Fire Away/ Alternative Energy Vehicle
Fire away: Trebuchet
The first part of our third project for STEM was to create a trebuchet with no limitations, except that the longest it could be is one meter in any direction. I was put into a group with Rye Heydari and Chase Vipperman. At first we were only given a few days to build a very basic design that didn't have to travel to far. My group decided to make a trebuchet with a wood arm and stopper, and a clay ball connected to a fishing string as a projectile. For this simple design the furthest our projectile went was 25 meters.
After everyone tested their first design, all the groups had to choose one specific variable to modify various ways and take to find out what would be the best. My group decided to test different types of arm materials as our modification. After testing multiple types of arms, like wood, PVC pipe, and copper, we came to the conclusion that copper was the best arm material to use to get the projectile to travel the furthest distance.
Once everyone completed there modification trials, the class was able to design our last trebuchets with the knowledge of what modifications will help the trebuchet get the furthest distance. For our final design we made six modifications to our trebuchet which are described in the document below. After the changes to our project, our projectile traveled almost 40 meters at one point. Unfortunately, when we started to take data for our calculations a part of our trebuchet broke. Since it was broken the projectile could only travel at most 17 meters.
Alternative Energy Vehicle
For the second part of our third project we had to design a vehicle that uses an alternative energy than gas. The vehicle had to carry two passengers with a total weight of 250 grams five meters then stop exactly at five meters. We stayed in the same groups that we had in the Fire Away project because these two projects were counted as one project. Our original design for an alternative energy vehicle was to create a wind up car, which would use spring potential energy as a power source. After researching, looking at videos, and designing for our vehicle we started to build it. We decided that we would create a frame out of wood where we would put K'nex gears and axles.
Late into building our original vehicle we realized that there were many issues that stopped it from moving. First of all there was way to much friction between the gears, that if we use them we would have to have a spring that provide a lot of power. Second there was also too little friction between the wheels and the axle. This caused the wheels to spin out when we try to move the car. After looking at these issues and more issues we realized that we did not have the correct materials and tools to build this wind up car. Luckily, Chase was able to build a car that runs on gravitational potential energy in about ten minutes. This car ran very well and we were able to get data and calculations for quickly.
Physics
Spring Potential Energy: the energy stored due to a spring's expansion or compression. The equation that is used to solve for the spring potential energy is: PE(potential energy)=0.5 times k(spring constant) times x²(distance moved by spring). We used this equation to find the potential energy created by the 13 rubber bands we used to fire our trebuchet.
Gravitational Potential Energy: the energy an object has due to its position at a height or in a gravitational field. The equation used to find gravitational potential energy is: PE(potential energy)=m(mass) times a(acceleration due to gravity) times h(height). We used in equation to find the potential energy created by our vehicle at a height of 0.28 meters.
Kinetic Energy: the energy due to motion. The equation used to solve for kinetic energy is: KE(kinetic energy)=0.5 times m(mass) times v²(velocity). We used this equation for both our trebuchet and our alternative energy vehicle calculations. For our trebuchet we found the kinetic energy created by the projectile, while for our vehicle we found the kinetic energy created by our vehicle from going down the ramp.
Thermal Energy: the energy lost to heat, usually friction. The equation used to find thermal energy is: TE(thermal energy)=Total Energy - PE(potential energy) - KE(kinetic energy). We used this equation to find the amount of energy that converted to thermal energy when the car went five meters. Since the car had stopped at five meters all the energy converted into friction.
Total Energy: the total amount of energy a body can have. The equation we used in this case to find total energy is: Total Energy= PE(potential energy) + KE(kinetic energy) + TE(thermal energy). We used this equation to find the total energy created by our vehicle. In this situation, our total energy is equal to gravitational potential energy, since the potential energy is our car's source of power.
Rotational Inertia: the resistance of an object to changes in its rotational motion. For our wheels we used CDs because they have more mass towards their centers, which makes it easier to start rolling faster and easier to stop rolling.
Graphs
This velocity vs. time graph of the alternative energy vehicle shows that the car was moving at its fastest at around 0.7 seconds after it rolled down the ramp. Then once the car hit its peak the velocity started to gradually decrease to 0 due to friction.
This distance vs. time graph for the alternative energy vehicle shows that the car traveled five meters then stopped after six seconds. In the first three seconds the car maintained close to a constant velocity.
Reflection
Even though in the end my group completed the project there were a few things that we could improve. Throughout the project our group was behind everyone else because we did not manage our time well. For example, for the alternative energy vehicle project our whole group spent too much time on researching ideas for our vehicle. By the time we started designing our car, other groups had already finished their designs and started to build their vehicle. If we had stayed more focused and managed our time more effectively then we wouldn't have started the project already behind other groups. We also could have divided up the work to save time instead of having everyone work on one part of the car at a time. Another area in which my group could in improve on was our communication. Throughout the project my group was working well together, but we did not communicate enough. For example, there were some times where we said we would meet up at lunch to try to catch up to other groups and get extra work in, but people would not show up. We also didn't talk to each other enough about dividing up the work for the project so we could be more effective. If we had communicated more than the project would have been easier to complete and it would have resulted in a better overall project.
There were also some things that my group did well, besides from our time management and communication. My group was faced with many challenges throughout the project ranging from group members being sick to pieces of our project breaking while using them. I believe that as a team we collaborated well and were able to overcome these obstacles that tried to stand in our way. As a group we also did a good job at being very thorough throughout the project to make sure that everything we worked on was precise. In the end our collaboration skills and our thoroughness are what got us to finish the project on time.