Pairs of students measured the time it took for a Teflon ball to fall 15 centimeters through oils of known and unknown ISO viscosity values. Time versus ISO value for the three known samples were plotted and a best fit straight line drawn through them. Finally, the times measured for the two unknown samples were compared with that line to determine the ISO values for those samples. We attempted to measure the drop times for the steel ball. Few teams had enough time to complete those trials, and the elapsed times were so short that the results were undependable.
One of Tuesday's team's completed worksheet follows:
One of Tuesday's team's completed worksheet follows:
The actual ISO values are 68 for the oil in the gray tube, and 22 for the oil in the black tube. The students did very careful work, successfully accomplishing an activity designed for much older students. Since we obtained more than 25 results for both gray and black tubes, we have the opportunity to do a little statistical analysis on the students' results.