Physics Flashcards
What are the terms for the weight of water and the weight of the atmosphere over the water?
Water - Hydrostatic Pressure
Atmosphere - Atmospheric Pressure
What is the weight of the atmosphere at sea level?
14.7 psi
How do you calculate Hydrostatic Pressure?
Depth in Feet of Saltwater (fsw)
(fsw) x .445 = psig
Example: What is the hydrostatic pressure for 33 fsw?
33 x .445 = 14.68 (ROUND UP) = 15 psig
How do you calculate absolute pressure?
Depth to ATA:
D + 33 / 33 = ATA
Example: 60’ + 33 / 33 = 2.81 ata (round up from the hundredths)
PSIG to ATA:
psig + 14.7 / 14.7 = ATA
Example: 25 + 14.7 / 14.7 = 2.70 ata
What is the definition of absolute pressure (ata)?
The total pressure being exerted (i.e. gauge plus atmospheric pressure)
What gas law relates to buoyancy?
Archimedes Principle
What natural factors affect a diver’s buoyancy?
- Air in Lungs
- Bone Structure
- Body Fat
- Leanness
What are the factors that a diver can change to adjust buoyancy?
- Add or remove weight
- Put air in buoyancy compensator/life vest
- Put air in drysuit
- Put air in lungs
- Vary thickness of wetsuit
What equals the buoyant force?
Displaced liquid weight minus submerged body weight
Example: Object Displaces 20 lbs Object Weighs -10 lbs \_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_ Positive 10 lbs
Object Displaces 20 lbs
Object Weighs -30 lbs
___________________
Negative -10 lbs
What is the weight of fresh water and seawater?
Seawater Water: 64 lbs/cubic foot
Fresh Water: 62.4 lbs/cubic foot
What is the definition of Partial Pressure?
In a mixture of gases, each gas contributes to the total pressure of the mixture. This contribution is the partial pressure of the mixture. This contribution is the partial pressure. The partial pressure is the pressure the gas if the gas were in the same volume and temperature by itself.
What is the only gas the body can actually use?
Oxygen
What % of oxygen in air?
21%
What % of nitrogen in air?
79%
What type of gas is nitrogen and what are the properties?
Nitrogen is an inert gas, a gas that the body doesn’t metabolize, that dissolves into the body’s tissues. It is used to dilute O2. (basically a carrier for O2)
What is nitrogen narcosis?
A disorder resulting from anesthetic properties of nitrogen breathed under pressure (usually deeper than 100 fsw)
What produces Carbon Monoxide (CO)?
Incomplete Combustion of Fuels
What produces Carbon Dioxide (CO2)?
By-product of respiration or metabolized O2 in the body
*when breathed at high pp or high concentrations, CO2 can be extremely toxic
How does Boyle’s Law relate to diving?
SPAM S - squeezes P - pulmonary over inflation syndromes (POIS) A - air consumption M - minimum manifold pressure (MMP)
What is minimum manifold pressure?
The supply pressure that will ensure that the gas supply will be delivered at a sufficient pressure to overcome the ambient seawater pressure and allow the equipment to supply the required amount of air to ventilate the rig being used.
How does Charles/Gay Lussac’s Law relate to diving?
CAR
C - charging
A - air and stowage
R - recompression chamber ops
What gas law is the law of partial pressure?
Dalton’s Law
How do you figure the partial pressure (pp) of a gas at a given depth?
ATA x gas % = pp
* gas percentages must be expressed as their decimal equivalent for the equation (21% = .21)
Example: 60' x 21%O2 = ppO2 2.81 x 21%O2 = ppO2 2.81 x .21 = ppO2 2.81 x .21 = .59 ppO2 at 60'
How does Dalton’s Law relate to diving?
Gas toxicity at depth -
- O2 Toxicity
- Nitrogen Narcosis
