Measuring wind speed
Weather forecasters, aviators, sailors, and some other people often need
to know exactly how hard the wind is blowing. To find out, they use an
instrument called an anemometer (an uh MAHM uh tuhr). An anemometer
measures the speed of the wind.
You can make a simple anemometer for yourself. You’ll need:
four paper cups two strips of heavy cardboard, 4×12 inches (10 x 30
centimeters) thin cardboard or heavy paper, 4×6 inches (10 x 15
centimeters) crayon pencil scissors
tape
long nail with a large head ruler
Measure and cut the heavy cardboard strips. Put the strips together to
make a cross, like a plus sign. Tape the strips together.
Then make a small hole in the middle of the cross and push the nail
through the hole.
Color stripes on one of the cups, so that it looks very different from
the others. Then cut two four-inch (10-centimeter) slits down the
opposite sides of each cup.
Slide one cup onto each arm of the cross. Push the arms through both
slits. The ends of the arms should stick out about 1/2 inch (12
millimeters) beyond the cups. All of the cups should face in the same
direction.
Roll the piece of thin cardboard around a pencil to make a six-inch
(15-centimeter) tube. Tape the tube together. Put the nail in the tube,
so that the cross with the cups rests on top. Your anemometer is ready
to use.
Pick up the bottom of the tube and hold your anemometer out in the wind.
The cross with the cups will spin. Count the number of times the striped
cup moves past your arm during thirty seconds.
Divide the number you got by twenty-two. This will give you the wind
speed in miles per hour. For example, if the striped cup went around
forty-four times, divide forty-four by twenty-two. You get two—so the
wind speed is two miles per hour.
To find the wind speed in kilometers, multiply your answer by 1.6. Two
times 1.6 is 3.2 kilometers per hour.
