Bowling Ball Debrief #1-5 only on Whiteboards
–> 2 students still thought that an object in space would eventually slow down (“loses energy over time” , “loses force”) while other students rightly said that w/o friction it would keep moving.
So we played with the hoverpucks to TEST a hypothesis:
* If it was “losing force,” then it would slow down even in a frictionless environment.
Kids saw constant speed. I talked about how friction was like tiny mallet taps when the bumps in the floor and ball hit each other.
Introduced Unit Notes sheet — a way to keep track of key concepts, ideas, equations, etc. from each activity.
Discussion Notes for Activity #1 Bowling ball & Mallet — speed up (tap same direction), slow down (tap opposite direction), steady speed (no taps -or- tap same-opposite), friction vs. no friction
Finished up the period by riding the large hovercraft!
We spent these 2 days (3 periods) on a lab performance assessment. It was split into 2 parts: an individual portion and a group portion.
The individual portion had 3 tasks:
(1) Find the speed of a green buggy using a stop watch and meter stick;
(2) Find the speed of a green buggy using a motion detector and Lab Quest 2;
(3) Find the speed of a green buggy using video analysis in Logger Pro.
I had 4 stations set up for each of the 3 tasks. Students spent about 20 minutes at each station and rotated through. (The video for the video analysis task was pre-made by me.)
The group portion had 1 task: Design an experiment using a pull-back truck to find a mathematical model relating 2 variables. Students worked in groups of 3 and had 60 minutes to complete this task. They could graph their data by hand or use Desmos.
Half the class spent the first 60 minutes of the 3 periods rotating through the 3 individual tasks while the other half worked on the group task. Then they switched for the remaining 60 minutes.
As a unit review, and as a way to create some “formal notes” for students who have been asking for them, we did some collaborative whiteboarding, speed dating style. Each group was responsible for whiteboarding one of the following quadrants on this sheet:
The catch? They only had 2 minutes. At the end of the two minutes, the groups rotated to a different board. They then had another 2 minutes to add (and/or correct) information on the next board. As we rotated through, the boards slowly filled up. (If I had thought ahead, I would have assigned each group a different color marker, so it would be easy to track which groups made which edits on each board.)
Once every group has gotten to all the other boards and is now back to their starting board. Each group then presented their completed board to the class.
Today was a quiz day, and I forgot to take a picture of something interesting. But today I received a request on Twitter for all my voting slides for Preconceptions in Mechanics.
I shared these presentations last year, but they were part of individual posts and I hadn’t put them all in a single folder to share. And now is the time that folks are starting to teach Newton’s Laws. So, thanks to that tweet from Kim Freudenberg, I put all the slide decks into a single folder along with the Preconceptions in Mechanics book: https://drive.google.com/folderview?id=0B4h2KfPMJ6ONNko5Sm9iVjZiWXM&usp=sharing Enjoy!
YESTERDAY: The intro lesson on electric potential difference was a flop. I had students solve problems about moving particles in constant electric field for varying amounts of charge:
Then I asked them to generalize for any amount of charge q:
and then tried to make the connection to this new quantity called electric potential difference. Big flop. It felt abstract and contrived.
AFTER CLASS: I dug into Knight’s books and Etkina’s book to see how they approached it. Both of them did potential first (not potential difference), and took a fields approach to potential. They drew parallels between the relationship between electric force/electric field and electric potential energy/electric potential. This seemed like the most natural approach for our class, since we’ve been rocking electric fields for weeks and just finished up electric potential energy.
TODAY IN CLASS: We talked about Knight’s conceptualization:
and Etkina’s (she goes a step further and literally calls electric potential the V-field):
And if electric potential can really be treated like a field, we need a way to visualize it. But it’s not a vector, so we can’t visualize it like we do electric fields. I talked about the concept of a scalar field (or “heat map”) and showed this map of air pressure in Europe:
We discussed what the colors meant and what the lines meant. (They all had Earth Science previously, so this wasn’t entirely new to them.) Then we looked at the PhET’s Charges and Fields simulation:
I think visualizing the V-field was really key, rather than taking the “work-based” approach I had done yesterday. The picture at the beginning of this post is a summary sheet of the discussion.