An Activity for a Breezy Day: Make an Anemometer

An anemometer is a scientific tool used to measure wind speed.

Wind plays an important role in many natural habitats. Some plants, especially grasses, depend on wind to assist in pollination. (It is this pollen floating in the air that give many people seasonal allergies.) Once pollinated, many more types of plants depend on wind to help spread their seeds.

Exactly how windy it is important for many different jobs. Wind speed can help meteorologists predict weather patterns and ornithologists predict when birds will migrate. If the winds are extremely strong, it might make a pilot determine it is safest to cancel a planned flight, a recreational kayaker decide to return to land or even your parents decide a picnic should be moved indoors. Wind speed also plays a role in sports. The strength of the wind can be the difference between hitting a foul ball or a homerun.

Here’s how to make your own anemometer.

Materials

• 4 Dixie cups

• A marker

• 2 straws

• Tape

• A stapler

• A pin or tack

• A pencil with an eraser

• Modeling clay

Instructions

1. Cross the straws to make a plus sign with equal lengths in every direction. Use tape to hold the straws together.

2. Place a pin through center of the cross.

3. Use a marker to make one cup different from the rest.

4. Staple the cups to the edge of straws so the cups are hanging sideways.

5. Attach the pin to the pencil’s eraser.

6. Stick the other end of pencil in modeling clay so your device stands freely.

You can test out your anemometer by blowing on it, softly or strongly, setting it in front of a fan at different speeds or taking it outside on a windy day.

To get a reading from your anemometer you will count rotations during a given time period. That is why you marked one cup to stand out from the rest. Count each time you see the marked cup in 30 seconds, then double the number of rotations. That will give you the RPM, or rotations per minute, of your anemometer. So if you counted 10 rotations in 30 seconds, 10 + 10 = 20, so your RPM would be 20.

If you are using it outside, you can compare your results to the wind speed (measured in mph, or miles per hour) of the day, which can be found in most weather reports. You can use this chart for estimating wind speed. It was developed in 1805 by British admiral Sir Frances Beaufort to help sailors, and it is still used today. It gives visual clues to help you estimate wind speed. You can use this chart along with your anemometer to estimate how your RPMs translate into mph.

Keep a journal and record the day and the wind speed. Once you have many days logged, you can count your RPMs and see if you can make an educated guess of wind speed in mph.

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