EDC Bungee Bear 2017 Kathleen and Sophia

OUR DATA

Did the bear hit the ground?

no

Did the bear hit the overhang?

no

Did the cord stay intact?

yes

What was the lowest point?

1.5< OUR LP<2

Did the cord use all possible materials?

yes

How many times did the bear bounce?

2 times

How high did the bear go on the first bounce? (bonus)

over 2m

OUR GROUP'S SUCCESS/FAILURES

Our cord was successful because of the labs and excel spreadsheet. The labs helped us review past information that we learned and built the basis of how we would construct the cord. The spreadsheet was especially helpful because it did all of the math and calculations for us so that we could trust the cord. However, our original design had to be changed once we built it because the spring constant was smaller than the one we had calculated prior. To make up for it, we added more strands and took away 2 elastics in each strand (this increased the spring constant to the one we found in the labs).

Although we met most of the success criteria, our main failure was the fact that Bungee Bear did not come as close to the ground as we had hoped-

When we used the spreadsheet for this design, it told us that the bear's low point would be a little over half a meter. This was not the case.

What happened?

We were so worried about the spring constant matching our calculations that we shortened both the fixed cord and strands of elastics. In the end, this made it so that the bear could not get as close to the ground as we would have liked. Though the spread sheet shows it being successful, when we tested the constant using the force sensor and shortened the strands, we did not put those values back into the spreadsheet. This resulted in us not being aware of how short the actual bungee was.

Our original design specs. When tested, the spring constant was much lower than 48N/m so we added more strands and decreased the amount of elastics in each strand.
Our final design specs. As you can see, we got the spring constant closer to what we wanted to use but changed the lengths of the fixed cord almost 30% and the elastic 15%.

How can other groups learn from us?

If we could redo the whole process we would be more careful about testing our designs and making sure it matched up with what we wanted to accomplish. Overall, we had success with our bungee, but more careful consideration before drop day would have helped. We were quickly trying to construct a better design based on how it tested and did not realize that it may not have been long enough/had enough stretch to give the bear enough "thrill."

As for our class success criteria, the rubric itself was well put together and allowed groups that may not have done well in some parts, do well in others. The bonus also helped us a lot, as the bounces of the bear got us some extra points that we had lost for lack of a thrilling low point.

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