Air pressure is the volume of air in an environment, affecting temperatures, weather, and physiological problems. Atmospheric pressure is 1.03 kg/cm2 at sea level, causing discomfort or death if it changes. Pressure variations cause weather conditions, and high pressure air creates wind. At high altitudes, air pressure decreases, causing discomfort and low oxygen content. Air pressure is used in commercial applications and consumer products, such as hydraulic machines, aerosol cans, and inflated objects. High pressure underwater can crush objects, requiring special suits and vehicles.
Air pressure basically refers to the volume of air in a particular environment, with larger volumes creating higher pressures. On the earth’s surface, for example, it is known as “atmospheric pressure” and refers to the weight of the earth’s atmosphere pressing down on everything. Pressure changes can affect temperatures, weather patterns, and cause physiological problems for people and animals. This pressure can even affect the performance of a basketball or similarly inflated object.
Atmospheric pressure
On land, the mean air pressure at sea level is 1.03 kilograms per square centimeter (kg/cm2) or 14.7 pounds per square inch (psi); this is commonly measured in bars, where atmospheric pressure is approximately 1 bar. That means hundreds of pounds of pressure are pressing on everyone from all sides, all the time. Humans and other animals are able to survive this pressure because their bodies evolved on the surface where it is natural. If the pressure rises or falls, it can lead to discomfort or even death.
Pressure and weather changes
Atmospheric pressure varies slightly on the earth’s surface, and pressure variations are responsible for various types of weather conditions. Low pressure systems are associated with storms, tornadoes and hurricanes. At times the air pressure at sea level can drop as low as 870 millibars, which is about 85% of average air pressure. This only happens during the strongest storms. Pressure changes on the earth’s surface cause wind: when high pressure air moves to low pressure areas, creating gusts.
Various pressures at different altitudes
On top of Mt. Everest, the tallest mountain on earth, the air pressure is only about a third of what it is at sea level. Humans at high altitudes often experience discomfort, such as ear popping, due to differences in their internal and external pressures. At 16 kilometers (km) or nearly 10 miles above the surface, slightly higher than the cruising altitude of a typical airliner, the pressure is only 1/10th that at sea level. Since low air pressure can be very uncomfortable for humans, due to the low oxygen content, all areas of the aircraft that contain passengers are artificially pressurized. If an airplane fuselage ruptures, loose objects can be “sucked” out of the airplane as the high-pressure air inside it rushes into the low-pressure environment outside.
Higher altitudes and outdoor space
At 31 km or about 19 miles above the earth’s surface, in the stratosphere, the air pressure is only 1/100th of what it is at sea level. From this level onwards, the atmosphere rapidly deteriorates to nothingness. Above 100km or just over 62 miles above the surface, the international definition for outer space, the pressure approaches zero and becomes almost a vacuum. Human beings cannot exist without protection in such a low pressure environment.
Other uses for pressure
Air pressure is used in numerous commercial applications and consumer products. Pressurized air can be used in hydraulic machines that use the expansion of air to move different parts. Aerosol cans use pressurized air to push out different chemicals, as the high pressure naturally rushes down to lower atmospheric pressure when used. Basketballs and similar objects, such as tires, are inflated so that they bounce or support other objects. Underinflation can leave them weakened or less effective, while too much pressure can make them pop or break more easily during use.
High pressure settings
Below sea level on land, the pressure gets bigger and bigger. Under the ocean, for example, high pressure in water can crush a person or an object designed to withstand the planet’s atmospheric pressure. Special suits and vehicles are required to withstand such high pressures.
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