Thursday and Friday were both so frantic that I’ve lumped them into a single post. It’s a bit lengthy, but I think it captures the spirit of the Zariki 2012 Summer Institute of Technology and Engineering.
Thursday started off early. Chelsey and I had been working on Thursday’s lesson plan for the past week and we still weren’t quite sure what to expect. The class was a staple of the ELiTE curriculum, but over the past few years we still hadn’t quite managed to condense the class into a succinct and comprehensive unit. The class introduces simple machines (ramps, levers, screws, wedges, pulleys and wheels) as the foundations of mechanics, and I had no experience teaching the topic. I woke up at 5AM to discuss the lesson plan with Chelsey and worked frantically through the morning to arrange my class.
When I arrived at the school I came up with my first real lead on the lesson. While scouring the campus for materials to use for the inclined plane and lever experiments, I discovered a welded iron ladder that had been used to install the solar panels. I set up a fence post as a fulcrum on top of a raised mound of dirt, and produced a rather elegant see-saw. The students had not yet arrived so I wasn’t worried about making a bad impression. Thus, I decided to see what I could do with the contraption. Matt and I found a large rock and set it up on one end of the ladder, while I jumped on the other end to launch the rock into the air. There was a bit of a rise, but we decided to slide the ladder down a bit to get better leverage for our DIY catapult. Matt came in this time to launch the stone, and promptly fell on his behind as the rock sailed 5 feet up into the air. Luckily no one was hurt (we have proof on video!), and I can safely say that the activity gave Matt a solid ‘grounding’ in mechanics.
(picture & viral youtube clip on Holly’s camera!!!)
The ladder was removed after this fiasco, but I found another fencepost to take its place for the lesson. Once the students arrived we discussed the principles of force, energy and power before launching into our activity. The students measured the force required to pull a fifty-pound stone up the ramp at different angles, and compared it to the force required to pull it straight up through the air. After some calculations, we found the force of friction on the rock and confirmed the result with another experiment. We followed this with a smaller demonstration using a small weight and a tilted desk. After the inclined plane experiment, we set up the contraption as a lever and measured the force required to lift the rock with the lever resting at different positions on the fencepost fulcrum. We worked through some preliminary calculations before breaking for a late lunch.
The afternoon session didn’t run quite as smoothly. I strung up a couple pulleys from the rafters and looped a rope through the assembly to test the system’s mechanical advantage. I asked one student to hang on to an end of the rope while another tried pulling him up. We quickly discovered that one pulley had little effect on the apparent weight of the student hanging off of the rope. I looped the rope through a second pulley and we suddenly had very little trouble lifting the student’s weight. However, when I tried attaching more pulleys the friction from the rope jammed the system and we weren’t able to get any more mechanical advantage. I was flustered by this set-back and I think I bored the class to death while I tried to find a solution. Eventually I moved on to the activity for the wheel and axel and we had a great time. I gave students a collection of gears, Styrofoam boards to use as platforms, and pointed them towards the Wiba needles in the Acacia tree in the yard (think cactus spikes) to use as axels. The students played around with the equipment to set up gear trains that could distribute power and rotational speed differently based on the ratio between the gear sizes. We then connected battery-powered motors to the contraptions, and eventually motors powered by my small solar panels, to create powered drive trains. The students had a blast making little machines from the equipment and learned a great amount about the transmission of force through gear systems.
The delay from the gear activity ate up our time for an afternoon competition, so after class I jumped in the car to go back to the hotel. We had to relocate for a night, and so we drove a few miles away to the Ndabaka hotel in Lamadi. The hotel had wifi (hooray!!) so I finished some blog entries and checked my email. We had a delicious buffet dinner, and after some more time at the computer I went to bed.
I slept wonderfully. We had a late start in the morning because of breakfast and transportation delays, but I had already planned a shorter lesson anyways. We started the class by revisting the gear systems the students put together on Thursday. I asked the students to attach motors to their machines without batteries, so that they could measure the current and potential generated by the motors with the multimeters. The students watched as the multimeter registered different amounts of power depending on which gears the students turned. The activity wasn’t exactly precise, but I think the class started to grasp the basic function of a dynamo. After playing for a bit we took a quick Math break to solve the quadratic equation (a request from the students!). Then I introduced the practical application of the motor dynamo for electricity generation.
I set a pile of popsicle sticks, glue, string, cardboard and other materials at the front of the class and asked the students to try their hand at electricity generation. Most groups worked on simple mechanical generators, but a few put together model windmills and water wheels! All of the groups managed to crank out some usable electricity to power a small LED, and a few of the projects really started to look like the real thing! I was incredibly impressed with the students grasp of the concept and resourcefulness with their projects. This class really highlighted ELiTE’s mission and goals, and made me feel all warm and fuzzy inside. As a finale to the SITE classes I’d say it was a huge success.
During the generator class I took aside a few students for interviews with Tony. The language barrier was challenging, but we got some good feedback from our students. I also spoke with the Zariki teachers to set up plans for post-session ELiTE activities. The afternoon was busy but productive. I even managed to squeeze a few minutes for lunch into the day! By two PM we started the final engineering challenge: the water balloon drop. This challenge was based on the common elementary school Egg Drop. I gave each group a full water balloon and told them to use available materials to protect their balloon from bursting after a fall from a particular height. They only had 50 minutes to build, but the students were experts at this point in the engineering contests. Some groups used straw to cushion their balloons while others combined Styrofoam with cardboard for a more rigid structure. These products were the most creative I had seen so far and I was really excited for the final contest. At the end of the timer I stood up on a table and gathered the students around for the drop.
The contest was arranged as a single-elimination sequence of levels, from a low drop all the way to a toss into the air. All of the balloons made it through the first couple levels. The tension really started to peak once I started reaching high into the air to drop the balloons from a significant height. With Tony’s camera rolling, we anxiously watched as three of the six balloons burst. We entered the next round with shouts and applause as I started tossing the balloon containers into the air. One after another, each contraption burst the balloon until the very last entry. Every set of eyes was fixated on the balloon as I launched it into the air, and miraculously the package was picked up off the ground without leaking a single drop of water. The crowd roared with applause as I lifted the winning entry into the air, until a thin trickle of water dripped out of the container and the we all burst into laughter. The competition was a fantastic spectacle, and I’m thrilled that Tony captured it all on video! After we cleaned up and said goodbyes I improvised a cheesy speech for the students. It was such a short program that it was a shock to say goodbye, but I look forward to the Tanzania SITE in the future. With teachers and students shouting out goodbyes we hopped into our Safari Trucks and headed off for the Serengeti!