Physics Flashcards
The bending of light as light goes from one medium to another is called what?
The bending of light as light goes from one medium to another is called refraction.
Do objects in water appear closer, or farther away than they really are and by how far?
Objects in water appear closer, due to refraction.
Objects appear 25% closer.
What is the magnification of an object underwater?
The magnification of an object underwater is 33%.
So if you think you see a 4m long shark, it’s really 3m long.
Do objects look 25% closer underwater or 33% closer underwater?
Objects look 25% closer and 33% larger underwater.
What is visual reversal?
Visual reversal is when things appear further away than they really are.
Turbidity is the most important factor affecting visual reversal.
Do objects in cloudy water look further away or closer than they really are?
Objects in cloudy water look further away due to visual reversal.
What is gauge pressure?
Gauge pressure is the pressure of the water without the 1 atmosphere of surface presure.
10 m = 1 atmosphere gauge.
Think about how your guages (computer) depth “guage” reads presure.
What is absolute pressure?
Absolute pressure is 1 atmosphere at sea level + 1 x the hydrostatic pressure of the water column surrounding you.
10 m = 2 atmospheres absolute = 2 ATA.
What does the abbreviation ATA mean?
The abbreviation ATA means Atmospheres Absolute.
What is ambient pressure?
Ambient pressure is the surrounding pressure
= ambient or absolute pressure.
Two of these are the same.
Ambient Pressure; Gauge Pressure; Absolute Pressure.
Which ones?
Two of these are the same.
Ambient = Absolute.
Remember, they both begin with the letter A.
The Greek mathematician Archimedes determined that ‘An object wholly or partially immersed in a fluid is buoyed up by a force equal to the weight of the fluid displaced by the object’.
An object that weighs less than the water it displaces will do what?
An object that weighs less than the water it displaces will float and is positively buoyant.
It’s buoyancy is expressed as a positive number, such as being 2 kgs positive. An object that weighs exactly the same as the water it displaces and neither sinks nor floats is neutrally buoyant.
Because a divers lung volume must remain constant regardless of the depth at which he/she breaths, would the density of the air in the divers lungs change as he/she changes depth?
The density of the air in the divers lungs won’t change at depth.
When we breathe, we must breathe a “full” breath regardless of the pressure surrounding us. And, to be able to breathe, the external pressure must be equal to the air we are breathing.
The effect is caused by the difference between the surface air pressure and the water pressure surrounding your chest.
Which law dictates this?
“If the pressure increases (gets more), the more gas will be dissolved (go into) the liquid (on gassing) and If pressure (depth) decreases on a liquid, dissolved gases come out of solution (off gassing)”.
Henry’s Law dictates that,
“If the pressure increases (gets more), the more gas will be dissolved (go into) the liquid (on gassing) and If pressure (depth) decreases on a liquid, dissolved gases come out of solution (off gassing)”.
Which law deals with the relationship between pressure and volume?
It states that for a fixed quantity of gas (at constant temperature) and the volume of the gas is inversely proportional to the pressure of the gas.
Boyles Law deals with the relationship between pressure and volume.
It states that for a fixed quantity of gas (at constant temperature) and the volume of the gas is inversely proportional to the pressure of the gas.
Which law says that at 10metres the pressure is 2 ATA?
Boyle’s Law says that at 10metres the pressure is 2 ATA.
What is gas tension?
Gas tension is the pressure exerted by gasses dissolved in a liquid.
The more gas that is dissolved in a liquid, the greater the gas tension.
What is supersaturation?
Supersaturation is when gas is dissolved in a liquid at equilibrium, then surface pressure is reduced, (ascent) gas tension becomes higher than the surface tension, and the gas comes out of solution.
What is conduction?
Conduction is the transmission of heat by direct contact.
What is the transmission of heat energy by fluids called?
The transmission of heat energy by fluids called convection.
What are the three ways heat is transmitted?
The three ways heat is transmitted are radiation, convection, and conduction.
Which of the three ways heat is transmitted is most important to diving?
Radiation, convection or conduction.
The most important way heat is transmitted in diving is conduction.
Radiation and convection are relatively unimportant to divers.
What is conducted 20 times faster in water than in air?
Heat is conducted 20 times faster in water than in air.
What travels 4 times faster in water, than in air?
Sound travels 4 times faster in water, than in air.
It is denser than air helping sound travel and always sounds as if it is coming from above you (overhead).
How many metres of seawater adds one atmosphere of pressure?
10metres of seawater adds one atmosphere of pressure.
0m = 1ATM
10m = 2ATA
20m =3ATA
How many meters of fresh water adds one atmosphere of pressure?
10.3meters of fresh water adds one atmosphere of pressure?
0m = 1ATM
- 3m = 2ATA
- 6m =3ATA
Diving 10meters adds one atmosphere of pressure in which body of water?
Seawater or fresh water.
Diving 10meters adds one atmosphere of pressure in seawater.
Why is water able to conduct heat more efficiently than air?
Water able to conduct heat more efficiently than air because water is more dense than air.
1lt of fresh water = how many kg?
1lt of fresh water = 1kg
1 lt of salt water = how many kg?
1lt of salt water = 1.03kg
If a diver’s air consumption rate is 2 bar/min at the surface.
What will the diver’s air consumption be at 30m, and what will the density be?
If a diver’s air consumption rate is 2 bar/min at the surface.
The diver’s air consumption be at 30m will be 3atm + 1 atm at the surface = 4atm (therefore 4 times as dense).
4 x 2 bar/min. = 8 bar/min at 30m.
If you have air mix of 1% CO2, 79% N2 and 20% O2, what will the Pp (partial pressure) of N2 at 40metres?
If you have an air mix of 1% CO2, 79% N2 and 20% O2, the Pp (partial pressure) of N2 at 40metres will be Pp3.95N2.
40m = 5ATA
5 x Pp0.79N2 = Pp3.95N2
If an air mix has 0.5% carbon monoxide in it, breathing it at 40metres would be the equivalent of breathing what percent at the surface?
If an air mix has 0.5% carbon monoxide in it, breathing it at 40metres would be the equivalent of breathing 2.5% carbon monoxide at the surface.
40m = 5ATA
5 x 0.5% = 2.5%
Why do divers have trouble determining the origin of sound underwater?
Divers have trouble determining the origin of sound underwater because there is an insuficient delay between the sound striking each ear.
If you take a container filled with air up from depth, what will happen to the volume?
If you take a container filled with air up from depth, the volume will increase (get bigger) and the air will become less dense (less pressure).
Whose law is associated to decompression sickness (DCS), the build up of nitrogen bubbles in the body?
Henry’s Law is associated to decompression sickness (DCS), the build up of nitrogen bubbles in the body?
If you shake a Coca-Cola bottle, you’re building up pressure inside the bottle, forcing gas into the cola (solution) .
When you slowly open the bottle you decrease the pressure (like when you ascend) and all the gas comes out of the cola (solution).
If you take a container filled with air down to depth, the volume will do what?
If you take a container filled with air down to depth, the volume will decrease (get less).
When taken down You divide (/) the volume by the atmospheric presure.
As the pressure surrounding an object increases (gets more) the volume will decrease (get less) and the density will increase (get more)
Arrange the list of colors by the order that they disappear as you descend:
Yellow
Blue
Red
Violet
Green
Orange
The list of colors by the order that they disappear as you descend:
Red
Orange
Yellow
Green
Blue
Violet
What is Dalton’s Law?
Dalton’s Law is the relationship of pressure & partial pressure of gases such as Oxygen, Helium, Nitrogen and Carbon Dioxide.
The sum of gases will always equal a whole (100%)
As the pressure increases, the partial pressure (not the percentage) will increase.
How many times more is the air that a diver breathes from a scuba cylinder at 50metres of seawater as the air breathed from the same cylinder at the surface?
The air that a diver breathes from a scuba cylinder at 50metres of seawater is 6 times as dense as the air breathed from the same cylinder at the surface.
50m = 5 ATA+1 ATM from the surface = 6 ATA so 6 times as dense.
If it takes a diver 40minutes to breathe all the air from a scuba tank at the 20metres approximately how long will the air in that tank last at 30 metres?
If it takes a diver 40minutes to breathe all the air from a scuba tank at the 20metres, it would take approximately 30minutes for the air in that tank last at 30metres?
20metres = 3ATM
3ATM x 40minutes = 120minutes (surface time)
30metres = 4ATM
4ATM / 120 minutes = 30 minutes
- If you’re going up x*
- If you’re going down /*
A balloon is filled with 60litres of air at 30metres in seawater.
What will be the approximate volume of the balloon be, if it is taken to a depth of 90metres?
A balloon is filled with 60litres of air at 30meters in seawater.
The approximate volume of the balloon if it is taken to a depth of 90metres, will be 24litres.
30metres = 4ATM
60litres x 4ATM = 240litres (surface volume)
90metres = 10ATM
240litres / 10ATM = 24 litres
A scuba cylinder (non flexible container) is filled to capacity at room temperature.
What would happen to that cylinder if it was taken on an ice dive?
A scuba cylinder (non flexible container) is filled to capacity at room temperature.
The volume of the cylinder would remain unchanged, but the pressure would decrease.
Charles Law.
A scuba cylinder containing 1% carbon dioxide at the surface is taken down to a depth of 30meters.
What is the percentage of carbon dioxide in the cylinder at this depth?
A scuba cylinder containing 1% carbon dioxide at the surface is taken down to a depth of 30meters.
The percentage of carbon dioxide in the cylinder at this depth is 1% because percentage does not change.
Don’t get confused with partial pressure.
Because our bodies tissues cannot hold any more gas pressure at sea level, what is our body is referred to as being?
Because our bodies tissues cannot hold any more gas pressure at sea level, our body is referred to as being saturated.
Approximately how much air must be added to a lifting device to bring a 600 kilogram object to the surface,if the object lies in 30 metres of freshwater?
Approximately how much air must be added to a lifting device to bring a 600 kilogram object to the surface,if the object lies in 30 metres of freshwater?
The answer cannot be determined from the data provided.
You need to know the displacement (upward force).
A 500kilogram anchor that displaces 300 litres of water lies on the bottom in 40 metres of sea water.
What is the minimum amount of water that must be displaced from a lifting device to bring the anchor to the surface?
A 500kilogram anchor that displaces 300 litres of water lies on the bottom in 40 metres of sea water.
The minimum amount of water that must be displaced from a lifting device to bring the anchor to the surface is approximatley 185litres.
500kg = downward force
300litres = each litre of displacement represents 1.03kg/litre of upward force. (1.03 for sea water)
1.03kg x 300litres = 309kg (buoyant force)
500kg - 309kg = 191 kg (downward force)
191kg / 1.03kg = 185.4litres
Remember, the depth doesnt matter because water is not compresable so just, Multiply, Subtract and Divide.
What is Charles’ Law?
Charles’ Law is the relationship of temperature & pressure.
As the temperature increases the volume of a flexible container will increase, but the density (pressure) inside a non-flexible container (scuba cylinder) will increase.
Would the gauge pressure for a given depth in salt water be different in the same depth of fresh water?
The gauge pressure for a given depth in salt water would be greater than the guage pressure in the same depth of fresh water.
10metres (SEA WATER) = 1 BAR
(e.g. 34metres = 3.4BAR gauge pressure)
34metres / 10metres = 3.4
10.3metres (FRESH WATER) = 1 BAR
(e.g. 34metres = 3.3BAR gauge pressure)
34metres / 10.3metres = 3.3
If a diver breathes a complete cylinder of air in 70minutes at the surface, how long would it take to breathe the whole cylinder at 25metres?
If a diver breathes a complete cylinder of air in 70minutes at the surface, it would take the diver 20minutes to breathe the whole cylinder at 25metres?
20minutes.
25m = 3.5ATM
70minutes / 3.5ATM = 20minutes.
