# Day 118: Building a Model

**Posted:**March 19, 2013

**Filed under:**School Days Leave a comment

I took a lot of pictures today.

We are on day 2 of trying to find a model to describe car crashes. The picture above depicts formulas students developed to represent the relationship between initial and final velocities for two cars that crash together. At this point we have limited the situation based on the conditions below (we brainstormed this list after discussing the formulas above);

The arrow is the limitation we want to tackle next. I showed them a car crash where the cars bounce off each other, via magnets, and said go. Off they went. Below are lots of pictures of stuff they worked on as they tried to figure out the situation. Lots of spinning wheels today, which is good. Tomorrow they get a hint.

In the above picture, the student said, “I’m almost certain this has to be in the top…”

The picture above is a student explaining to her class how she reasoned out the equation first based on the ratios of the masses and how it should work out. That group’s data then supported her theoretically derived equation.

This equation is starting to get to something, though not a universal for all the collisions (I’m being vague since some of my students read this blog!) We’ll have that conversation tomorrow.

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