Investigation 1A:
Precipitation and Climate

Modeling of Water Flow

  1. Adjust the Flow Parameter to another value, like 1.0. Run the model again and check the graph. Is the time better or worse?
  2. Repeat the process of modifying the Flow Parameter and checking the graph until you have chosen a parameter that matches the depth at mark #1 with the experimental time to drain.
  3. Change Water Depth to the height of mark #3. Run the model and read the time value that corresponds most closely to the height of mark #2. Are the numbers close?
  4. Try again, by changing Water Depthto the height of mark #4. Run the model and read the time value that corresponds most closely to the height of mark #3. Are these numbers close?
  5. From the same graph (with water depth set equal to mark #4), read the time value that corresponds to the height of mark #1. How does this compare to the final test value?

    The best test of a model is whether it can actually predict the results of experiments before they happen!

    For our first prediction (case one), we will predict how long it will take for the tube to drain from 10 cm below mark #4 to 10 cm below mark #3, both of which we will have to measure and mark. This is called an interpolation because we are trying to determine a value that is between two of our experimental values ("inter" means "between"). You could make a good guess by estimating between the two corresponding results. We can also use the model!
  6. How would you do this?
  7. What is the computer model prediction for case one?
  8. or our second prediction (case two), predict how long it would take for the tube to drain down to mark #1 if it was drained from the very top. This is called extrapolation, because we are trying to determine values that lie outside of the boundaries of what we have measured. In this case it is much harder to make an estimate: how would you make an estimate here? It is probably much better to use the model.
  9. What does the computer model predict for case two?

    Experimental Verification
  10. Measure and temporarily mark 10 cm below mark #4 and mark #3.
  11. Repeat the 'drain and time' process from the experiment (but only once!), timing water level between the two marks. Record the results. How do they compare to the interpolated prediction of case one?
  12. Fill the tube to the top. Repeat the 'drain and time' process from the experiment once again, but note that this will require a little more coordination with the start times. Time until the water reaches mark #1. Record the results. How do they compare to the extrapolated prediction of case two?

    13.