|photo by Denise Toth|
They were then given the data from the control rocket's launch as a means of comparison. The clinometer readings are not perfectly accurate, however if the data from a student's launch indicates that the rocket flew more than 2 meters higher than the control rocket, it probably did fly higher. Otherwise, it is best to conclude that they flew about the same height.
Each student then made up a one sentence conclusion that stated what they learned from the experiment about how to make rockets fly higher. Once they were finished, each student got up in front of the class and described the one difference between their rocket and the control rocket. They also showed the class their rocket. They told the class the hypothesis of their experiment and then the results of the experiment on the graph. Lastly, they read their one sentence conclusions. The other students were allowed to ask questions but I tried to keep the focus on what variables might not have been controlled. Sometimes the other students were able to suggest ways to improve the wording so that everyone could agtagree with the student's conclusion, and perhaps ways in which the experiment might be improved in the future.
In conclusion, we summarized the results of all the experiments. Two students did similar experiments but got different results and so we attempted to explain what unknown variables could have affected the two experiments. Suggestions included that perhaps they were made slightly differently despite the effort to make them identical. Another suggestion included the possibility of a gust of wind that might of affected one of the rockets.
I reminded the students that the scientific method requires many repeated experiments over a long period of time before a final conclusion can be drawn.
Some of the conclusions we came to?
We found that odd number of fins, 3 and 5 flew better than 4 fins. Fins add weight so the 3 fins flew well, but when you have 5 fins the rocket flew better because of the increased stability. The four fins had added weight but not as much added stability, so was the worst of lot.
Fins that pointed down worked the best. We assume that this helps to reduce the airflow drag.
Shorter rockets flew high because of the reduction in weight, but had less control with its flight path, so their actual height attained varied.