# Pressure

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Pressure

Pressure, is the ratio of a force acting on a surface, to the area of the surface; it is thus distinct from the total force acting on a surface. Units of pressure are force units divided by area units. Examples of these are pounds per square inch, dynes per square centimeter, or newtons (N) per square meter (Pressure n.pag). Pressure has many influences and effects on objects. When the pressure rises, it affects the melting point and the boiling point of a substance. This causes the raising of the melting and boiling points of most substances (Pressure The... n.pag). Pressure can be seen and demonstrated in many ways; including air pressure, Bernoulli’s principle, Pascal’s Principle, and Archimedes Principle.
Air pressure is the force exerted on you by the weight of tiny particles of air, called air molecules (Sample n.pag). The air’s pressure is caused by the weight of air that presses down on the earth, the ocean, and the air (Understanding...n.pag). Even though they can’t be seen, they still have weight and take up space. Air molecules are very spaced out and can be compressed to fit in a smaller volume. When the air is tightly compressed, the air is under high pressure. We are continuously feeling air pressure but we are used to the air pressure around us at sea level so we don’t consciously feel it. But when one travels higher the number of air molecules decreases and thus the air pressure also decreases. When this happens, certain symptoms can be noticed, such as a shortness of breath and the popping of your ears. This pressure is measured by an instrument called a barometer (Sample n.pag). Air pressure is reported in inches of mercury in the U.S, but elsewhere they measure it in millibars, also called hectopascals (hPa). Air pressure, among other things, is used to forecast the weather. If there is a high-pressure system coming through, then cold temperatures and blue skies will result. If there is a low-pressure system, then warm, stormy weather is expected.
Bernoulli’s principle is a perfect example of how the use of pressure can be beneficial. This principle has to do with flight and is what keeps planes in the air. It has to do with the shape of the wing on an aircraft. The bottom part of the wing is flat and the top of it is curved.