When the arrow of a weather vanepoints west, the wind is blowing from the west.
Explanation: Under the influence of the wind, the weather vane rotates around the vertical axis, causing the tail of the wind to swing in the direction of the wind and the head to point in the direction of the wind. So the title says "the arrow of the weather vane points east", and the head points towards the direction of the wind, so "when the arrow of the weather vane points east, the wind blows from the west" .
Basic principle:
When the wind direction reaches a certain angle with the weather vane, the wind exerts pressure on the weather vane. This force can be broken down into two wind forces. parallel and perpendicular to the weather vane. Since the wind receiving area of the weather vane head is relatively small and the wind receiving area of the tail is relatively large, the felt wind pressure is not equal. The prWind pressure perpendicular to the tail produces wind pressure. moment, rotating the weathervane around the vertical axis until the head of the weathervane faces the wind. When the weather vane is pointing in the direction of the weather vane, the weather vane is stable in a certain direction due to the forces on both. the sides of the wing plate are balanced.
The arrow of the weather vane always points towards the source of the wind. The principle is actually very simple: the wind receiving area of the tail of the arrow is larger than the tip of the arrow. and the tail of the arrow are subject to the wind, the tail of the arrow will be pushed back by the wind, causing the arrow to move towards the source of the wind.