An anemometer is an instrument used to determine the wind's force or speed. The Wright brothers used an anemometer to determine the wind's speed as they experimented with their flying machines.

You will build one type of anemometer called a cup anemometer. You will test the anemometer under different wind conditions, record and graph your results.

STEPS TO FOLLOW:

Read the history information for this activity. This cup anemometer is an example of a vertical-axis wind collector.

Take four of the paper cups. Using the paper punch, punch one hole in each, about a half inch below the rim. (You can use the ruler to measure this.)

Take the fifth cup. Punch four equally spaced holes about a quarter inch below the rim. Then punch a hole in the center of the bottom of the cup.

Take one of the four cups and push a soda straw through the hole. Fold the end of the straw, and staple it to the side of the cup across from the hole. Repeat this procedure for another 1-hole cup and the second straw.

Now slide one cup and straw assembly through two opposite holes in the cup with four holes. Push another 1-hole cup onto the end of the straw just pushed through the 4-hole cup. Bend the straw and staple it to the 1-hole cup, making certain that the cup faces in the opposite direction from the first cup. Repeat this procedure using the other cup and straw assembly and the remaining 1-hole cup.

Align the four cups so that their open ends face in the same direction (clockwise or counterclockwise) around the center cup. Push the straight pin through the two straws where they intersect. Push the eraser end of the pencil through the bottom hole in the center cup. Push the pin into the end of the pencil eraser as far as it will go. Your anemometer is ready to use.

Take your anemometer outside. Watch it spin as the wind strikes it. Your anemometer is useful because it rotates with the wind. It need not be pointed into the wind to spin.

Make a small mark on one of the cups. Record the number of times that cup makes a complete revolution (a complete cirle) around the vertical-axis (pencil) in a minute. This number will be the revolutions per minute or RPM. Record your results on this data collection sheet. Try this at different times in a day or on different days. Record the wind conditions such as: no wind, light winds, medium wings, heavy winds, very heavy winds. Is there any pattern that you observe? Does the anemometer spin faster in the morning, afternoon or evening?

Plot your results on a graph. What conclusions can you draw?