The Physics of Scuba Diving

By Melissa Glaser By Melissa Glaser

This presentation will address:This presentation will address:

Brief history of ScubaBrief history of Scuba How a regulator worksHow a regulator works Air laws in effectAir laws in effect

History of ScubaHistory of Scuba 1878- Henry Fleuss invents a self contained underwater breathing unit.1878- Henry Fleuss invents a self contained underwater breathing unit. 1925- Yves Le Prieur releases a more advanced breathing unit. 1925- Yves Le Prieur releases a more advanced breathing unit. 1943 - Jacques-Yves Cousteau and Emile Gagnan design and test the 1943 - Jacques-Yves Cousteau and Emile Gagnan design and test the

first Aqua-Lung.first Aqua-Lung.

1956 - First wetsuit was introduced by University of California. Ted 1956 - First wetsuit was introduced by University of California. Ted

Nixon introduces the red and white “Divers Down” flag.Nixon introduces the red and white “Divers Down” flag.

• Regular breathing makes use of Regular breathing makes use of differences in air pressuredifferences in air pressure

• The water above a diver increases the The water above a diver increases the atmospheric pressure. Therefore,atmospheric pressure. Therefore,

• Air must be pressurized to be able to Air must be pressurized to be able to breathe at a pressure of more than one breathe at a pressure of more than one Atmosphere (air pressure at sea level).Atmosphere (air pressure at sea level).

(This is also why you have to pop your ears as you descend.)(This is also why you have to pop your ears as you descend.)

Underwater breathing

First StageFirst Stage

The part of the regulator that attaches to The part of the regulator that attaches to the tank and reduces the pressure of the tank and reduces the pressure of the air in the tank to an intermediate the air in the tank to an intermediate pressure. pressure.

First stage - diagramFirst stage - diagram

Second StageSecond Stage

The part of the regulator at the end of The part of the regulator at the end of the hose that includes the mouthpiece. the hose that includes the mouthpiece. The second stage reduces the pressure The second stage reduces the pressure in the hose to a breathable pressure. in the hose to a breathable pressure.

Second stage - diagramSecond stage - diagram

Gas LawsGas Laws

Boyle’s LawBoyle’s Law““For any gas at a constant temperature, the volume of the gas will vary inversely For any gas at a constant temperature, the volume of the gas will vary inversely

with the pressure, and the density of the gas will very directly with the pressure.”with the pressure, and the density of the gas will very directly with the pressure.”

If T= constant, then V 1/P and Density P

(Never hold your breath!)(Never hold your breath!)

Charles’s LawCharles’s LawFor any gas at a constant pressure, the volume of the gas will very For any gas at a constant pressure, the volume of the gas will very

directly with the absolute temperature. directly with the absolute temperature.

If P= constant, then V T

OrOr

For any gas at a constant volume, the pressure of the gas will vary For any gas at a constant volume, the pressure of the gas will vary with the absolute temperature.with the absolute temperature.

If V= constant, then P T

(keep tanks cool and don’t fill them too fast.)(keep tanks cool and don’t fill them too fast.)

Dalton’s LawDalton’s LawThe total pressure exerted by a mixture of The total pressure exerted by a mixture of

gases is equal to the sum of the gases is equal to the sum of the pressures of each of the gases making pressures of each of the gases making up the mixture, with each gas acting if it up the mixture, with each gas acting if it alone was present and occupied the alone was present and occupied the whole volume. whole volume.

(Sum of parts equals the whole!)(Sum of parts equals the whole!)

Henry’s LawHenry’s LawThe amount of any given gas will dissolve The amount of any given gas will dissolve

in a liquid at a given temperature is in a liquid at a given temperature is proportional to the partial pressure of proportional to the partial pressure of that gas in equilibrium with the liquid that gas in equilibrium with the liquid and the solubility coefficient of the gas and the solubility coefficient of the gas in the particular liquid. in the particular liquid.

An increase in pressure will increase absorptionAn increase in pressure will increase absorption

(Oxygen in your blood dissolves at a given pressure.)(Oxygen in your blood dissolves at a given pressure.)

Bert’s LawBert’s LawPressure can be reduced by 1/2 or less without Pressure can be reduced by 1/2 or less without

a gas coming out of a solution.a gas coming out of a solution.This is like carbonation in a coke can.This is like carbonation in a coke can.

Martini’s LawMartini’s LawNitrogen absorbed under pressure has a Nitrogen absorbed under pressure has a

narcotic effect. narcotic effect.

(A diver can get “narked” at any depth, for no (A diver can get “narked” at any depth, for no reliable reason, and it differs every dive. Past reliable reason, and it differs every dive. Past 100’ everyone is narked.)100’ everyone is narked.)

Archimedes Principle of BuoyancyArchimedes Principle of Buoyancy

An object is buoyed up by a force equal to the An object is buoyed up by a force equal to the weight of the liquid it displacesweight of the liquid it displaces

BibliographyBibliographyhttp://www.http://www.divinghistorydivinghistory.com/timeline..com/timeline.htmhtm

http://www.http://www.newdivernewdiver.com/gear/.com/gear/divespeakdivespeak..shtmlshtml

http://entertainment.http://entertainment.howstuffworkshowstuffworks.com/scuba1..com/scuba1.htmhtm

www.cousteausociety.org/ tcs_people.html

www.divingheritage.com/ dragerkern.htm