http://www.ck12.org Chapter 4. Motion and Forces
FIGURE 4.59
- The depth (distance from top to bottom) of the atmosphere is greatest at sea level and decreases at higher
altitudes. With greater depth of the atmosphere, more air is pressing down from above. Therefore, air pressure
is greatest at sea level and falls with increasing altitude. On top of Mount Everest, which is the tallest mountain
on Earth, air pressure is only about one-third of the pressure at sea level.
How We Use Air Pressure
The pressure of air in the atmosphere allows us to do many things, from sipping through a straw to simply breathing.
You can see in theFigures4.60 and 4.61 how we use air pressure in both of these ways.
FIGURE 4.60
When you first suck on a straw, you remove air from the straw, so the air
pressure in the straw is lower that the air pressure on the surface of the
drink. A fluid always flows from an area of higher pressure to an area of
lower pressure, so the drink moves up the straw and into your mouth.