Wind can be very powerful, especially when it moves at high speeds. But just how much faster is a strong wind compared to a gentle one? Find out by measuring wind speeds using a tool you create with paper cups, straws, a pencil, and a pin.
Wind: Movement in the air that can be seen or felt. Wind occurs when air moves from a high-pressure area (where there are more molecules) to a low-pressure area (where there are fewer molecules).
Meteorologist: A person who predicts the weather by using different tools to measure changes in the atmosphere.
Anemometer: A tool used by meteorologists to measure wind speeds.
Speed: How fast or slowly something is moving.
Revolutions per minute (rpm): How many times something goes around in a complete circle, or rotates, in one minute. The anemometer you will make in this exercise measures the wind speed in rpm.
To do this activity you will need:
Paper cups (4) that have one hole punched in them
Paper cup that has five holes punched in it (1)
Plastic straws (2)
Pencil with an eraser on one end (1)
Fan with different speeds (optional)
Take a one-hole cup and push a straw through the hole so that about an inch of the straw is inside the cup. Fold the end of the straw inside the cup and staple it to the side of the cup. Repeat this with the other straw and another one-hole cup.
Figure 1. Push a straw through two of the cups that have one hole in them and staple the straw to the side of each cup.
Push the empty end of each straw straight through two facing holes on the sides of the five-hole cup, to form an "X" in the middle.
Turn the cups so that they are facing the same direction. Why do you think the cups should face the same direction?
Figure 2. Push the empty ends of each straw through two facing holes on the sides of the cup that has five holes. Make sure the cups face the same direction.
On the empty end of each straw, push on another of the remaining one-hole cups. Turn the cup so that it faces the same direction as the other cups. Again, fold the end of the straw inside the cup and staple it to the side of the cup.
Gently pull or push the cups so that they are all about an equal distance from the center of the five-hole cup.
Carefully push the pin through the two straws where they cross. You may need your teacher to help you push the pin in. Why do you think it is important that something as small as a pin be used for this?
Push the pencil eraser through the hole in the bottom of the cup with five holes. Carefully push the pencil in until the eraser touches the straws.
Carefully push the pin into the eraser. You may need your teacher to help you push the pin into the eraser.
Figure 3. After attaching cups on the empty ends of the straws, then pinning the two straws together along with the pencil eraser, you will have a complete anemometer that is ready to measure wind speeds.
Holding your anemometer upright by the pencil end on a desktop or table, sit down and blow very gently into the cups on your anemometer for a few seconds, and then try blowing harder. How did blowing harder change how the anemometer turns? If you begin to feel light-headed or dizzy, stop blowing and catch your breath.
If your classroom has a fan that has different speeds, hold your anemometer in front of the fan at different speeds. At the different speeds, count the number of times one of the cups completely rotates around the anemometer in 15 seconds (using a timer or clock). Multiply this number by four (four times 15 seconds is equal to 60 seconds, or one minute). This calculation will give you the revolutions per minute (rpm) of your anemometer for that "wind" speed.
If you used a fan, how did the rpm change when you held your anemometer in front of the fan at a slow speed compared to a faster speed? Did it change as you expected, or was it different than expected? Do you think the rpm would be greater if you used your anemometer outside on a very windy day compared to using your anemometer in front of the fan set at a fast speed?
Why do you think a faster wind would make the anemometer spin faster?
You can find this page online at: http://www.sciencebuddies.org/science-fair-projects/Classroom_Activity_Student_WindMeters.shtml
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