SimuLab 4: One-Dimensional Random Walk

Now do the same activity using the computer. Please see the Java Applet Page.

1. Bring up the Random Walk program and choose Rand Walk from the New box on the control panel.


2. Take one step at a time by pressing the Flip button.


3. Now make the computer flip coins automatically using the Go button.


4. Do the 10-step random walk 10 times (see Figure ).

Figure 3.5: Distribution resulting from 20-trial random walk.


5. Press Coin Flip to start a new screen, select Less Graphics under the Options menu, and press Go. The program will run 100 trials of 10 steps each.


6. When the 100 trials are finished, do a third 10-step random walk choosing 500 trials, under the Experimental menu and Less Graphics under Options.

Q3.15: Are there any similarities among the bar graphs in the three runs?

Q3.16: Does a larger number of trials make it easier to describe the shape of the resulting bar graph?

Q3.17: If you were shown only the bar graph, could you tell whether it came from the Random Walk part of the program or the Coin Flipping part of the program?

Q3.18: Why are there spaces between the bars in the bar graph for Random Walks, when there were no spaces between the bars for Coin Flip?

Why is the random walker important? One reason the random walker is important is because it mimics the way a molecule moves. We want to study not only the motion of a single molecule, but also the motion of many molecules that combine to form the chemical and physical processes we observe every day. To do this, we need to watch many walkers at the same time.

Q3.19: Can you think of scientific or natural processes whose underlying physical or chemical dynamics could be described by a random walk?

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