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MORE ABOUT THE WIND SHAPING THE EARTH

We're going to see another example of the differences between feathers and bricks. Mark a 20 by 30 inch sheet of paper or cardboard into 1 inch squares, and tape it tightly to a table in front of an electric fan.

Place a spoonful of rice on the edge of the paper directly in front of the fan. Hold a large sheet of cardboard between the fan and the rice.

Turn on the fan. When it reaches a steady speed, remove the cardboard for 15 seconds, then turn off the fan. Measure how far the rice moved across the paper in that time and record the findings. Also record the pattern in which the rice blew; for example, whether the grains of rice stayed pretty much together, or if it spread out into a "fan" shape.

Repeat the activity, but use puffed rice instead of regular dry rice. Record the measurements and the pattern in which it blew, and compare any differences between the measurements, and the patterns in which the two kinds of rice were moved across the paper.

Do it one more time, using equal measures of rice and puffed rice. Try to find out if it is the size, the shape, or the weight of the rice that makes the difference in the distances (and the patterns) that rice and the puffed rice were blown.

Why is this activity shown as "another example of the difference between feathers and bricks?"

Many variations of this activity can be tried:

1. Test different kinds of materials (e.g., sand, sugar, salt, talcum powder, dry soil); try varying the wind power by using a larger or smaller fan, by increasing or decreasing its speed, or by changing its distance from the test material.

After we have reached some conclusions about size, shape, weight and wind force, we can check our notebooks to recall the greatest distance the dry earth particles moved in our previous test.

2. This activity can be repeated, having placed an eraser at half that distance, with the test material between the fan and the eraser. You will see that the material collects against the eraser.

When there is something in the path of the wind, the wind's speed slows down and/or it's direction is changed, and some of the material the wind is carrying is deposited in a place that is slightly sheltered from the wind or up against whatever is in the way of the wind. Do you think that sand dunes could be formed in this way?

Let's walk around the school grounds and see if we can find examples of the wind either sweeping an area clean, or depositing material carried by the wind.

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