– Drinking straw (use a straight straw, or cut off the bendy part)
– Pencil with a new eraser
– Straight pin (or a paper clip could work)
– Poster board or card stock
– Plastic cup
– Sand, salt, or pebbles
1) Cut out a square and a triangle from the poster board or card stock, each about three inches across. Cut a slit in each end of the straw and insert one shape in each slit.
2) Fill the plastic cup with sand, salt, or pebbles. Stand the pencil upright in the cup. Push the straight pin through the center of the straw and into the pencil eraser. The straw should be able to rotate freely in the wind!
3) Place your weather vane outside, away from buildings, trees, etc. and see what happens when the wind blows.
How It Works
When the wind blows, it pushes the larger surface of the vane (the square). As a result, the other end (the triangle) points into the oncoming wind. So if the vane points east, the wind is coming from the east.
Real World Application
Weather vanes can be of some assistance with forecasting weather. For instance, here in the Northern Hemisphere, wind from the North generally brings colder weather; wind from the South generally brings warmer weather; wind from the East may bring precipitation; and wind from the West may bring clearer weather.