Home » Season 2 » III Form Physics: First Engineering Design Challenge

# III Form Physics: First Engineering Design Challenge

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By Lindsey Dumond, III Form

III Form Physics: First Engineering Design Challenge

Units 1, 2, and 3 all focused on the same design challenge, which was to create an object with the highest average velocity over two meters. The object also had to be self-propelled and could not leave contact with the track at any time, or it would be disqualified. At the end of unit one, we chose several materials that we thought would be most useful in creating an object that could complete the challenge. We created a first design based on what we knew about physics at that point. In unit two, we built a model of our first design and tried to make it self-propelled. After facing challenges during this step we redesigned and rebuilt. As we redesigned, we were also learning more about physics and concepts that we could apply to our design and model to make it perform best. This process continued throughout the rest of unit two and unit three until we reached a design and model that worked and could complete the challenge.

We created our first design at the end of unit one, when we had already covered topics like acceleration and velocity. During our first design, we didn’t think much about the physics aspect other than that our object shouldn’t have a huge mass because it needed to propel itself, and that we needed to make it fairly aerodynamic. We knew that the larger the mass of the object, the more force would be needed to make it move, because of f=ma. We created an object with two axels made of straws that were connected by plastic balls and Popsicle sticks, with a wheel on each end of each axel (total of four wheels). When we were creating this first design we put off the idea of self-propulsion, so after we built the model of that design in unit two, we were stumped. Our first idea was to wrap rubber bands around the axels in such a fashion that when we released the rubber bands, they would contract and spin the axels in the process. We spent a good amount of time trying to figure out how this would work best. We tried a variety of different ways to wrap the rubber band and nothing was working. This was because the heavy wooden wheels made the mass of the object far too large and we would have needed a much larger force to move it, and the rubber band did not have enough potential energy in the ways we were wrapping it to propel such a big mass. The rubber band would need more tension and we would have needed to stretch it more to create more potential energy, but we couldn’t do this without bending our flimsy straw axels. Since we couldn’t figure out our way around the rubber band, we decided to try a new form of propulsion.

Going into our second design at the end of unit two, we were thinking of other ways to propel our object without a rubber band. The only other material that we had access to that could provide the amount of elastic potential energy that we needed to move our object was a balloon. We built a contraption made up of a plastic bowl and Popsicle sticks that we could put the balloon in to make it stay straight as it released air. Making the balloon release air straight would keep the object moving straight, which would give the shortest path from start to finish and therefor allow for the highest average velocity. Newton’s Third Law should have caused the object to move forward when the balloon released air because there needs to be an equal force moving in the opposite direction of the air, but the balloon did not have enough potential energy to move a mass that was still fairly large. We still needed our object to move somehow across the track so we essentially just attached it to the back of our existing model from our first design. We made the decision to keep the wheels because at the time we thought the balloon would provide enough additional potential and kinetic energy to move the object. In the end, the mass was still too high for a single balloon to propel, and when we tested this new model, it still did not move at all.