What We Did
For this project we were asked to build a car with an alternative energy source that could travel an exact five meters with 250 grams of weight on it. After my team and I debated for a while on what to do, we decided to do something a little risky. We decided we were going to try to make a coke and mentos/waterwheel powered car. The idea was that the coke and mentos reaction would apply enough force on the water wheel that the water wheel would start turning and push against the ground, causing the car to move forward. However after building our car and setting everything up, it turned out that we had the coke and mentos reaction spraying at the wrong angle. Once we figured out our problem, we reset it up and positioned it in a different angle, but sadly this time there was to much force on the wheel and not enough on the ground. Thus we decided to test it one more time for hopes sake, and this time there wasn't nearly enough force, and the wheel wouldn't move at all! So with one and a half more days to build our car, we decided to go a whole different way and build a rubber band car. We decided to keep the same wheels and body since they worked very well and we knew we had to finish and perfect it in a short amount of time. However, we did end up modifying the back wheels. Since we were transforming our car into a rubber band car, we had to have a place for the rubber band to be able to attach to and wind up on. We first unscrewed our back wheels, and sawed our pipe in half where the axle of the wheel went through. After screwing back on the pipe to the body of the car, there was about a half in space between the two pipes. This is where we screwed the screw into our axle, and would be where the rubber band hooked onto. To finish off, we attached zip ties to all four sides of the wheel adjacent to the pipe. We did this so the wheels wouldn't move side to side while in motion, and cause friction between the rubber band and pipe. Furthermore, we added a long pole to the front of the car so we would be able to twist up the rubber band more times, allowing the car to travel farther. After doing these quick changes, and lots of testing and tweaking, we were able to successfully move the Hippie Mobile five meters!
Content:
- Spring Constant : the rigidity of the spring which can be found by force divided by distance. We found the spring constant by using a spring scale to measure the force of the rubber band divided by how far we pulled it.
- PEspring : the spring potential energy or the energy stored in a spring by pulling or pushing it. You can find it by multiplying the spring constant times the distance moved by the spring squared times one half. We found this by using the spring constant we found and the velocities we've calculated and plugged them into the equation.
- Kinetic Energy : energy due to motion found by the equation KE=1/2 x mass x velocity^2. We found the Hippie's mobile kinetic energy by plugging in the weight of the car with the masses on it, and plugging in its velocity at each meter.
- Thermal Energy : energy lost to friction. My team and I found the thermal energy at each meter by taking our total energy and subtracting our potential and kinetic energy at each meter.
Reflection
I think over all, everything went very well and our team worked great together. We tried something risky, and when it didn't work out we didn't give up. Instead of getting fazed, my team and I started right away on our new hippie car. I think during this project I really stayed on track and contributed lots of ideas. When we started on our new car, everyone stayed positive, and I think it is what really helped my team to not give up and keep pushing forward. I think I can still work on taking more leadership roles. During this project I took more than I have been in the last ones, but I know I can be even more of a leader by really keeping my group on track and focused. Furthermore I think I can improve on staying on track as well. I'm not that off track, but I did get a little side tracked looking at others peoples cars that were really cool instead of focusing on mine. However I think overall, this project was great and my team did very well.