GRAND RAPIDS — Meteorologist talk about wind speed all the time but do you know which tool they use to measure it? In today's weather experiment we are going to learn about measuring wind speed with an anemometer which is the tool meteorologist use to do so. Lets get started!
What you need:
- 5 paper Dixie cups
- 2 soda straws
- Paper punch
- Sharp pencil with eraser
Step 1: Take 4 Dixie cups and use your paper punch to punch one hole in each cup about a half of an inch below the rim
Step 2: Take the fifth cup and punch 4 equally spaced holes about a quarter of an inch below the rim. Then punch a hole in the center of the bottom of the cup
Step 3: Take one of the 4 cups and push a soda straw through the punched hole. Fold the end of the straw and tape it to the side of the cup across from the hole. Repeat this step another one punched cup and second straw
Step 4: Slide one cup and straw piece through two opposite holes in the cup with 4 holes. Push another one-hole cup onto the end of the straw you just pushed through the 4 hole cup
Step 5: Bend the straw and tape it to the one-holed cup making certain that the cup faces the opposite direction from the first cup. Repeat this process using the other cup and straw assembly and remaining one-hole cup
Step 6: Align the 4 cups so that the open ends face in the same direction either clockwise or counter clockwise around the center cup
Step 7: Push the straight pin through the 2 straws where they intersect
Step 8: 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
Step 9: Go outside on a windy day and measure how fast the wind is!
An anemometer is the instrument we use to measure wind speed! Its useful because it rotates with the wind.
If you want to calculate how fast the wind is going you have to figure the velocity at which your anemometer is spinning and determine the number of revolutions or spins around per minute your RPM. Best way to do this is mark one of the cups with a colorful piece of tape or if you have some different colored Dixie cups use one that is a different color. This makes it easier to count how many times around the cups have spun.
To determine this you first need to calculate the circumference of the circle made by the rotating cups by measuring the distance around the circle that they made. Use a tape measure or a ruler to do so. Then convert this to miles by dividing the number of inches by 12 to get feet and then dividing that number by 5,280 (the number of feet in a mile). Multiply this number by the rpm. Finally divide your product by 60 to convert to hours. You will have an approximate velocity at which your anemometer is spinning in mph. This does not take into account friction or drag.
The local different in temperature and pressure causes local winds. There are 4 types including hot, cold, convectional and slope.
Air is made up of tiny molecules and when those molecules are heated they move faster. So when the air is heated its molecules move faster and become spaced farther apart which makes the air less dense. This also means that the air had a lower overall pressure. In comparison, cold air is made of more tightly packed molecules and is denser with relatively higher pressure.
Air pressures are inclined to balance out so when there is an area of lower pressure the surrounding air in the higher pressure areas move in. This movement of air from high to low pressure is what generates wind.
So there you have it! We just made a anemometer! Send our meteorologist Candace Monacelli your pictures doing this experiments at home! She will feature future meteorologists on my Facebook page daily!