Scientists use an anemometer to clock wind speed. This is an
easy experiment that will give you an approximate wind speed reading.
We suggest not using it for hurricane-force winds—it’s
built using coffee cups, for goodness sake!
For a printable version of this project, click
here.
Materials
• Four small Dixie or
Styrofoam coffee cups
• Coffee cup with lid (or a milkshake cup with lid)
• Ball-point pen (sharp enough to pierce Dixie cups)
• Small piece of scrap wood to hammer on
• Five wide “milkshake” straws
• Scotch tape
• Big nail
• Felt pen
• About a cup of sand
• Watch
• Fan (optional)
Instructions
1. Insert the end of one straw
into the end of another straw. Do the same thing with two more straws.
You will now have two “double-length” straws.
2. Use your two long straws to make an “X”(they
should meet at their junctions). Use Scotch tape to hold your X
together.
3. Use the pen to poke two holes near the base of a Dixie cup
(see photo). Do the same to the remaining three cups.
4. Pass the end of a straw through the holes of a Dixie cup
(it should fit pretty snugly). Do the same with the other three
cups and straw ends. Turn the cups so they are all facing in the
same direction around the “circle”.
5. Secure each cup to its straw end using Scotch tape.
6. Using your scrap wood—and with an adult’s help
because it can be slippery—hammer the big nail through the
centre of the X.
7. Fill up the coffee cup halfway with the sand. Put on the
lid. Stick the remaining straw through the lid’s middle right
into the sand so it sticks up straight.
8. Place your X onto the coffee cup by putting the nail inside
the straw.
9. With a felt pen mark an X on one of the cups.
10. Place your wind gauge in the wind or in front of a fan.
11. Use a watch to count the number of times the marked cup
spins around in one minute.
What’s
Happening
You’re measuring wind speed
in revolutions per minute (rpm). To convert to kilometres per hour,
you first need the radius of your anemometer (the distance from
the nail to the centre of one of the cups). The radius must be in
metres, so if your radius is 9 cm, use .09 m. Now plug your values
into this formula:
rpm radius 377
÷ 1000 = speed
For example, if your cups spin around 100
times in one minute, and your radius is 9 cm, the calculation would
look like this:
100 .09 377 ÷ 1000 = 3.393 km/h
