. So that is another thing I need to check.

Sticky Tape

124 The conceptual classes are now starting to study static electricity using sticky tape! I love this activity!


IMG_20130319_205852123 I’m on a jury, for the first time ever. So I’m out of school. Garrgh.

Poster Project

IMG_20130315_142007121 My conceptual classes had to make a poster explaining how to solve projectile problems. The idea was that in the process of creating the posters, they would cement the ideas more firmly in their own minds. We shall see, as they do assessments over the next couple of weeks. I do plan on leaving the posters up while they do in-class assessments.