NAUI Diving Physics & Physiology 3

Question 1

What is the partial pressure of nitrogen in air (78% N2) at a depth of 99 feet (4 ATA)?

Accepted Answer

3.12 ATA

Answer

Dalton's Law: partial pressure = fraction × total pressure, so 0.78 × 4 ATA = 3.12 ATA of nitrogen.

Question 2

Decompression sickness (DCS) Type II involves which body systems, making it more serious than Type I?

Accepted Answer

Neurological and cardiopulmonary systems

Answer

Type II DCS affects the spinal cord, brain, and lungs (chokes), and is considered a medical emergency requiring immediate recompression.

Question 3

A diver ascends too quickly after a deep dive. Nitrogen bubbles form in the tissues. What physical law best describes why bubbles form during ascent?

Accepted Answer

Henry's Law — gas dissolving from solution as pressure drops

Answer

Henry's Law states that gas dissolved in liquid will come out of solution when pressure decreases, which is why rapid ascent causes nitrogen bubble formation.

Question 4

Sound travels approximately how much faster in water than in air?

Accepted Answer

Approximately 4 times faster

Answer

Sound travels at about 1,500 m/s in water versus approximately 340 m/s in air, making it roughly 4 times faster underwater.

Question 5

What physiological effect does cold water have on a diver's susceptibility to nitrogen narcosis?

Accepted Answer

Cold water increases narcosis susceptibility

Answer

Cold water, along with anxiety and exertion, increases a diver's susceptibility to nitrogen narcosis, lowering the effective depth threshold.

(NAUI) National Association of Underwater Instructors Certification Practice Test

(NAUI) National Association of Underwater Instructors Certification Practice Test

NAUI Diving Physics & Physiology 3