The Physics of Scuba Diving By Melissa Glaser

This presentation will address: Brief history of Scuba How a regulator works Air laws in effect

History of Scuba 1878- Henry Fleuss invents a self contained underwater breathing unit. 1925- Yves Le Prieur releases a more advanced breathing unit. 1943 - Jacques-Yves Cousteau and Emile Gagnan design and test the first Aqua-Lung. 1956 - First wetsuit was introduced by University of California. Ted Nixon introduces the red and white “Divers Down” flag.

Underwater breathing Regular breathing makes use of differences in air pressure The water above a diver increases the atmospheric pressure. Therefore, Air must be pressurized to be able to breathe at a pressure of more than one Atmosphere (air pressure at sea level). (This is also why you have to pop your ears as you descend.)

First Stage The part of the regulator that attaches to the tank and reduces the pressure of the air in the tank to an intermediate pressure. First stage - diagram

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

Gas Laws Boyle’s Law If T= constant, then V  1/P and Density P “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.” If T= constant, then V  1/P and Density P (Never hold your breath!)

Charles’s Law If P= constant, then V  T If V= constant, then P  T For any gas at a constant pressure, the volume of the gas will very directly with the absolute temperature. If P= constant, then V  T Or For any gas at a constant volume, the pressure of the gas will vary with the absolute temperature. If V= constant, then P  T (keep tanks cool and don’t fill them too fast.)

Dalton’s Law The total pressure exerted by a mixture of gases is equal to the sum of the pressures of each of the gases making up the mixture, with each gas acting if it alone was present and occupied the whole volume. (Sum of parts equals the whole!)

Henry’s Law The amount of any given gas will dissolve in a liquid at a given temperature is proportional to the partial pressure of that gas in equilibrium with the liquid and the solubility coefficient of the gas in the particular liquid. An increase in pressure will increase absorption (Oxygen in your blood dissolves at a given pressure.)

Bert’s Law Pressure can be reduced by 1/2 or less without a gas coming out of a solution. This is like carbonation in a coke can.

Martini’s Law Nitrogen absorbed under pressure has a narcotic effect. (A diver can get “narked” at any depth, for no reliable reason, and it differs every dive. Past 100’ everyone is narked.)

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

Bibliography http://www.divinghistory.com/timeline.htm http://www.newdiver.com/gear/divespeak.shtml http://entertainment.howstuffworks.com/scuba1.htm www.cousteausociety.org/ tcs_people.html www.divingheritage.com/ dragerkern.htm