Aquatic Field Investigation
Materials and Methods 1
Current Speed



At this station, your team will calculate how fast the water in your aquatic site is flowing (the current speed). Scientists are interested in current speed because of its relation to the mixing of oxygen from the air with water. As the oxygen dissolves in the water, organisms that live in the habitat can use it. Generally a fast current is better able to support more kinds of life.

In this Experiment and those that follow, you will conduct "Pre-Field" Experiments in the classroom to prepare for the Field Experiments at the aquatic site. At the aquatic site, an adult leader will guide your team through the field stations and will make sure that your team's data are recorded on Master 4a, "Baseline Study and Possible Human Impact Assessment Form." You will use this form to record all of your measurements in the field. Before beginning any of the Experiments, take a few minutes to look over the form to see the type of data you will be gathering.

Materials

For the Pre-Field station:

For the field station:

Methods

Pre-Field Experiment:

  1. In the classroom-or another large area such as a gym-measure a distance of 12 meters (about 39 ft) on the floor with a meter stick. Use chalk to mark the beginning and end of the 12 meters.
  2. Label one end of the measured distance "Point A" and the other "Point B."
  3. Have one of your team stand at Point A and another at Point B. The two students now form an imaginary "line," which you can call A-B.
  4. Have a third team member roll an orange along the imaginary line, making sure the orange is rolling along the floor before it reaches Point A and after it passes Point B.
  5. As the orange rolls past Point A, the team member at Point A calls out "Start!"
  6. A fourth team member holds a stopwatch and starts timing as soon as the word "Start!" is heard.
  7. As the orange rolls past Point B, the team member at Point B calls out "Stop."
  8. The stopwatch-keeper stops timing and calls out the number of seconds the orange took to pass from A to B.
  9. Write down in your JASON Journal the amount of time recorded by the stopwatch.
  10. Repeat steps 4-9 several times-five would be a reasonable number. Allow other team members a chance to roll the orange, run the stopwatch, and call out the "Start" and "Stop" commands.
  11. Use the following formula to calculate the speed of the orange from Point A to Point B:

    Speed = Distance/Time

    Example:
    If the orange traveled the 12-meter (1,200-cm) distance along line AB in 25 seconds, you would divide 1,200 (the total distance) by 25 (the total time) to come up with a speed of 48 cm per second.

  12. Now calculate the average speed of the orange. (The average speed is the sum of all recorded speeds divided by the number of times the speeds were recorded.)

    Example:
    If you perform this Experiment three times and record speeds of 48, 45, 43, 46, and 47 centimeters per second, the average speed would be (48 + 45 + 43 + 46 + 47) / 5 = 45.8 cm/sec.

    Field Experiment

    1. Measure a distance of 12 meters (about 39 ft) along the bank of the water.
    2. Determine which way the water is moving. Then designate the "upstream" end of the 12 meters (the end from which the water is flowing) as Point A and the downstream end (the end toward which the water is flowing) as Point B.
    3. Have one of your team members stand at Point A and another stand at Point B.

    4. Have a third team member stand upstream from Point A and drop an orange into the water so that it floats by both Points A and B.
    5. Duplicate steps 5-12 from the Pre-Field Experiment above, recording the data on Master 4a.

      Conclusions

      After you have conducted both the Pre-Field and Field Experiments, discuss the following questions within your research team and record your answers in your JASON Journal.
      1. How can the speed of a current be calculated and what does it indicate?
      2. What new questions does your group have regarding current speed and what it indicates?
      3. Look for more answers to the reason why current speed is important to the health of an aquatic site in the JASON Online Systems, the library, and science textbooks.


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        Gene Carl Feldman (gene@seawifs.gsfc.nasa.gov) (301) 286-9428
        Todd Carlo Viola, JASON Foundation for Education (todd@jason.org)
        Revised: 3 Nov 1995