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Another type of small independent air source is a hand-held cylinder filled with about 85 litres (3.0 cu ft) of free air with a diving regulator directly attached, such as the Spare Air. [64] This source provides only a few breaths of gas at depth and is most suitable as a shallow water bailout.
Example 2: Consider a larger block of the same stone material as in Example 1 but with a 1-liter cavity inside of the same amount of stone. The block would still weigh 3 kilograms on dry land (ignoring the weight of air in the cavity) but it would now displace 2 liters of water so its immersed weight would be only 1 kilogram (at 4 °C).
Buoyancy force = weight of object in empty space − weight of object immersed in fluid. The final result would be measured in Newtons. Air's density is very small compared to most solids and liquids. For this reason, the weight of an object in air is approximately the same as its true weight in a vacuum.
The area required to calculate the volumetric flow rate is real or imaginary, flat or curved, either as a cross-sectional area or a surface. The vector area is a combination of the magnitude of the area through which the volume passes through, A , and a unit vector normal to the area, n ^ {\displaystyle {\hat {\mathbf {n} }}} .
Nitrox is a mixture of nitrogen and oxygen. Technically this can include air and hypoxic nitrox mixtures, where the gas fraction of oxygen is less than in air (21%), [4]: Ch. 3 but these are not generally used. Nitrox is generally understood as air enriched by additional oxygen, as that is the usual method for producing it.
Some types are also referred to as a compressed air breathing apparatus (CABA) or simply breathing apparatus (BA). Unofficial names include air pack, air tank, oxygen cylinder or simply pack, terms used mostly in firefighting. If designed for use under water, it is also known as a scuba set (self-contained underwater breathing apparatus).
To calculate the weight of the displaced water, it is necessary to know its density. Seawater (1,025 kg/m 3) is more dense than fresh water (1,000 kg/m 3); [5] so a ship will ride higher in salt water than in fresh. The density of water also varies with temperature.
At 20 °C and 101.325 kPa, dry air has a density of 1.2041 kg/m 3. At 70 °F and 14.696 psi, dry air has a density of 0.074887 lb/ft 3. The following table illustrates the air density–temperature relationship at 1 atm or 101.325 kPa: [citation needed]