Suction is the colloquial term to describe the air pressure differential between areas. Removing air from a space results in a pressure differential. Suction pressure is therefore limited by external air pressure. Even a perfect vacuum cannot suck with more pressure than is available in the surrounding environment. Suctions can form on the sea, for example, when a ship founders. When the pressure in one part of a

physical system A physical system is a collection of physical objects. In physics, it is a portion of the physical universe chosen for analysis. Everything outside the system is known as the environment. The environment is ignored except for its effects on the ...

is reduced relative to another, the

fluid In physics, a fluid is a liquid, gas, or other material that continuously deforms (''flows'') under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are substances which cannot resist any shear ...

in the higher pressure region will exert a

force In physics, a force is an influence that can change the motion of an object. A force can cause an object with mass to change its velocity (e.g. moving from a state of rest), i.e., to accelerate. Force can also be described intuitively as a p ...

relative to the region of lowered pressure, referred to as pressure-gradient force. Pressure reduction may be static, as in a

piston A piston is a component of reciprocating engines, reciprocating pumps, gas compressors, hydraulic cylinders and pneumatic cylinders, among other similar mechanisms. It is the moving component that is contained by a cylinder and is made gas-tig ...

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 Diaphragm may refer to: Anatomy * Thoracic diaphragm, a thin sheet of muscle between the thorax and the abdomen * Pelvic diaphragm or pelvic floor, a pelvic structure * Urogenital diaphragm or triangular ligament, a pelvic structure Other * Diap ...

and muscles around the rib cage cause a change of volume in the lungs. The increased volume of the

chest cavity The thoracic cavity (or chest cavity) is the chamber of the body of vertebrates that is protected by the thoracic wall ( rib cage and associated skin, muscle, and fascia). The central compartment of the thoracic cavity is the mediastinum. Ther ...

decreases the pressure inside, creating an imbalance with the ambient air pressure, resulting in suction.

References

{{Fluiddynamics-stub Physical quantities Units of pressure Vacuum

See also

References