The Motion Harbor Exhibit
The Children's Museum planned a Motion Harbor exhibit. Visitors would move one end of an elastic cord to send repeating waves toward a light ring resting on the cord. The team measured wave height from the resting level up to a crest. They measured crest spacing from one crest to the next crest along the cord. A model showed the cord's pattern, but it did not show the ring's motion unless the team added that information.
The team made three wave models. In Model A, the resting level was 5 units. Crests reached 8 units, troughs reached 2 units, and neighboring crests were 8 centimeters apart. In Model B, the resting level was 5 units. Crests reached 9 units, troughs reached 1 unit, and neighboring crests were 8 centimeters apart. In Model C, the resting level was 5 units. Crests reached 8 units, troughs reached 2 units, and neighboring crests were 4 centimeters apart.
The team then tested the cord and ring. Test P used the pattern of Model A. The ring moved up and down 6 centimeters and moved 1 centimeter sideways. Test Q used the pattern of Model B. The ring moved up and down 8 centimeters and moved 1 centimeter sideways. Test R used the pattern of Model C. The ring moved up and down 6 centimeters and moved 1 centimeter sideways. In Test S, the cord was held still instead of sending waves. The ring moved 0 centimeters up and down and 0 centimeters sideways.
The team kept the same cord and ring for the tests. They measured the ring from its lowest position to its highest position for the up-and-down distance. They wanted a model that showed both the repeating wave pattern and the way the ring moved as waves passed.