Physics 24 Web Project
April 11, 2004
Group Members:  Lucy Guill, Lindsy Masters, Lee Tennille, David Kleish

Purpose:  To demonstrate the importance and reveal the interesting aspects of the physics principles of buoyancy and pressure in the sport of scuba diving.

Pressure:

The pressure exerted by a fluid is defined as the magnitude of the force acting perpendicular to a surface divided by the area over which the force acts.  Pressure can be created by all fluids that have mass, including water and air.  Less water than air is required to create an equal pressure because of water's greater density.

Density:

The mass density is the mass of a substance divided by its volume.

The denisity of air is 1.29 kg/m3.  The density of fresh water is 1000kg/m3.  The density of salt water is 1027 kg/m3 because it contains salt, giving it a greater mass/unit of volume.

 At sea level we experience 14.7 pounds of pressure per square inch (psi).  This pressure is equivalent to 1 atmosphere of pressure (1 atm).  In fresh water, a diver would experience a pressure of 2 atm at 33 feet or 10.3 m.  This change is pressure greatly complication a human's process of breathing.
 
When under water, the air in a diver's lungs is being compressed by the pressure of the water above the diver.  The volume of the diver's lungs, therefore, becomes smaller, but the amount of air required by the body and needed in each breath remains constant.  For this reason, the air that a diver breaths in must be at the same pressure as the body of the diver.

A diver would not be able to breathe through a hose that provides air from the surface because this air would have a large volume, and the human lung would have to be capable of pushing the weight of water outward to provide a greater volume in the lungs for this air.

For these reasons, it is necessary to use pressurized air tanks while scuba diving.  These tanks
 
 
 
 

Buoyancy:

BUOYANCY COMPENSATOR
 Buoyancy compensator is used for changes in buoyancy.  To start
let all the air out of your buoyancy compensator but as you continue to
go downward you need to add air to your buoyancy compensator to
neutralize buoyancy.  As you start to ascend to the surface you need to
let air out of the buoyancy controller to neutralize buoyancy.  By
exhaling you loose pounds of buoyancy.  Because for every action there
is an action in the opposite direction, stated by Newton's Second Law,
so it is best to do a surface dive and then use your fins to push you
down.  It is important to keep your head down because your body will go
in the direction of your head.  Another factor influencing buoyancy is
where the equipment is placed on your body.  It is important to keep it
at the center of buoyancy with the amount of weight corresponding to
one's body position as they travel through the water.

o Equipment
" Mask  Must be comfortable
" Snorkel  Mandatory for surface swims
" Fins
1. Type 1 Closed Heel (for both SCUBA and Snorkeling)
2. Type 2 Open Heel (best for SCUBA)
o BCD  (Buoyancy Control Device)
o Regulators  Most Imp. Characteristic ease of breathing
 
 
 
 

" 3 States of Buoyancy
1. Positive - If an object displaces an amount of water weighing more than its own weight
2. Neutral - If an object displaces an amount of water weighing equal to its own weight
3. Negative - If an object displaces an amount of water weighing less than its own weight
"
" Because of the increased density of salt water object float better in salt water than they do in fresh water.