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Terms in this set (43)
Equation por pressure
pressure is force acting on a unit area. Pressure = force/ area = F/A
what's atmospheric pressure
the pressure exerted by the earth's atmosphere
What's the atmosphere pressure at sea level?
14.7 psi or 1 atm (atmosphere).
What's hydrostatic pressure?
pressure due to the weight of the water . The deeper the dive, the greater the weight of the water, the greater the hydrostatic pressure
hydrostatic pressure reached on atm at..... feet in seawater
33 feet, and it increases 1 atm every additional 33 ft
hydrostatic pressure reached on atm at..... feet in freshwater
What's absolute pressure?
The sum of atmospheric pressure and hydrostatic pressure
what units are used to describe absolute pressure?
psi( pounds per square inch)
fswa (feet of seawater absolute
ffwa (feed of freshwater absolute)
mmHg (millimeters of mercury absolute
What's gauge pressure?
The difference between atmospheric pressure and the pressure being measured
what terms are used to express gauge pressure?
PSIG (pound per square inch gauge)
What's partial pressure?
The total pressure of a picture of gases is equal to the partial pressure of each gas in the mixture
What's the formula of density
Weight per unit volume = W/V.
As depth increases, the density of the breathing gas increases and thus it becomes heavier per unit volume
What's the density of FW and SW?
FW: 62.4 LBS per cubic foot
SW: 64 Lbs per cubic foot
that's why FW floats on top of SW, and why a diver can float easier in SW.
What's the difference between the english and the international system?
English system: pound (lb); foot (ft); sec (s); Fahrenheit or Rankine
international: kilogram (kg); meter (m); sec (s); Celcius or Kelvin
how many inches in a meter?
how many feet in a meteR?
how much is 1 kg in pounds?
Temperature must be converted to absolute when the gas laws are used?
What does that mean?
that temperature has to be converted to Rankine (R) +-460 or Kelvin (K)+-273 with an absolute zero.
What's the Archimede's principle?
Any object wholly or partly immersed in an fluid is buoyed up by a force equal to the weight of the fluid displaced by the object
What happens when buoyancy is positive, negative and neutral?
the object floats,
What is nitrogen narcosis? How do you know you have that?
As the partial pressure of N2 increases with depth, it produces and intoxicated state, nitrogen narcosis (also known as "inert gas narcosis") that is characterized by loss of judgment and disorientation.
used in diving
does not causes problems associated with nitrogen narcosis
lower density that nitrogen that reduces breathing resistance
disadvantageS: induces heat loss due to its high thermal conductivity
What's the by-product of metabolism?
what does it do to the body when it accumulates?
carbon dioxide, can cause unconsciousness and death.
Interfere's with the blood ability to carry oxygen
Can argon be inhaled?
no because it has narcotic properties
how's neon different from helium?
it causes less voice distortion and has lower thermal conductivity
how is hydrogen (H2) different to all other gases?
what's it disadvantage ?
hydrogen is readily available and produces less breathing resistance at depth than other gases.
it's major disadvantage is that is explosive
What does the gas laws say?
that gases are subject to 3 interrelated factors:
if one changes; all change.
What does the boyle's law say?
For any gas at a constant temperature, the volume of the gas will vary inversely with the pressure
WHat's boyle's equation?
P1: initial pressure surface absolute
V1: initial volume in cubic feet (ft^3)
P2: final pressure absolute
V2: final volume in cubic feet (ft^3)
What does Charles'/Gay-Lussac's Law mean?
For any gas at a constant pressure, the volume of the gas will vary directly with the absolute temperature.
for any gas at a constant volume, the pressure of the gas will vary directly with the absolute temperature
What's charles' equation?
V1/V2 = T1/T2
temperature: Has to be in rankine
Volume: has to be in cubic feet
What's gay-lussac's equation?
Pressure: PSI -> if you have the pressure in PSIG add 14.7 psia.
iF YOU HAVE the pressure in psia, subtract 14.7 to get PSIG = gauge pressure.
What does the dalton's law say?
The total pressure exerted by a mixture of gases is equal tot he sum of the pressures of each of the different gases making up the mixture, with each gas acting as if it alone was present and occupied the total volume.
What's dalton's law equation?
Pt=PP1 + PP2 + PP3, etc
What equation do you use to determine the partial pressure of a gas mixture?
Px = Gas % (decimal) x Pt
how do you convert psi to atmosphere?
X psi x 1 atm / 14.7 psi = X atm
Why is Dalton's law important to divers?
A diver breathing from a tank containing a gas, or contaminate, which is easily tolerated at the surface may experience problems as the partial pressure increases with depth.
What's Henry's Law?
The amount of any given gas that will dissolve in a liquid at a given temperature is proportional to the partial pressure of that gas in equilibrium with the liquid and the solubility coefficient of the gas in the particular liquid.
In other words: if one unit of gas is dissolved at one atm, then two units will be dissolved at 2 atm, 3 at 3 atm, etc
What's henry's equation?
(VG/VL) = (constant) P1
VG= volume of gas dissolved at STPD (Standard temperature pressure dry)
VL= Volume of the liquid
(constant) = solubility coefficient at specified temperatures
P1=partial pressure of that gas above the liquid
What's the pressure gradient?
The difference between the gas tension and the partial pressure outside the liquid is called the pressure gradient; it gives an indication of the net rate the gas tends to enter or leave the solution.
When the pressure gradient is high (low tension & high partial pressure), the rate of absorption into the liquid is high
How does henry's law apply to divers?
The deeper one dives, the greater the pressure, the higher the total pressure of the breathing gas, and the more gas molecules are absorbed into tissues toward the equilibrium of saturation.
As the diver ascends, the pressure gradient reverses and the gas molecules begin to leave the diver's tissues; If the diver's ascent is not controlled, gas bubbles may form producing decompression sickness
General Gas Law (ideal gas law)
The general gas law is a combination of charles and boyles laws. It is used to predict the behavior of a given quantity of gas when changes may be expected in any or all of the variables (pressure, temp, volume)
What's the general gas law equation?
V1)/T1 = (P2
all of these have to be in absolute numbers
how do you convert FSW to PSIA
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