Math In Action - California Highway Patrol

This episode features the California Highway Patrol Multi-Disciplinary Accident Investigation Team performing analysis on a set of tire tread marks to determine the speed of the vehicle that left the marks. Students will measure, substitute variables into a velocity equation involving a square root and simplify, and perform unit analysis to determine the speed of the vehicle in miles per hour (Youtube video here...links to download below).

Lesson Suggestion

Get the kids involved. Have them guesstimate or measure SOMETHING. That's something we don't do enough in math classes, but that's for another blog post. I started the video at around 2:56 and played the speeding car. I asked them how fast they thought the car was going on received a range of responses from 50 mph to 100 mph. I recorded responses from each pair of math buddies (that's what I call groups in my class) so that I could ask questions later once we found out the real answer.

Then, I upped the ante a bit and asked them if they could show me how long it would take (in feet) for a car to stop that was traveling 50 mph. We went outside and I had them stand at the mark that represented the length that their math buddy cohort came up with. We had everything from 10 feet (really?) to around 30 feet from the railings pictured. It looked something like this (sorry for the crappy Photoshop skills, but I need to protect the identities of the innocent somehow:

The students were shocked to find out (after some calculations and watching the math portion of the video) that the answer really looked something like this (notice the faceless student about 75 feet away from everyone else...BTW, the kids had their pick of how to go faceless and they were split 50/50 between a clone of me and having their souls sucked out of their picture by me erasing their face. It's on them.):

The substitutions and simplifying ended up being the easiest part for most students, while the unit analysis and guesstimations on the distances seemed to be the hardest. After watching the interview portion of the segment we talked about the guesses and things like mean, median and standard deviation without actually calling it those things until the end of our discussion.

Links

The download link below is a link to a high quality Quicktime file. You can also use Keepvid to rip it straight from Youtube, or Video Download Helper if you're a Firefox user.

Direct Youtube Link: http://www.youtube.com/watch?v=z4x2mdtqaz0

Download Link: http://www.mediafire.com/?umnthzyknwb