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55 Cards in this Set

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What is standard cubic feet?
The measurement of a gas under pressure to a specific condition. For air, the standard cubic foot is measured at 60 deg F and 14.696.
What are the two general classifications of energy?
Potential energy – a car parked on a hill with its brake on possesses potential energy. Kinetic energy – a car rolling on flat road possesses kinetic energy.
What is refraction and what causes it?
Light passing from an object bending as it passes through the diver’s faceplate and the air in is mask and occurs because light travels faster in air than in water.
Refraction causes objects to appear how?
Closer than they really are. A distant object will appear to be approximately three-quarters of its actual distance, but at greater distances, the effects of refraction may be reversed. It also causes objects to appear to be about 30% larger than they actually are.
What happens to light as it travels to depth in clear water?
Colors are filtered out starting with Red, Orange, Yellow, Green, Blue – ROYGB
Does sound travel faster or slower in water and how does it affect a diver?
It travels farther and faster in the denser medium. Human ears cannot detect the difference in time of arrival of a sound at each ear. Consequently, a diver cannot always locate the direction of a sound source.
A neoprene wet suit is an effective barrier to sound above what Hz?
1,000 Hz
When using a diver-held pinger system, divers are advised to wear what for protection?
¼” neoprene hood for ear protection.
When expecting an underwater explosion, what should a diver do?
Get out of the water and out of range of the blast whenever possible. If the diver must be in the water, it is prudent to limit the pressure he experiences from the explosion to less than 50 psi by positioning himself with feet pointing toward and head directly away from the explosion with head and upper section of the body out of the water or the diver should float on his back with his head out of the water.
What are the three ways heat is transmitted from one place to another and define each?
Conduction, Convection, and Radiation. Conduction is the transmission of heat by direct contact. Convection is the transfer of heat by the movement of heated fluids. Radiation is heat transmission by electromagnetic waves of energy.
Which method of heat transfer is the most significant means of transmitting heat?
Conduction.
Which gas is an excellent heat conductor?
Helium.
Below what water temperature does a diver loose heat faster than he can replace it?
70 deg F
What effects does low body temperature have on a diver?
He cannot work efficiently or think clearly, and is more susceptible to decompression sickness.
What is pressure?
A force acting upon a particular area of matter measured in pounds per square inch (PSI).
What is atmospheric pressure?
The pressure that surrounds us at sea level – 14.7 psi or 1 ATA.
What is absolute pressure?
The total pressure (atmospheric + gauge or hydrostatic pressure) being exerted on a particular area of matter measured in pounds per square inch absolute (PSIA).
What is gauge pressure?
The difference between atmospheric pressure and the pressure being measured.
What is hydrostatic pressure?
The weight of the water pushing down at any given depth.
What is Archimedes principle?
Any object wholly or partly immersed in a fluid is buoyed up by a force equal to the weight of the fluid displaced by the object.
How can the buoyancy of an object be determined?
Subtracting the weight of the submerged object from the weight of the displaced liquid. If the weight of displaced liquid is greater than the weight of the submerged object it will float.
How much does a cubic foot of fresh water weigh?
62.4 lbs
How much does a cubic foot of salt water weigh?
64 lbs
Are objects more buoyant in salt water or fresh water?
Salt
Divers usually seek a condition of what kind of buoyancy?
Neutral or slightly negative.
For most purposes and computations, air may be assumed to be composed of what types and % of gases?
21% Oxygen and 79% Nitrogen.
What is Nitrogen Narcosis?
A disorder resulting from the anesthetic properties of nitrogen breathed under pressure, which can result in a loss of orientation and judgment by the diver.
What are the disadvantages to using Helium in place of Nitrogen in diving?
Distortion of speech (Donald Duck effect), its high thermal conductivity which can cause rapid loss of body and respiratory heat.
For divers, what are the two major concerns with carbon dioxide?
The control of the quantity in the breathing supply and the removal of the exhaust after breathing.
How does Carbon Monoxide affect the body?
It interferes with the blood’s ability to carry the oxygen required for the body to function normally. The affinity of CO for hemoglobin is approximately 210 times that of oxygen and dissociates from the hemoglobin at a much slower rate than oxygen.
What is the kinetic theory of gases?
The basic explanation of the behavior of gases under all variations of temperature and pressure. The kinetic energy of any gas at a given temperature is the same as the kinetic energy of any other gas at the same temperature.
Gases are subject to what three closely interrelated factors?
Temperature, pressure, and volume.
What is Boyle’s Law?
States that at a constant temperature, the absolute pressure and the volume of gas are inversely proportional. As pressure increases the volume decreases and vice-versa.
How does Boyle’s Law relate to diving?
This law relates to diving through squeezes, pulmonary over inflation syndrome, air consumption and minimum manifold pressure.
What is Charles’/Gay-Lussac’s Law?
Describes the physical relationships of temperature upon volume and pressure. At a constant pressure, the volume of a gas is directly proportional to the change in the absolute temperature. If the pressure is constant and the temperature is doubled, the volume will double. If the volume instead of pressure is kept constant (I.E. heating in a rigid container), then the absolute pressure will change in proportion to the absolute temperature.
What is the General Gas Law?
It combines Boyle’s, Charles, and Gay-Lussac’s laws to predict the behavior of a given quantity of gas when any of the factors change.
What is Dalton’s Law?
The law of partial pressures. The total pressure exerted by a mixture of gasses is equal to the 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 is Partial Pressure?
In a gas mixture, it is the portion of the total pressure contributed by a single gas.
What is Henry’s Law?
The law of absorption. The amount of any given gas that will dissolve in a liquid at a given temperature is directly proportional to the partial pressure of that gas.
Which gas law explains why as a diver goes deeper more gas dissolves in his tissues?
Henry’s Law
By controlling our ascent, dissolved gas will be carried to the lungs and exhaled before it accumulates sufficiently to form bubbles in the tissues. Which gas law explains this release?
Henry’s Law
Explain the difference between gauge pressure and absolute pressure.
Gauge pressure is the difference between atmospheric pressure and the pressure being measured, while absolute pressure is the total pressure or gauge pressure plus one atmosphere.
The amount of nitrogen absorbed in the body depends on what factors?
Depth and time at depth.
What are the factors that result in the pressure acting on a diver under the sea.
The weight of the water and the weight of the atmosphere above the water.
Explain how Gay-Lussac’s Law relates to diving
This law relates to diving through charging, air in storage, and recompression chambers.
Explain how Dalton’s law relates to diving
This law relates to diving through gas toxicity at depth and the decompression tables.
Explain how Henry’s Law relates to diving
This law relates to diving through gas absorption at depth and the amount of time at depth.
Define pressure gradient as it applies to decompression theory?
The pressure gradient is the difference between the gas tension in a liquid and the partial pressure of a gas outside the liquid.
What two (physics) conditions greatly affect the quanity of gas absorbed by a liquid?
Temperature and pressure.
What is Surface Level Equivalent Value (SEL)?
?
Generally, how much larger do underwater objects appear?
30%
What parts of the body are most vulnerable during an explosion?
Head, lungs, and intestines
What is one atmosphere in PSI and depth?
14.7 psi, 33 fsw
The affinity of carbon monoxide for hemoglobin is approximately _______ times that of oxygen.
200
Gases are subject to what three closely interrelated factors?
1. Temperature
2. Pressure
3. Volume