Real-Life Math
It's particularly important for navy divers to understand how
different forces act upon their bodies when they are underwater. Most recreational
divers do their diving close to home, occasionally splurging on a diving vacation
in exotic locales such as Australia's Great Barrier Reef.
By contrast,
navy divers are constantly adapting to different and often unpleasant underwater
environments. A navy diver may be working in the swampy jungles of Vietnam
one week and the frigid waters of the Arctic Ocean the next.
Factors
such as the water temperature, the height of the current and even the number
of feet they are above sea level all affect how long a diver can remain underwater.
You
are in charge of training a group of enlisted men and women to scuba dive.
You are conducting a training exercise at a freshwater lake. The purpose of
the exercise is to demonstrate to the group how differences in altitude affect
them when they are diving.
Since they will be diving to 150 feet, they
will need to calculate what the total pressure will be on their body at this
depth.
This should be a simple problem for this group, since they have
almost completed their training. They know that the total pressure that is
exerted on the body when they are diving is a combination of air pressure
and the water pressure between the surface of the water and the depth they
are diving at.
Total Pressure = Air Pressure + Water Pressure
Air
Pressure
They also know that, anywhere in the world, there is
100 miles of air above your body when you are standing at sea level. This
helps them to determine the air pressure at this elevation.
| Air Pressure = | 1 atmosphere x (100 miles - elevation)
1 00 miles |
(An atmosphere is a basic unit of measurement. One atmosphere
is the weight of one square inch of the atmosphere at sea level.)
Water
Pressure
Since this is a freshwater lake, you explain that one
square inch of freshwater that is 34 feet in height exerts a pressure equal
to one atmosphere. This helps them to determine the water pressure.
Water
Pressure = 1 atmosphere x (depth / 34)
There is one final
piece of information the group needs to complete the calculation -- the elevation
of the lake. You tell them that it is 3,500 feet above sea level
and wait for them to perform the calculations.