With modeling instruction, we begin each unit with a “Paradigm Lab” — a simple experiment used to build and develop the current physics model we will use to explain how our world works….or some of our world.
The Constant Velocity Model is the first unit (Science Reasoning is Unit 0), and is what a traditional physics class would call kinematics (well, part of kinematics). My set up and delivery is almost exactly like Kelly O’Shea’s.
First hour went quite smooth, although every group started from the origin and went in the positive direction. I knew this wouldn’t make for a lively discussion, so during the five minute passing period, I whipped up some little slips to give to each group.
What I hadn’t anticipated was the discussion these little slips would generate within the group before the whole class discussion. If we start negative, do we stay negative? And what does that mean about our velocity? Will we have a negative slope? And sometimes they realized their negative slope was in the wrong quadrant and they had graphed with negative time, and then admonished one another, “you can’t have a negative time!”
Those who crossed the origin had different questions; what in the world is the graph going to look like? Can we have a negative distance? Oh wait, its not distance….it’s position….so, will our graph cross one of the axes? Hmmm….
In the end the questions that came up (and were sometimes worked out) in their small groups came up again in the large group board meeting. And here we go, putting our heads together to figure out what all this meant and how so many different looking graphs can still explain the same type of motion. Score!
To wrap it up, we discussed the four models (representations) we got from this lab: diagrammatic (which we said was the sketch of our set-up), linguistic (our consensus definition of constant velocity), graphical (a nice linear position-time graph), and mathematical (xf = xi + vt).
A few notes about some favorite things I saw in my students during this lab:
- My favorite “breadcrumb” was the brushes (the artist in the group)
- One group (I later found out) laid several metersticks end-to-end and took video of their buggy. Then, to get accurate positions, they were able to pause the video as needed for their time intervals. Genius!
Do you have some thoughts about this activity? How do you teach your students about constant velocity?