On a cold, windy yet sunny SF day (the norm), my 7th graders worked out the best possible outcomes for their water balloon bungees. After testing how far a balloon would fall with two, four and six rubber bands, they created a graph and measured the height of the middle school balcony using the concept of similar triangles we had studied months ago. They made a prediction of the number of rubber bands, tied them on, and we all went out to see the results. Two groups got their balloons within a few centimeters of the ground, while other, more conservative groups, did not put quite enough rubber bands out of fear that their data wasn't accurate enough. One group lost their balloon bungee jumper to a concrete finale.
A very fun day and a great way to learn about the power of mathematical modeling.
See photos on my other blog: http://inside.sfschool.org/users/gkenyon/