PADI Physics and Gas Laws 3 — Questions and Answers
Question 1: A flexible balloon contains 6 liters of air at the surface. What volume will it have at 66 feet (20 m, 3 ATA)?
- 2 liters (Correct answer)
- 3 liters
- 4 liters
- 18 liters
Correct answer: 2 liters
Boyle's Law: V2 = (P1 × V1) / P2 = (1 × 6) / 3 = 2 liters.
Question 2: The term 'partial pressure' refers to:
- The pressure contributed by a single gas in a mixture (Correct answer)
- The pressure at the bottom of a partial dive
- Half the total ambient pressure
- The pressure in a partially filled tank
Correct answer: The pressure contributed by a single gas in a mixture
Dalton's Law defines partial pressure as each gas component's individual contribution to total pressure.
Question 3: At what partial pressure of oxygen does acute CNS oxygen toxicity become a significant risk during diving?
- Above 1.6 ATA (Correct answer)
- Above 0.21 ATA
- Above 1.0 ATA
- Above 2.5 ATA
Correct answer: Above 1.6 ATA
PADI guidelines set 1.6 ATA ppO2 as the maximum limit for recreational diving to avoid CNS oxygen toxicity.
Question 4: Light refraction underwater makes objects appear:
- Closer and larger than they actually are (Correct answer)
- Farther and smaller than they actually are
- The same size but shifted in position
- Blurry and indistinct regardless of distance
Correct answer: Closer and larger than they actually are
Due to refraction at the mask lens interface, objects underwater appear about 25% closer and 33% larger than actual.
Question 5: Sound travels underwater approximately how much faster than in air?
- 4 times faster (Correct answer)
- 2 times faster
- The same speed
- 10 times faster
Correct answer: 4 times faster
Sound travels roughly 1,500 m/s in water compared to about 340 m/s in air — approximately 4 times faster.
Question 6: The combined gas law incorporates which three individual gas laws?
- Boyle's, Charles's, and Gay-Lussac's (Correct answer)
- Boyle's, Dalton's, and Henry's
- Charles's, Dalton's, and Henry's
- Boyle's, Henry's, and Gay-Lussac's
Correct answer: Boyle's, Charles's, and Gay-Lussac's
The combined gas law merges Boyle's (pressure-volume), Charles's (volume-temperature), and Gay-Lussac's (pressure-temperature) laws.
Question 7: Which factor does NOT affect the rate of nitrogen absorption in a diver's tissues according to diving physics?
- The color of the diver's wetsuit (Correct answer)
- Depth (partial pressure of nitrogen)
- Duration of the dive
- Blood circulation to tissues
Correct answer: The color of the diver's wetsuit
Wetsuit color has no effect on gas absorption; depth, time, and circulation all influence nitrogen uptake.
PADI Physics and Gas Laws 3
A flexible balloon contains 6 liters of air at the surface.
What volume will it have at 66 feet (20 m, 3 ATA)?