Wind and Pressure


Demonstratation of the effect of velocity of air on air pressure

Air velocity can be measured by sensing the pressure produced by the movement of the air. This application note will describe the basic relationships between air velocity and the pressure generated by air flow. Anyone who has put their hand out the window of a moving car has experienced the force applied by moving air.
The pressure developed by the air velocity is called the velocity head, and it is affected by the density of the air. The density of the air, in turn, is a function of the local atmospheric pressure and the temperature. The equations that relate all these factors are:
V= velocity d= air density, Pa= Barometric pressure,  T= Air temperature , dp= pressure reading. 


Activities to show air movement from high pressure to low pressure

Fountain Bottle
  •  Fill a 2-liter soda bottle half full of water.
  •  Take a long straw and insert it in the mouth. Wrap a lump of clay around the straw to form a seal.
  •  Blow hard into the strawthen stand back. Your blowing increases the air pressure inside the sealed bottle. This higher pressure pushes on the water and forces it up and out the straw.
This happens as the air pressure inside the bottle increases by blowing and the air pressure outside the bottle is less in comparison.Hence the air started flowing from inside to outside of bottle along with the water.