Day 31: Van de Graaff Generator & Newton’s 3rd Law

Physical Science: Van de Graaff Generator

After sharing and discussing observations from yesterday’s lab, we played with the Van de Graaff generator. I like to end with sending a shock through a chain of students, then have two students hold onto an aluminum rod instead of holding hands. Students aren’t too surprised when they still get shocked with the rod in the chain. Next, I switch out the rod for a wooden meter stick and students aren’t too surprised when the shock stops at the meter stick, which provides a nice segue into conductors and insulators. This year, I also had students hold one of the rubber rods they’d used in their static electricity lab. Since it had been easy to give the rubber rod a static charge, students expected it to work at least as well as the metal rod. I’d tried this on a whim, and it ended up being a great reminder for me that students don’t easily differentiate between carrying a current and holding a static charge.

Physics: Newton’s 3rd Law

Students made free body diagrams for a variety of scenarios with two carts colliding, then predicted which cart would experience the greater force. After students had worked, we used a pair of force sensors to test their predictions. I’d also planned to show Frank Noschese’s great video of cart collisions, but ran out of time, so I’ll start with that on Monday. There were some great debates when students were working on their predictions, though students were more insistent than usual that I should step in and tell them who was right. This provided a good opportunity to talk with my classes about what we know is needed to really internalize a new concept, which helped alleviate some of the frustration with my non-answers.

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