Calculating the wind speed is a simple experiment that can be done with a few materials. This experiment will step you through making an anemometer and calculating the wind speed based on data collected.
Building the Anemometer
Cut off the top lip of the cups.
Staple the cardboard strips together, forming a cross. Measure to make sure that each arm of the cross is the same length.
Staple each cup to the ends of the cardboard strips. Make sure that all cups, including the red cup, are facing the same direction. They will form a circle of cups when done.
Stick the center of the cross to the top of the pencil eraser with a pin or tack.
Blow into the cups to make sure that they spin freely in wind. Adjust as needed so that they move easily.
Calculating wind speed
Take your anemometer out into the wind. Hold it above your head, but where you can still count the number of rotations.
Count the rotations of the red cup over 30 seconds.
Multiply the number of rotations by the diameter of the anemometer in inches and divide by 168. This will give the wind speed in miles per hour.
Multiply the number of rotations by the diameter in centimeters and divide by 265 to get the wind speed in kilometers per hour.