# Day 98: Bumper Buggies Last Day

Thursday, 23 January 2014

This is what happens when kids have just a little too much free time during a lab. I’m not complaining.

The last classes in my rotation finished their bumper buggy lab today. All of them predicted a collision location and time then tested to see how far off they were.

About 80% of my kids used something I characterized as guess and check for predicting the buggy crash: They figured the position of each buggy after 1 second, then 2 seconds, then 3 seconds. Once the kids realized the crash (for most groups) was somewhere between 2 and 3 seconds, they started figuring buggy positions for half second increments. Most groups did a little “eh, this looks about right” interpolation here. Some kept breaking the time intervals down into smaller increments to be precise. Though a few of these groups did say “there’s got to be an easier way”, none of them seemed really interested in testing it.

About 18% wanted to use a graphical solution — recognizing that the buggy crash happens when two linear functions intersect. They needed support transforming the linear functions they plotted using video analysis the day before into the new start location and direction I dictated today. For instance, kids whose buggies traveled in the negative direction didn’t come up with “duh! I need to multiply my original slope by -1” on their own.

Only one group suggested an algebraic solution to find where two functions intersected. But dang, was I proud of that group. They, like the group above with graphical solutions, needed some help formulating the equations of the two lines.

Why do these labs take me so long? The constant velocity buggies lab took 2 days with all of my classes. Due to our rotating schedule, I don’t see kids every day, so it looks like the lab stretched all week.

Here is the highlight reel of collisions:

Note to self: Next year, I’m modifying the Bumper Buggy game to use longer distances between buggies and create situations with radically different buggy speeds. It’s no fun to predict a crash within 2cm of the center of a 2m long course.