Anemometer is blowing on the back of the cup on the opposite end of the cross. Since a hollow hemisphere has a drag coefficient of .38 on the spherical side and 1.42 on the hollow side, more force is generated on the cup that is presenting its hollow side to the wind. Because of this asymmetrical force, torque is generated on the axis of the anemometer, causing it to spin. Theoretically, the speed of rotation of the anemometer should be proportional to the wind speed, because the force produced on an object is proportional to the speed of the fluid flowing
Does exactly what it says on the tin began a similar copycat advertising campaign in Ireland stating that its product "does exactly what it says on the tube". The phrase is a registered trademark of the Sherwin-Williams Company, the owner of Ronseal, across the European Community for products including paints, varnishes, and wood preservatives (E3085826). In 2007, a song titled "What It Says on the Tin" was released by the British singer Katie Melua. Although the song is about relationships, the phrase has a similar meaning. Does exactly what it says on the tin "It does exactly what it says on the tin" was originally an advertising slogan