Air Pressure

What is it? Air Pressure: the weight of the atmosphere pushing down around you What causes the movement toward the surface? Gravity pulls air molecules toward surface How is density affected? Density increases closer to the surface Molecules above push downward on molecules below

Why don’t we feel it? Animals have become accustomed to the environment they developed in Each cell in our body pushes outward equal to air pressure pushing in Air pressure at the surface –15 lbs/in 2 –1013mb (millibars is a unit for pressure)

Deep Sea Pressure

How does Temperature Play a Role? As Temp. increases, what happens to air? Air begins to expand As that occurs, how is density affected? Density decreases as air expands So, how does temp. affect density? As temp. increases, density decreases How would the air behave if it were less dense than the surrounding air? The warmer, less dense air would rise

Relationship btwn T P & D If density stays the same (closed system)… –T increases, P increases –T decreases, P decreases If pressure remains constant… –T increases, D decreases –T decreases, D increases

High & Low Air Pressure

Pressure & Wind Due to temperature differences air can be at a higher/lower pressure Wind is caused by those dif. in pressure –Ex/ air conditioning creates cool air inside, warm air outside, air moves from in building out Warm air has lower pressure (less dense), while cool air has higher pressure (more dense) Air moves from higher to lower pressure In the atmo. Higher pressure air sinks & spreads along the ground as WIND

Pressure & Wind