## Thursday, October 4, 2018

### The Universe Tells You If You're Right

Three recent, easy examples of ways that I've let the students know that they're not trying to please me - that I'm not the final arbiter and source of everything physics-y - came this week in the form of lab practica in three different courses:

AP Physics C (Mechanics): The Bouncy Spring
The students program a Glowscript animation of a ball on a spring, initially released from a position diagonally below the pivot point of the spring. Crazy bouncy motion ensues, but... did we do that right? Pair some high-speed video with the animation and see! For fast finishers: relate the loop computation rate to the frame rate of the camera and get the video and animation to move in sync.

Honors Physics: Ramp Rolling
Sitting in announcements last week, I thought about a ball rolling down the long, gentle slope in our auditorium, then hitting the wall after rolling across the flat ground. Hmm... how far up the ramp can I take the ball before it hits that wall? Easy enough: split the kids into three teams: a team to determine how the ball moves on the ramp (they figure out the translation: what's its acceleration on the ramp?), a second team figures out how it moves on the floor (acceleration again), and a third team does a derivation to put it all together, taking assumed results from teams 1 and 2 and deriving a function for the ramp distance. Works pretty well, and the gentle curved transition gives us an opportunity to talk about error analysis.

Electronics: Resistor Circuits
Were your Kirchoff's Laws and Ohm's Law calculations right when you analyzed that three-resistor circuit? Yes? No? Measure it! Really simple here - gives practice breadboarding and measuring that the kids wouldn't get from just a thumbs up/down from me.