Casa di Mir Summer Mathematics: Adventure #6

Let’s Go Fly a Kite!

Have you ever made a kite before? There are many different models of kite,s and even small children can make some of the easier models with help from a parent.

An excellent resource for do-it-yourself kites is The construction of your own kite is not only immensely satisfying, but it provides experience in many of the practical skills needed for success in mathematics: following directions, measuring and cutting, putting things together, working on precision, and troubleshooting and persevering when things don’t work out quite right. Try the Tiny Tots Diamond kite for your littlest kid. Try the Diamond, Delta, or Sled kite for your older kids – or yourself!

Wind Speed. Kite-flying is generally most successful on a day with wind speeds in a certain range – and that range is different for different kite shapesHow does one measure wind speed though? 

Speed, in general, is what we call a derived measure, because we don’t measure it directly. To find the speed of a moving object that we can see, we measure two things simultaneously: the distance it travels and the time it takes to travel that distance. The object’s speed is the ratio of distance traveled to time elapsed. For example, measuring the speed of a miniature die cast car that’s hurtling down a straight track is quite manageable. Just measure the length of the speed zone using a ruler or tape measure and measure the time it takes the car to traverse the speed zone using a stopwatch. Measuring a person’s walking, running, skipping, or cartwheeling speed is similarly manageable.

But wind is invisible! How did human beings figure out a way to measure the speed of wind?!?!

There are a number of clever devices called anemometers that, in essence, make wind speed visible, which allows us to use our strategies for determining speed of visible objects. An early simple anemometer, invented in 1845 by John Robinson, an Irish astronomer and physicist, looked like a whirligig with four cups mounted sideways on horizontal arms that were attached to a vertical shaft. Your child can make an anemometer using small paper cups, straws, a pencil, and a push pin.  See the article Measure Wind Speed with Your Own Wind Meter from Scientific American for directions.

You and an older child can calibrate your anemometer in the following way. First, color one of the whirligig cups. This helps in counting number of rotations. On a windless day, drive across a large empty parking lot or seldom-traveled road at 10 miles per hour. Have an older child hold the anemometer out of the window and count the number of rotations in 30 seconds. This number of rotations in 30 seconds will correspond roughly to the wind blowing at 10 miles per hour. 

Now, you have a homemade wind meter. You can always check to see if the wind speed is in the right range for your favorite kite.

The Berkeley Kite Festival. For a WOW kiting adventure, make plans to attend the Berkeley Kite Festival on July 29th and 30th from 10 am to 6 pm at Cesar Chavez Park at the Berkeley Marina. You can attend this family-friendly event for free (although parking is $15) and see the many different and amazing ways that folks have fun with kites. See the event website for more information.

Here’s to windy days and awesome kite flying adventures!

About the author: Trisha Bergthold has been the middle school math teacher at Casa di Mir Montessori School since 2014. She holds a PhD in mathematics with emphases in curriculum and pedagogy. Prior to her work at Casa di Mir, she designed curriculum for kindergarten through college level. She also taught university-level mathematics courses for sixteen years.

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