## Tuesday, November 27, 2012

### Word of the Week: Centroids

Each week I have my students for a Math Lab. This was supposed to be an extra enrichment or intervention period, but it's turned into organized chaos. I have 20-30 students in 3 different courses all vying for help and attention. It's that class that I dread leaving for a sub....chaos.

My Geometry students are at the top of the food chain and it breaks my heart to give these critical thinkers "drill" practice when they could be exploring. Today was one of those days when you're not sure if an activity it will bomb or fly. And this one? It flew!

We have been studying centers of triangles (orthocenters, incenters, centroids, and circumcenter). This has had 2 highlights for the kids: a foldable that they used to keep them all straight and giggles when one student kept slipping and saying "circumcision" during an oral presentation. They are always cooperative and brilliant, but I wanted to give them some reference into why this stuff might matter. Good thing I spent 3 semesters of college teaching physics! Centroids.....centers of gravity....suspending random objects around the classroom? Sounds like it's worth a try.

I used this video on center of gravity to introduce the topic. One their interest was piqued, this video related the information to our chapter. I had each student design a triangle out of cardboard and find its centroid, then suspend it. Then they had to find some weird shape other than a triangle and try to find its center of gravity. Can you find a centroid for that? How is it alike and different? All questions to be examined!

Anytime you get to hear "whoa!" and "that's so cool" is a good day in my book. I had to shoo students out of the room when the bell rang and we spent the first minute of class later that day balancing our triangles on smaller and smaller points around the room. One student got it balance on the head of a pin....he took it home because he just HAD to show his parents. Here's a great activity that I wish I had thought of before today....could have been integrated nicely.

The only problem? The 20 Algebra students I had in the class found it nearly impossible to focus on their linear equations project with all excitement! They wanted to build their own centroids and were even starting to use the vocabulary. I love when, at the end of class, I catch students who aren't even in the course watching videos I've posted for other classes (also a problem with Vi Hart's videos!). As I was walking out to my car I found 3 triangles, centroids labelled, that had been made by students outside my class. Love when math leaves the 4 walls of my room!

Any other ideas for integrating more physics into high school math? Obviously with calculus, but with lower level? Share share share!