For this project we were assigned a very challenging task: we had to build a car that traveled five meters without using batteries, gas, or any other kinds of chemical energy. Brandon, Zoe, Eli and I put our heads together to create a solution to this difficult problem.
Our first model seemed promising at first but turned about to be a complete failure. We based it off the idea that balsa wood planes can spin the propeller dozens of times after only being wound up once. Unfortunately, the rubber band had such a ridiculously low spring constant that we couldn't get it to start moving, even without the weights on it. This was our first model:
Our first model seemed promising at first but turned about to be a complete failure. We based it off the idea that balsa wood planes can spin the propeller dozens of times after only being wound up once. Unfortunately, the rubber band had such a ridiculously low spring constant that we couldn't get it to start moving, even without the weights on it. This was our first model:
After the initial failure We looked at what had caused the problems. We determined that It wasn't sturdy enough, it needed two axles, (not just one), and it needed more power. We made these changes by getting more rubber bands, bottlecap hubcaps, and adding the needed axle. Once we had made these changes our car worked like a charm.
Concepts
Spring Constant - The spring constant is a measure of the elasticity of a material. How far a spring or other elastic material extends or compresses is proportional to how much force is applied in each direction. That proportion is called the spring constant. We used it in our vehicle to figure out how much we should wind up the band to get the most accurate distance. The unit are Newtons per Meter (N/m).
Pressure - This is the amount of force exerted on a given area. When we were brainstorming, many of our designs involved pressure, even though the end result didn't. Measured in Newtons per square meter, or, the Pascal (Pa).
Power - The rate of which work is exerted. Our car had a decent amount of power; this amount could be doubled, however, if you used the second rubber band. Power is measured in watts (w).
Elastic Energy - Energy stored in the stretch or compression of an elastic substance. We found this out at each meter our car went by measuring how many times the band was still wound around the front axle. Measured the same way as all other energy sources (J).
Reflection
We initially had high expectations for our car. When Mr. Williams first gave us the introduction for the project, we (the team) had very high expectations for it. We thought that the balsa wood plane idea had a great chance of success. We were wrong. One of our Pits was having too much confidence in our original design, and not making a backup plan. This leads into our second Pit. We didn't work as efficiently as we should have, and this forced us to spend time out of school.
Our final result was our highest peak. We did not spend much time on our second vehicle, the Osiris. However, it was definitely a very strong contestant. It ran very quickly and could even make it to seven meters if we wanted. Another Peak was how diligently we worked when we really needed to. This all led to having a great car and a great project experience.