For the Hybrid Car project, each group was required to design and make a prototype of a car that would store potential energy (stored energy) and convert it into kinetic energy (energy with motion). We could use anything to make our car go, except anything remote controlled, nuclear, or chemical. The cars had to carry 250 grams of weight 5 meters. The vehicles also had to stop as close to 5 meters as they could. My group started out with the idea to use a wind-up car method. We would wind up the car's back wheels with a rubber band, and when we let it go, it would speed to 5 meters. This ended up being much more of a challenge to complete. We soon realized, that the rubber bands wouldn't have nearly enough potential energy to carry it 5 meters. With this setback, we had no idea to do instead, we knew that rubber bands could store a lot of energy, but not in the way we were going to use them. Mr. Williams helped my group and pointed out that there were a lot of rat traps in the room not to catch mice, but for the purpose of the Hybrid Car project. With this new idea for our car, we eagerly got out a mouse trap. We would still use rubber band to store the potential energy, because it has a lot of elastic potential energy (potential energy stored by the compression or expansion of a spring). When the hook was released, the metal rod would snap forward, and pull the rubber band, which was wrapped around the metal rod, which would, in turn, pull the back axle and spin the wheels. This idea would not work either. The rat trap had WAY too much power behind it and, we ran into some sophomores who had done the same project, and they informed us that the rat trap car didn't work with any of the groups that attempted it. My group and I knew that the rubber bands could store a lot of energy, but only if we stretched it. We decided that the rat trap gave our car too much power, but wrapping the rubber band up manually would give it just enough. My group wanted our car to be light, so we chose to use cardboard as our wheels, and body. We spent our second work day making the wheels of our car, and our third day finishing the wheels and putting the car together. On the third day we realized that our cardboard body couldn't hold the screw that would hold the wound up rubber band, because it was too flimsy. We wanted our car to be light, but in order to have it work, we needed to use wood. We found a good piece of wood that was light and sturdy to use as our new body. We also determined that our cardboard wheels weren't working as well as we wanted them to, so we decided to switch the back ones to CDs and keep the front two as cardboard. By this time my group and I had to come in at lunch in order to finish on time. My group and I were behind most of the other groups in our class with the product of our car. While most of the other groups were already on the slideshows of their cars, we were still working on the prototype. The day before our presentations, my group needed to extend the nose of our car. This was because the rubber band needed to be stretched even farther than we could with the current length of our car. We also needed more power to move our car the 5 meters-- the one string of rubber bands didn't give it enough power. To fix this, we made another string of rubber bands hoping this would give the car the power it needed. It did! Our car now had enough power to travel the required distance, but it was having trouble moving in a straight line. This was because our axles weren't held in place, to reduce friction we didn't have something keeping it from turning. To solve this problem, we attached a straw to the body of the car and stuck the front axle through the straw, and the back axle through a PVC pipe. This would keep the wheels in one place and guide the car in a straight path. We were also having a problem with the front cardboard wheels. They were too raggedy and the holes for the axles weren't straight anymore. We scrapped the cardboard wheels and replaced them with CDs also. Our car was finished. At the end of this project, our hybrid car had changed A LOT! It went from being a wind up car, to a rat trap car, to a cardboard car with a rubber band, to a wooden car with 2 rubber bands and cardboard wheels, to a wooden car with 2 rubber bands and CDs for wheels. Despite all of the problems my group and I had with our car, it was a fun project! I liked being challenged to come up with a car on our own, with virtually no restrictions.
My group and I worked well together, I think this was partly because we got to choose our groups for this project. We also all wanted to get a good grade on this project and most of us put in the same amount of work into the car. One of our group members didn't put as much care into our car it seemed. She would take a lot of breaks during the day, but despite this, she came up with a lot of the ideas for our final product. For my next project, I need to keep working on listening to my group mates. One of the members of our group suggested a lot of the ideas we ended up using on the end car, but she had suggested them in the beginning of our project--if we had listened to her, I think we would have finished a lot sooner. I will also make sure I am always doing something beneficial to the project. I did this a lot on the physics of sports videos, but not as much on this project. I think this was because I had a lot of leaders in the hybrid car project, and I took a step back. I think I am good at cooperating and finding something to do if everyone is working on the same thing, but I can still work on it. The hybrid car project was a fun way to really use our imagination and come up with a semi-efficient engine for our small cars.
Here are the concepts and equations we used in the making of our car: Elastic potential energy: energy stored by the compression or expansion of the spring-- PEspring=1/2kx^2 Kinetic energy: energy due to motion--KE=1/2mv^2 Spring constant (k): measure of how easily a spring is compressed and expanded--K=F/d Thermal energy: energy due to heat-- Total energy: the sum of kinetic and potential energy--TE=PE+KE