Navy Diving Manual Rev 6 Chapter 2 Underwater Physics

Front 1

What is standard cubic feet?

Back 1

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.

Front 2

What are the two general classifications of energy?

Back 2

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.

Front 3

What is refraction and what causes it?

Back 3

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.

Front 4

Refraction causes objects to appear how?

Back 4

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.

Front 5

What happens to light as it travels to depth in clear water?

Back 5

Colors are filtered out starting with Red, Orange, Yellow, Green, Blue – ROYGB

Front 6

Does sound travel faster or slower in water and how does it affect a diver?

Back 6

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.

Front 7

A neoprene wet suit is an effective barrier to sound above what Hz?

Back 7

1,000 Hz

Front 8

When using a diver-held pinger system, divers are advised to wear what for protection?

Back 8

¼” neoprene hood for ear protection.

Front 9

When expecting an underwater explosion, what should a diver do?

Back 9

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.

Front 10

What are the three ways heat is transmitted from one place to another and define each?

Back 10

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.

Front 11

Which method of heat transfer is the most significant means of transmitting heat?

Back 11

Conduction.

Front 12

Which gas is an excellent heat conductor?

Back 12

Helium.

Front 13

Below what water temperature does a diver loose heat faster than he can replace it?

Back 13

70 deg F

Front 14

What effects does low body temperature have on a diver?

Back 14

He cannot work efficiently or think clearly, and is more susceptible to decompression sickness.

Front 15

What is pressure?

Back 15

A force acting upon a particular area of matter measured in pounds per square inch (PSI).

Front 16

What is atmospheric pressure?

Back 16

The pressure that surrounds us at sea level – 14.7 psi or 1 ATA.

Front 17

What is absolute pressure?

Back 17

The total pressure (atmospheric + gauge or hydrostatic pressure) being exerted on a particular area of matter measured in pounds per square inch absolute (PSIA).

Front 18

What is gauge pressure?

Back 18

The difference between atmospheric pressure and the pressure being measured.

Front 19

What is hydrostatic pressure?

Back 19

The weight of the water pushing down at any given depth.

Front 20

What is Archimedes principle?

Back 20

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.

Front 21

How can the buoyancy of an object be determined?

Back 21

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.

Front 22

How much does a cubic foot of fresh water weigh?

Back 22

62.4 lbs

Front 23

How much does a cubic foot of salt water weigh?

Back 23

64 lbs

Front 24

Are objects more buoyant in salt water or fresh water?

Back 24

Salt

Front 25

Divers usually seek a condition of what kind of buoyancy?

Back 25

Neutral or slightly negative.

Front 26

For most purposes and computations, air may be assumed to be composed of what types and % of gases?

Back 26

21% Oxygen and 79% Nitrogen.

Front 27

What is Nitrogen Narcosis?

Back 27

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.

Front 28

What are the disadvantages to using Helium in place of Nitrogen in diving?

Back 28

Distortion of speech (Donald Duck effect), its high thermal conductivity which can cause rapid loss of body and respiratory heat.

Front 29

For divers, what are the two major concerns with carbon dioxide?

Back 29

The control of the quantity in the breathing supply and the removal of the exhaust after breathing.

Front 30

How does Carbon Monoxide affect the body?

Back 30

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.

Front 31

What is the kinetic theory of gases?

Back 31

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.

Front 32

Gases are subject to what three closely interrelated factors?

Back 32

Temperature, pressure, and volume.

Front 33

What is Boyle’s Law?

Back 33

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.

Front 34

How does Boyle’s Law relate to diving?

Back 34

This law relates to diving through squeezes, pulmonary over inflation syndrome, air consumption and minimum manifold pressure.

Front 35

What is Charles’/Gay-Lussac’s Law?

Back 35

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.

Front 36

What is the General Gas Law?

Back 36

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.

Front 37

What is Dalton’s Law?

Back 37

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.

Front 38

What is Partial Pressure?

Back 38

In a gas mixture, it is the portion of the total pressure contributed by a single gas.

Front 39

What is Henry’s Law?

Back 39

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.

Front 40

Which gas law explains why as a diver goes deeper more gas dissolves in his tissues?

Back 40

Henry’s Law

Front 41

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?

Back 41

Henry’s Law

Front 42

Explain the difference between gauge pressure and absolute pressure.

Back 42

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.

Front 43

The amount of nitrogen absorbed in the body depends on what factors?

Back 43

Depth and time at depth.

Front 44

What are the factors that result in the pressure acting on a diver under the sea.

Back 44

The weight of the water and the weight of the atmosphere above the water.

Front 45

Explain how Gay-Lussac’s Law relates to diving

Back 45

This law relates to diving through charging, air in storage, and recompression chambers.

Front 46

Explain how Dalton’s law relates to diving

Back 46

This law relates to diving through gas toxicity at depth and the decompression tables.

Front 47

Explain how Henry’s Law relates to diving

Back 47

This law relates to diving through gas absorption at depth and the amount of time at depth.

Front 48

Define pressure gradient as it applies to decompression theory?

Back 48

The pressure gradient is the difference between the gas tension in a liquid and the partial pressure of a gas outside the liquid.

Front 49

What two (physics) conditions greatly affect the quanity of gas absorbed by a liquid?

Back 49

Temperature and pressure.

Front 50

What is Surface Level Equivalent Value (SEL)?

Back 50

?

Front 51

Generally, how much larger do underwater objects appear?

Back 51

30%

Front 52

What parts of the body are most vulnerable during an explosion?

Back 52

Head, lungs, and intestines

Front 53

What is one atmosphere in PSI and depth?

Back 53

14.7 psi, 33 fsw

Front 54

The affinity of carbon monoxide for hemoglobin is approximately _______ times that of oxygen.

Back 54

200

Front 55

Gases are subject to what three closely interrelated factors?

Back 55

1. Temperature
2. Pressure
3. Volume