Air Pressure
Air pressure is the force exerted per unit area of surface by the air that is directly
above that surface.
Imagine a sealed container full of air as shown below. When the molecules of air
collide with the inside surfaces of the container they exert a pressure. The amount of
pressure they exert depends on the number of collisions that occur between the
molecules and the inside surface of the container. We can change the pressure in two
ways. First, we can increase the density of the air by either putting more air
molecules into the container (A) or reducing the volume of the container (B).
Secondly, we can
increase
the
temperature
of
the air (C) to
make
the
molecules
move
faster and thus
collide with the
sides more often.
Therefore,
changes in air
A
B
C
pressure can come
about by changes
in air density or
temperature.
Air pressure is measured using a barometer.
Some applications of Air Pressure:
¾ Cycling against the wind is difficult because of the pressure exerted by air.
¾ The tires of vehicles are filled with air, thereby exerting pressure. This makes it
easy for them to hold and carry the weight.
