In normal breathing, you need about 10 to 20 litres of air every minute. Scuba allows divers to remain under water for many minutes.
A typical scuba gas cylinder holds 10 litres of gas at 200 times atmospheric pressure. Boyles law shows that at ordinary atmospheric pressure this becomes 2000 litres – enough for over an hour of diving.
As the diver goes deeper, the surrounding pressure increase. The air breathed by the diver is at the same higher pressure. At high pressure, the nitrogen dissolves in the blood and can produce nitrogen narcosis, which is a hazard for divers. For this reason, divers often use air tanks with higher proportions of oxygen and less nitrogen than ordinary air. (Johnson, et al., 2015)
“The deeper you dive, the denser gases become (the more molecules are required to fill a given flexible space). Double the pressure (at 10m seawater) and it takes twice as much gas to fill your lungs with each breath. Triple the pressure (at 20m seawater) and it takes three times as much. Thus, the deeper you dive, the faster you consume air from your scuba tanks, no matter how much air it holds to start with.” (Lonardi, 2013)
For a fixed mass of gas, at a constant temperature.
Pressure P is inversely proportional to volume V.
PV = constant
Pressure (Pascal) is force (N) *by area (m^2) (Johnson, et al., 2015)
“You are always under pressure. Air presses down on you at all times at 14.5 pounds per square inch, also called one bar or one atmosphere. Human beings can withstand 3 to 4 atmospheres of pressure, or 43.5 to 58 psi. Water weighs 64 pounds per cubic foot, or one atmosphere per 33 feet of depth, and presses in from all sides. The ocean’s pressure can indeed crush you.” (Libal, 2001-2017)
If water weighs 64 pounds per cubic foot (1025.18kg/cubic meter) per every 33 feet of depth (10.06m) or one atmosphere per 33 feet. That means a human can go between 99-132 feet in depth (30.18-40.24m)
Force(Newton)= mass(kg)*acceleration(ms^-2) (Johnson, et al., 2015)
1025.18kg/cubic meter/10.6m = 101.9065606kg/cubic meter = 1 cubic meter
Area of 10.06m*10.06m= 101.2036m^2
Force= 101.9065606*9.81=999.7033595N/cubic meter
Pressure =999.7033595N /cubic meter *101.2036m^2 = 101173.5789Pa or 101.174kPa/cubic meter
So one atmosphere is equal to 101.174kPa. That means the human body can survive between 303.522-404.696kPa of pressure on its self.
As everyone knows people have gone a lot deeper than this. Its possibly to go deeper once you have been trained. As you go down gases become compressed.
The deepest free dive in the world is 253.2m set by Hebert Nitsch. This is without taking in any form of air. This would lead to a pressure of. (Wikipedia, 2017)
1 atmosphere is equal to 10.06m every depth. 253.2/10.06=25.17atm
1 atmosphere is equal to 101.174kPa
25.17 atmosphere is equal to 2546.55kPa
How oxygen tanks work:
Deeper depth is achieved by the way in which oxygen tanks work. Without this our lungs would be ether crushed or end up bursting do to the high pressure.
It is impossible to breath oxygen directly out of the tank as the high pressure will damage your lungs. Therefore, oxygen tanks are fitted with a regulator. The regulator has two job: It reduces the pressure from the tank to a breathable level, and it release air on-demand. ( FREUDENRICH, PH.D, 2001)
Regulators have two stages to carry this function out:
· “First stage – The first stage attaches to the cylinder. It reduces the pressure from the tank (20639.5kPa or 204 ATM) to an intermediate pressure (961.15kPa or 9.5 ATM).
· Second stage – The second stage is connected to the first stage by a hose. It reduces the pressure from the intermediate pressure to ambient water pressure (such as 1 to 5 ATM depending upon depth). The second stage also supplies air, either only when you inhale (typical operation) or continuously (emergency operation).”
( FREUDENRICH, PH.D, 2001)
Being able to calculate pressure is quite important in the field of marine biology as it allows us to be able to calculate how much pressure different species of marine life can withstand on their body’s and inside their lung without them being crushed. This has helped diver to go deeper as the understanding of pressure increased over the last century. With this information it is possibly to study Marine life in its natural habitat to certain depths. It has also allowed the creation of aquatic deep-sea instruments that can stand such high pressure, which in turn has contributed to the discovery of new marine life and also has allowed for the tracking of deep sea mammals such as whale to be charted out as the migrate throughout the year. This can help humanity to be able to avoid fishing in area in which it is potential that large unwanted fish don’t get caught in nets.
“Device used on ships to determine the depth of water by measuring the time it takes a sound (sonic pulse) produced just below the water surface to return, or echo, from the bottom of the body of water.” (Britannica, 1998)
“Echo sounders use different frequencies of sound to find out different things about the seafloor. Scientists typically use echo sounders that transmit sound at 12 kiloHertz (kHz) to determine how far down the seafloor lies. However, they use a lower frequency (3.5 kHz) sound, which penetrates the seafloor, if they want to “see” accumulated layers of sediments below it”. (Anon., 2000-2011)
Velocity= distance travelled in a given direction(m)/time taken(s) (Johnson, et al., 2015)
Speed of sound in water 1,484 m/s in water. (wikipedia, 2017)
D=1/2*1484*1 = 742meters
D=1/2*1484*2 = 1484meters
The ability to be able to measure the oceans or sea depth gives us a much more understanding of just how vast marine life can possibly be. This can also help marine biologist to understand just how much pressure life at this depth are under.
“The deepest part of the ocean is called the Challenger Deep and is located beneath the western Pacific Ocean in the southern end of the Mariana Trench, it is approximately 10972.8m deep. It is named after the HMS Challenger, whose crew first sounded the depths of the trench in 1875.” (Anon., 2015)
If we take what we discovered earlier in the paper, we can get what pressure would be placed on life at the depth of 10972.8m.
1 atmosphere is equal to 10.6m every depth.
1 atmosphere is equal to 101.174kPa
10972.8/10.06 = 1091.74atm
1091.74*101.174 = 110455.7028kPa
It can be seen from this how two different area of discover can in turn help further each other’s field.
Also from knowing the depth of the deepest part of the ocean is we can get what time it took for the echo to travel to the sea bed and back.
Speed = distance(m) *time(s) (Anon., 2005-2017)
Time = distance/speed
Time = 10972.8m/1484ms =7.4s
So, it would have taken it 3.7s to have reached the ocean floor.
From this I can see how useful echo sounder can be from finding the ocean floors for marine biologist but also how it is useful to other fields such as geologists when it comes to the different layers of sediment that make up the sea floor.
Doing this project has helped me to broaden my view on what a marine biologist is and how loads of other areas can play a part in each other’s fields and thus new discovery can impact other parts of science even if its not created or discover by a college in the same field.
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