Team Wharton A
We sat in a circle discussing our materials (3 Dowel rods, paper bag, tennis ball, trash bag, electrical tape and case, paper clip, 3 rubber band) and available tools (scissors and a ruler) and what we could do with them to be both creative and effective. We debated different possibilities, and everyone suggested any ideas that came to mind, not discounting anything. Travis recorded the ideas as they came up. As we discussed, we eventually came to a general consensus about our plan. We agreed to meet early the following Saturday morning to build.
Here are the possibilities that we discussed:
-Create a flat surface with the greatest possible surface area
-Make it spin
-Cut dowel rods and tennis ball (into pieces)
-Cut ball and stick paper clip in to use as a fish hook
-Cut rods and tape them together to make more than three
-Wings - cut bag on seams at an angle
-Place ball in bag
-Remove drawstring and use it for something else, stretch bag
-Impale ball and stick rods in
Choosing the Final Design and the Construction Process
First of all, we wanted to create the largest surface area possible in order to increase the air resistance on the trash bag, which would make it fall more slowly. Thus, we decided to gather the tips of the sticks and generate the three equal parts of a circle by putting them 120 degrees apart. (We also used the plastic tape’s cover to keep the sticks together.) We wanted to forestall having it behave like a parachute, because we thought that if it rotated, it could hang in the air for a longer amount of time. We considered cutting triangular wings by cutting the trash bag from the corners i.e. on its diagonal. To make it rotate, we decided to attach one side of the wing on the stick completely to prevent the air flow on that side. However, we only attached the tip of the wing to the tip of the stick and left space for air flow. According to the plan, if we built wings in this way air resistance will cause it to spin due to allowing only one direction of air flow. In addition, we decided to cut the tennis ball into three equal parts to hang each part on three sticks so we could distribute the weight and prevent it from flipping.
To test our design, we dropped it off the balcony of Alice Paul numerous times.
Final drop time
Our final drop time off the second floor of Hicks was 3.91 seconds (with a possible error of 0.2 seconds in either direction).
The device did not spin as much as we would have liked. Perhaps in ideal conditions it would have done so.
Back to Ball Drop page.