Prepare the foam ahead of class:
Make a small hole with scissors in the end of a piece of foam and push the tube/pen cap into it. A skewer inserted into the tube allows the foam to spin freely on the skewer.
Make small holes in an egg carton cups and push a skewer through them. Hot glue the skewer in place. (Note: the skewers are a little long in the photo - push them further through before glueing.)
Students assemble their anemometer by pushing the cup skewers into the foam in a circle. Ideally the cups are all facing the same direction - help younger students to assemble, and allow older students to experiment with cup placement.
Insert a skewer (with no cup attached) into the hole that the pen cap/tube makes in the foam.
Blow into the cups to turn.
Try experimenting with different numbers of cups, and different strength of breath.
A weather station anemometer has metal cups which are weather-proof. The speed of the spinning cups is recorded as wind speed.