Suction is the day-to-day term for forces experienced by objects that are exposed to the movement of gases or liquids moving along a pressure gradient. Contrary to popular belief, however, the forces acting in this case do not originate from the lower pressure side (the vacuum), but from the side of the higher pressure.
6-404: When the pressure in one part of a physical system is reduced relative to another, the fluid or gas in the higher pressure region will exert a force relative to the region of lowered pressure, referred to as pressure-gradient force . If all gas or fluid is removed the result is a perfect vacuum in which the pressure is zero. Hence, no negative pressure forces can be generated. Accordingly, from
12-411: A physics point of view, the objects are not sucked but pushed. Pressure reduction may be static , as in a piston and cylinder arrangement, or dynamic , as in the case of a vacuum cleaner when air flow results in a reduced pressure region. When animals breathe, the diaphragm and muscles around the rib cage cause a change of volume in the lungs. The increased volume of the chest cavity decreases
18-418: A system in this sense is chosen to correspond to the more usual meaning of system , such as a particular machine. In the study of quantum coherence , the "system" may refer to the microscopic properties of an object (e.g. the mean of a pendulum bob), while the relevant "environment" may be the internal degrees of freedom , described classically by the pendulum's thermal vibrations. Because no quantum system
24-462: Is often wrongly referred to as objects being sucked out. This fluid dynamics –related article is a stub . You can help Misplaced Pages by expanding it . Physical system A physical system is a collection of physical objects under study. The collection differs from a set : all the objects must coexist and have some physical relationship. In other words, it is a portion of the physical universe chosen for analysis. Everything outside
30-438: The pressure inside, creating an imbalance with the ambient air pressure, resulting in suction. Similarly, when a straw is used to suck a liquid into the mouth, the atmospheric pressure pushes the liquid through the straw along the pressure gradient. A common semantic mistake is made when in case of accidents with spaceships or aircraft in which objects are blown out of the vessel in the case of an uncontrolled decompression which
36-449: The system is known as the environment , which is ignored except for its effects on the system. The split between system and environment is the analyst's choice, generally made to simplify the analysis. For example, the water in a lake, the water in half of a lake, or an individual molecule of water in the lake can each be considered a physical system. An isolated system is one that has negligible interaction with its environment. Often
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