One of the best ways to involve your family in science and learning is to talk about and study the weather. No matter where you live there is something to observe and measure. It is fun to make your own weather observation tools. The information may not be as complete and accurate as the real thing, but as a family or school project, it’s perfect.
At home you will be replicating the very first and most basic anemometer that was built by Leon Battista Alberti. Although he did not use the same simple items, the design and results will be very similar. He built his cup anemometer in 1450. It is used to measure wind speed or velocity.
To make your own anemometer you will need a sharp pencil with an unused eraser, a ruler, stapler, 5 three ounce paper cups (Dixie Cups work well), 2 soda straws, tape, paper punch, scissors and a pin.
Measure ½ inch down from the rim on 4 of the cups and mark it with your pencil. Use the paper punch to punch out a hole on the mark. Set those 4 cups aside.
With the 5th cup you are going to punch two holes on opposite sides of the cup directly across from each other. These should be ½ down from the rim. Two more holes need to be punched ¼ inch down from the rim, evenly spaced between the first two holes. Punch a hole directly in the center of the bottom of the cup. Set this cup aside.
*Now it is time to attach the cups to the drinking straws. Take one of the four cups and push the straw through the hole. Fold the end of the straw to create a small tab. Staple the straw tab to the side of the cup across from the hole. Repeat this process with the second cup.
Now take cup number 5 with the 4 holes to begin assembly. Slide one cup and straw assembly through two opposite holes in the cup. Now you are going to take a one hole cup and attach it to the end of the straw you just pushed through. The cup needs to face in the opposite direction of the cup on the other end of the straw. Bend the straw and staple.
Repeat from * with the other cups.
Now align the four cups so their open ends are all facing counter clockwise around the center cup. Push the straight pin through the two straws where they intersect.
Push the pencil through the hole in the bottom of the center cup, eraser first. Push the pin into the eraser as far as you can.
Now you have built the anemometer, how do you use it?
Here comes the math portion of the project. To determine the velocity at which the anemometer spins you have to determine the number of revolutions per minute. You need to calculate the circumference (in feet) of the circle that is made by the rotating cups. Then you multiply the revolutions per minute by the circumference of the cup and you have the approximate velocity. Counting the revolutions can be a challenge if the wind is high.
It is a fun weather experiment.