Backyard Physics

Last spring I had an idea: why not dig out the old zip line equipment and put it up this summer, so that we could use it in the fall when we begin a physical science unit with our co-op. Seemed like a great plan, but I didn't realize what I was getting myself into.

I should have known, since I'd put up the zip line once before--thirteen summers ago. Our property is covered with mature trees and slopes down to a creek, so it seemed mandatory that we install a zip line. I researched it, bought the equipment, found two trees that seemed like good candidates, and went to work. Many sweat-filled days later, we had a zip line. My sister and her family came to visit just then, and before we'd had a chance to test it out, my hyper nephew jumped on it and zipped down the hill. Unfortunately for him, it went WAY too fast, dragged him on the ground at one point, and came to a very abrupt stop. He wasn't injured luckily, but we decided that location simply wouldn't do, so we took it down.

Over the years from time to time I'd look for a different location for it, take out the equipment, lay it out between the trees, think about putting it back up, then change my mind and put it away again. But this summer I decided the zip line had to go back up. We've adopted three kids and had another one of ours since the first time it was put up, so it was all new to them.

The job came with a long period of trials and testing, and here's where the learning came into play. Friction, tension, torque, center of gravity, material strength and properties, biology (how to not kill the trees)--all had to be considered. I did a lot of talking and showing to the kids as I went along, but honestly I was learning right alongside them. We watched some YouTube videos. We did some math. I put up the zip line and took it down several times, between several different trees (everywhere I wanted to put it, the ground sloped up in the middle and down on the ends--finally found a spot that works). There were the battles with ticks and briars, rocks and branches. I was attacked by a nest of yellow jackets when chopping down a small tree right over their underground nest (that's entomology). I put my face through quite a few spider webs when walking in the woods (that one too). I sweated like a pig (or whatever animal sweats a lot).

But in the end it was worth it! We now have a great new toy, and I've got a teaching tool for our co-op this fall. No pain, no gain.