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IDC > Physics > Flashcards

Physics Flashcards

1
Q

1 litre of salt water weighs…

A

1.03kg

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2
Q

SW Absolute pressure =

A

Depth/ 10 + 1

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3
Q

1 litre of fresh water weighs?

A

1 kg

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4
Q

SW Ambient pressure =

A

Depth/ 10 + 1

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5
Q

SW Gauge Pressure =

A

Depth/ 10

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6
Q

Daltons Law

A

Percentage (decimal) x pressure = partial pressure

Eg. 0.21 x 2 = 0.42 pp of 02 at 10m

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7
Q

Water has the capacity to ____ light. ____ is the first colour to disappear underwater

A

Refract
Red

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8
Q

Water dissipates body heat faster than air does, because it absorbs heat approximately ___ times faster than air does

A

X20

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9
Q

Light ____ speed and direction (___) when it passes through a substance of one density into a substance of a different density

A

Changes speed and direction (refract)

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10
Q

Due to refraction, underwater objects appeared to be magnified by a factor of ____

A

4/3

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11
Q

Sound travels approximately ___ times faster in water than in air

A

X4

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12
Q

Why does sound travel faster in water

A

Water is more dense

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13
Q

Because sound travels faster underwater it is ____ to determine the direction a sound is coming from

A

Harder

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14
Q

If a diver is in fresh water at 10.3m, what is the ambient pressure

A

2 bar

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15
Q

10.3 of fresh water = __ bar of pressure change

A

1 bar of pressure change

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16
Q

10m of salt water = ___ bar of pressure change

A

1 bar

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17
Q

A diver in seawater at 20m brings a balloon of air to the surface. Assuming the balloon will not burst. It’s volume will be …. what is was at depth

A

X3

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18
Q

Cylinder of air at 20m last you 40 mins. How long would expect the same cylinder to last you at 10m ?

A

60 mins

20m = 1/3 (40mins)
10m = 1/2 (60 mins)
0m = 1 (120mins)

40 x 3 / 2

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19
Q

Prior to a visual inspection, a technician releases all air from a cylinder that started with 205 bar. You would expect the cylinder to
A) cool
B) warm
C) same temp
D) not enough info to answer

A

Pressure decreases
Temp decreases

= cool

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20
Q

Which of the following will increase an objects buoyancy
A) add weight
B) remove weight
C) increase displacement
D) decrease displacement in

A

B + C

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21
Q

If an object is neutrally buoyant in salt water it will ___ in fresh water

A

Sink

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22
Q

Using your lungs to control buoyancy is an example of ____

A

Displacement

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23
Q

What is partial pressure?

A

🐳 Absolute pressure x gas percentage
🐳 Total pressure exerted by a certain gas in a gas mixture
🐳 Related to a solution of gases in a liquid

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24
Q

Breath gas at depth the effect will be ___ than at the surface

A

Greater

Nitrogen Natcosis
CO poisoning

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25
Q

When you raise the pressure of a gas in a liquid the gas ___ the solution until reaching ____

A

Into the solution until reaching saturation

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26
Q

When you reduce the pressure of gas in contact with a liquid ____

A

Bubbles may form, depending on degree of pressure change

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27
Q

A PADI enriched air diver is using EANx30 at 30m. What is the PO2?

A

0.3 x 4 = 1.2 pp02

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28
Q

A container weighs 10,000kg and is neutrally buoyant in salt water. What is the volume of the water it displaces

A

1 litre of salt water = 1.03 kg

Kg -> litres …. kg / 1.03

10,000kg / 1.03 = 9,708 litres

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29
Q

FW Absolute pressure

A

Depth / 10.3 + 1

30
Q

FW Ambient Pressure

A

Depth/ 10.3 + 1

31
Q

FW Gauge pressure

A

Depth / 10.3

32
Q

A 500kg mooring block lies in 29m of salt water. Block displaces 300 litres of water. To move the block off the bottom, what is the minimum amount of water that must be displaced from the lifting device.

A

1 litre of SW = 1.03 kg
500kg = 485 litres

So you need 185 litres

33
Q

200 bar of pressure takes 60 mins to breath at surface. How long would it take at 15m?

A

15m = 2.5
Will breath it x2.5 faster
60 / 2.5 = 24 mins

34
Q

I have a balloon with a vol of 2 litres at 30m. What’s the vol at 20m

A

30m = 1/4
20m = 1/3

2 x 4 / 3 = 2.67

35
Q

Boyles Law

A

0m - 1 bar - 1 litre
10m - 2 bar - 1/2 litre
20m - 3 bar - 1/3 litre
30m - 4 bar - 1/4 litre
40m - 5 bar - 1/5 litre

36
Q

Divers are most affected by what form of heat transmission?

A

Conduction

37
Q

Water conducts heat x___ faster than air

A

x20

38
Q

Underwater objects appear magnified by a factor of ___

A

33%

39
Q

Visual reversal

A

Object appears further away

40
Q

What affects visual reversal

A

Turbidity

41
Q

What form of energy are light waves?

A

Electromagnetic

42
Q

What form of energy are sound waves?

A

mechanical energy

43
Q

The density and elasticity of a medium has what effect upon the transmission of sound?

A

more dense + elastic = faster transfer

44
Q

Sound travels x___ faster in water than in air

A

x4 travels

heat transfer is x20

45
Q

Why do divers have difficulty determining the direction of sound underwater?

A

There is an insufficient delay between the sound striking one ear before the other

46
Q

The specific gravity of pure water?

A

1.0

47
Q

Approximately how much water must be displaced to bring a 500 kilogram object to the surface if the object displaced 300 litres? The object lies in 40 metres of seawater.

A

185 litres

48
Q

An object weighing 350 kilograms and displacing 300 litres is lying in 15 metres of fresh water. If a drum is to be used to lift the object to the surface, how much water must be displaced from the drum?

A

50 litres

49
Q

a 30 litre balloon at 10ata would be what volume at 50m?

A

30litres at 10ata = 90m = 1/10

50m = 1/6

30 x 10 / 6 = 50

50
Q

A balloon is filled with 60 litres of air at 30 metres of seawater. What will be the approximate volume of the balloon if it is taken to a depth 90 metres?

A

24 litres

51
Q

A balloon containing 300 litres of air at 7 metres of seawater is taken to a depth of 26 metres. What will be the exact volume of the balloon upon reaching 26 metres?

A

300 litres @ 7m = 1/1.7
26m @ 1/ 3.6

300x 1.7 / 3.6 = 141.66

52
Q

A scuba cylinder is filled to capacity at the surface. When this cylinder is used at a depth of 30 metres in the sea, the air within the cylinder is four times more dense than it was at the surface. True or False

A

The density of air in the cylinder will not change so False

53
Q

Because a diver’s lung volume must remain constant regardless of the depth at which he breathes, the density of the air in the diver’s lungs does not change even as he changes depth.

A

False

54
Q

The air that a diver breathes from a scuba cylinder at 50 metres of seawater is ______ as dense as the air breathed from the same cylinder at the surface.

A

x6

55
Q

A diver has an air consumption rate of 2 bar per minute at the surface. If all other factors but depth remain unchanged, what will his consumption rate be at 40 metres of seawater?

A

10 bar / min

56
Q

A diver has an air consumption rate of 60 litres per minute at 10 metres of seawater. If all other factors but depth remain unchanged, what will his consumption rate be at 30 metres?

A

120litres/ min

57
Q

A diver has an air consumption rate of 90 litres per minute at 20 metres of seawater. If all factors, but depth remain unchanged, what will his consumption rate be at 60 metres?

A

210 litres/ min

58
Q

A diver has an air consumption rate of 60 litres per minute at 10 metres of seawater. If all other factors but depth remain unchanged, what will his consumption rate be, in bar per minute, at 30 metres?

A

not enough data to give answer. You know its 120l/ min but can’t convert it to bar

59
Q

A balloon is filled with 30 litres of air at room temperature. Describe what would happen to that balloon if it were put into a freezer at a constant ambient pressure.

A

vol would decrease

59
Q
A
60
Q

A scuba cylinder is filled to capacity at room temperature. Describe what would happen to that cylinder if it was taken on an ice dive (water at or near freezing).

A

vol the same. pressure decrease

61
Q

temp and pressure change. For every 1 degree in temp change how much bar change ___?

A

0.6 bar change per degree of temp change

62
Q

A 12 litre scuba cylinder is filled to 200 bar at an ambient temperature of 27° C. If the cylinder is then used in water temperature of 4° C, what would be the approximate cylinder pressure?

A

27 - 4 = 23

23 x 0.6 = 13.8

200 - 14 = 186 bar

63
Q

A gas mixture is comprised of 21% oxygen, 78% nitrogen and 1% carbon dioxide. At a depth of 24 metres, what is the partial pressure of the oxygen?

A

0.21 x 3.4 = 0.7

64
Q

A scuba cylinder is accidentally filled with 1% carbon monoxide. If a diver breathes air from this cylinder at a depth of 30 metres of seawater, approximately what percentage of carbon monoxide will he be breathing?

A

1%

65
Q

Referring to the previous question (a scuba cylinder is accidentally filled with 1% carbon monoxide), it is determined that at the surface the diver inhales 500,000 molecules of carbon monoxide with each breath. Therefore, when breathing the air at 30 metres of seawater (assuming all other factors but depth are unchanged), he would breathe approximately how many molecules?

A

2,000,000

66
Q

Again referring to question 1 (a scuba cylinder is accidentally filled with 1% carbon monoxide), breathing the contaminated air at 30 metres of seawater would have the same effect on the diver as breathing what percentage of carbon monoxide at the surface?

A

4%

67
Q

A glass of water has been placed in a vacuum for several days. It no longer contains any dissolved gas within it. If it is then placed in a pressure pot and pressurized to 2 ata for several days, what will be the gas pressure within the liquid?

A

2 ata

68
Q

If the pressure within the pot in the previous question (A glass of water has been placed in a vacuum for several days. It no longer contains any dissolved gas within it. it is then placed in a pressure pot and pressurized to 2 ata for several days) is increased, the pressure of the gas within the liquid will:

A

increase

69
Q

If a vacuum is created within the pressure pot in question 1 (A glass of water has been placed in a vacuum for several days. It no longer contains any dissolved gas within it. it is then placed in a pressure pot and pressurized to 2 ata for several days), the pressure of the gas within the liquid will:

A

Decrease

70
Q

When breathing at depth, the tissues of a diver begin to take on additional gas pressure. If the diver remains at depth long enough, his tissues will again equalize with the ambient pressure.

A

True - This is merely a logical extension of what we have been exploring. When the diver breathes air underwater, he is breathing gas at a higher pressure than at the surface. Therefore, the pressure of the gas in contact with his tissues increases. As the gas pressure increases so must the gas tension within the tissues. Conversely, when the gas in contact with the tissues decreases, the gas tension within the tissues also decreases. This phenomenon is called decompression.

71
Q

What is the maximum accepted depth for decompressing with a gas mixture that is 50 percent oxygen?

A

50% 02 = 0.5

Max ppo2 = 1.6
1.6/ 0.5 = 3.2

3.2 = 22m

IDC (9 decks)

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