PADI OPEN WATER CHAPTER 1 QUESTIONS WITH CORRECT ANSWERS GRADED TO PASS

Positive Buoyancy - The tendency of an object to float or rise in a fluid because the object weighs less than the fluid it displaces Neutral Buoyancy - A condition in which an object's mass equals the mass it displaces in a surrounding medium. The object neither sinks nor floats. Negative Buoyancy - The tendency of an object to sink in a fluid because the object weighs more than the fluid it displaces What equipment do you use to control your buoyancy - BCD (buoyancy control device) & lead weights and also your lungs by breathing out (sink) and in (float) Salt water weighs more than fresh making you.. - more buoyant Why do you usually only feel changes of pressure in your body air spaces - Your body is primarily liquid, which is incompressible and distributes pressure equally throughout the body. Why are pressure changes while ascending or descending underwater much more substantial than pressure changes when doing the same in air - Water is much denser and heavier than air, pressure changes much more significantly for a given distance ascent or descent. Air pressure at sea level is - Standard Atmospheric Pressure 1 ata or 1 bar How many ata/bar do you add for every ten meters you descend under water - 1 ata/bar for each 10m/33ft you descend 10m/33ft 2 bar/ata 20m/66ft 3 bar/ata 30m/99ft 4 bar/ata What is the relationship between air volume and density - as pressure increases volume decreases: at 10m/33ft you have 1/2 volume (2bar) at 20m/66ft you have 1/3 volume (3bar) at 30m/99ft you have 1/4 volume (4bar) what do you do to maintain air volume as you descend? - you need to add air to the space to keep up with the volume reduction (equalization) if you added air to a space to maintain its volume while under pressure what happens to that air as the pressure decreases - as you ascend - the air expands what two air spaces should concern you as a diver - ears & sinuses what is squeeze - a pressure imbalance in which pressure outside an air space exceeds pressure inside an air space resulting in pain or discomfort (ears, sinuses, lungs, teeth can squeeze) how can you avoid discomfort from squeeze - add air to the space during descent (equalization) lungs automatically equalize as you... - breathe! three ways to equalize during descent - 1. pinch nose and gently blow 2. swallow and wiggle jaw side to side 3. swallow, wiggle jaw and blow with nose pinched how often should you equalize during descent - every meter/few feet before you feel any discomfort what can happen if you attempt a forceful equalization or extended equalization - ruptured ear drum what should you do if you feel discomfort - ascend until the discomfort eases, equalize and continue a slow descent equalizing more frequently what if you cannot equalize - do not dive how do you equalize your mask - blow out through your nose what can happen if you hold your breath while ascending - the air in your lungs will expand in volume and possibly cause lung over expansion (NEVER HOLD YOUR BREATH) what is the most important rule of scuba diving - breathe continuously and never, never hold your breath when regulator is out of your mouth, what should you do - blow bubbles what is a reverse block - pain and discomfort caused by expanding air trapped inside an air space during ascent (ears, sinuses) what should you do if you feel discomfort during ascent due to air expansion in the ears, sinuses, stomach, intestines or teeth - stop your ascent, descend a meter/few feet and give the trapped air time to work its way out how does increasing depth affect how long your air supply lasts - at 20m/66ft (3 bar/ata) for each breath you need 3 times the number of air molecules to fill your lungs to the same volume. so your air supply lasts 1/3 as long as it does on the surface What happens to air density as you descend - Air becomes more dense and dense air is harder to inhale and exhale - don't overexert yourself and take deep slow breaths. should you ever be out of breath while you are diving? - No, relax and breath normally why do you need a mask - light behaves differently in water than in air and our eyes focus according to how light behaves in air mask features - tempered glass comfortable skirt nose or finger pockets low-profile adjustable strap wide field of vision optional purge valve see quiz page 32 why do you need a snorkel - let's you rest or swim with your face in the water without wasting cylinder air and if there is surface chop(waves), water can get in your mouth and if you run low on air away from the boat or shore it makes it easier to swim what 3 features does an easy breathing snorkel have - a large bore not excessively long designed with smooth rounded bends quiz pg 35 why does a diver need fins - provide a large surface area, so leg muscles can move through the water what are the two basic fin styles - adjustable strap and full foot what blade design features may enhance performance - ribs - add rigidity and act as vertical stabilizer vents - reduce resistance and increase efficiency channels - increase efficiency by guiding water over fin quiz pg 37