Glossary of Physics Mod 001

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List 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 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.
State Archimede’s Principle.
Any object wholly or partially submerged in a liquid will be buoyed up by a force equal to the weight of the liquid displaced by the object.
4. Is it easier for an object to float in sea water or fresh water? Why?
Sea water, because it has a greater density (has more weight) than fresh water.
Name a specific diving related problem that is directly related to Boyle’s Law.
AGE (POIS), squeezes.
6. Which gas law explains why as a diver goes deeper more gas dissolves in his tissues?
Henry’s Law.
7. State Charles’ / Gay-Lussac’s Law.
For any gas at a constant volume, the pressure of the gas will vary directly as the absolute temperature
What happens to light as it travels to depth in clear water?
Red light is filtered out followed by orange, yellow, green and blue.
The amount of nitrogen absorbed in the body depends on what factors
Depth and time at depth.
Define residual nitrogen and Residual Nitrogen Time (RNT).
Residual Nitrogen is that gas that is still dissolved in a diver’s tissues after surfacing. Residual Nitrogen Time is the time in minutes, which must be added to the bottom time of the repetitive dive to compensate for the nitrogen still in solution in a diver’s tissues from a previous dive.
What is the rate of ascent when surfacing from a dive?
30 FPM. Minor variations in rate of travel between 20 and 40 FPM are acceptable.
Up to what altitude may normal air decompression tables be used?
Up to 300 feet of altitude for all dives. Up to 1000 feet of altitude for all dives less than 145 FSW.
What must be considered if you are planning to dive within a 12 hour period?
Residual Nitrogen Time.
Who can provide altitude tables above 10,000 feet when authorization is granted?
How can you ensure that the selected decompression schedule is always conservative
Always select the schedule depth equal to or next greater than the maximum depth of the dive and select the schedule bottom time equal to or next longer than the bottom time of the dive.
What is a repetitive dive?
dive conducted more than10 minutes and within 12 hours of a previous dive.
State the RNT exception rule.
When a repetitive dive is made to the same or greater depth than the previous dive, the residual nitrogen time may be longer than the bottom time of the previous dive, in this case add the actual bottom time of the previous dive to the bottom time of the repetitive dive to obtain ESDBT.
What is the disadvantage of nitrogen when used in diving at deep depths?
High partial pressure will cause nitrogen narcosis.
7. 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.
Figure the partial pressure of oxygen and nitrogen at:
33’ .42 ppO2 1.58 ppN2

66’ .63 ppO2 2.37 ppN2

172’ 1.30 ppO2 4.90 ppN2

220’ 1.60 ppO2 6.05 ppN2
If a diver is ascending too fast, what should be done?
Stop the ascent, allow the watches to catch up and then continue ascent.
When a diver is extremely cold, what course of action can be taken regarding decompression?
Select the next longer decompression schedule.
How can the buoyancy of a submerged object be established?
Weight of the liquid displaced minus the weight of the object
Define bottom Time.
The total elapsed time from when the divers leave the surface to the time they begin their ascent from the bottom. This time is measured in minutes (rounded up to the next whole minute).
What is TDT and how is it figured?
Total Decompression Time. Time divers leave the bottom until they reach the surface after completing all their decompression requirements.

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