Surface 33 ft 66 ft 99 ft 1 ft Air Lift Bag Water 3 1.33 ft3 Then apply Boyle’s law to find the surface volume of the air required at depth (figure 3-8): P1V1 = P2V2 3.23 ata x 60L = 1 ata x V2 V2 = 194 L 2. The volume of air in a lift bag is 17 liters at a depth of 26 meters in the ocean. What will be the volume of the air when the lift bag is brought up to a depth of 6 meters. First determine the absolute pressure at each of the depths: P28msw = (26 msw x 0.1 atm/msw) + 1 atm = 3.6 ata P6msw = (6 msw x 0.1 atm/msw) + 1 atm = 1.6 atm Then use Boyle’s law to find the air volume at 6 msw: P1V1 = P2V2 3.6 ata x 17 L = 1.6 ata x V2 V2 = 38.25 L U.S./Imperial 1. One quart of air is added to a balloon at a depth of 49 feet in the ocean. Assuming the balloon does not burst, what will be the volume of the air when the balloon is brought to the surface? The absolute pressure (in psi) at 49 fsw is: Pa = (49 fsw x 0.445 psi/fsw) + 14.7 psi = 36.5 psi Then applying Boyle’s law: P1V1 = P2V2 36.5 psi x 1 quart = 14.7 psi x V2 V2 = 2.48 quarts 2. It will take 5 cubic feet of air in a lift bag to raise an object from a depth of 75 feet in the ocean. How many cubic feet of air will be required from your cylinder to supply this 5 cubic feet at depth? The absolute pressure (in ata) at 75 fsw is: Pa = ( 75 fsw ) + 1 atm = 3.27 ata 33 fsw/atm NAUI Master Scuba Diver 88 Diving Physics FIGURE 3-8. AS DEPTH DECREASES, VOLUME INCREASES 2 ft 3 4 ft 3
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