when the wind blows,this spins?

Answer 1

Anemometer:
An anemometer is a device for measuring the velocity or the pressure of the wind, and is one instrument used in a weather station.
The simplest type of anemometer is the cup-anemometer, invented (1846) by Dr. John Thomas Romney Robinson, of Armagh Observatory. It consisted of four hemispherical cups each mounted on one end of four horizontal arms, which in turn were mounted at equal angles to each other on a vertical shaft. The air flow past the cups in any horizontal direction turned the cups in a manner that was proportional to the wind speed. Therefore counting the turns of the cups over a set time period produced the average wind speed for a wide range of speeds.

Answer 2

weathercock