Question

Which is correct about Atmospheric pressure? a) Pressure remains uniform at different altitudes
b) Low pressure promotes divergence of air
c) Wind blows from high to low pressure d) Low pressure gradient is a result of rapid change of pressure with unit distance

Answer 1

Answer:

Air exerts a force on surface of objects.

A. Air pressure is force per unit area.

B. It is cumulative force of a multitude of molecules.

C. Pressure depends on:

1. Mass of molecules

2. Pull of gravity

3. Kinetic energy of moleculesII. Normally a pressure balance between air and objects.

III. Pressure decreases with height.

A. Max air density occurs at surface.

B. Air becomes "thinner" with height.

C. Affects on humans:

1. Dizziness, headaches, shortness of breath in mountains

2. "Ear-popping"IV. Horizontal variations in pressure

A. Altitude dependent, but this is corrected to sea-level

B. After corrections, still are variations because:

1. Different air masses

2. Air is compressible

Explanation:

. Air mass - huge volume of air that is relatively uniform in temperature and water vapor.

1. Pressure increases with warmer temperatures (in closed container)

2. But atmosphere has no walls, so heated air expands, becomes less dense. Thus, net result is that pressure actually decreases when heated.

a. Greater activity of the heated molecules increases the spacing between neighboring molecules and thus reduces air density. The decreasing air density then lowers the pressure exerted by the air. Warm air is thus lighter (less dense) than cold air and consequently exerts less pressure.

3. Moist air is less dense than dry air!!

4. Sinking air increases pressure at surface, and ascent decreases pressure at surface.

5. In addition air pressure changes caused by variations of temperature and water vapor content, air pressure can also be influenced by the circulation pattern of air.V. There is pressure variations at