Suction cup (object). Object that uses negative pressure of air or water fluid to adhere to non-porous surfaces.
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- 1 Description
- 2 Mechanism
- 3 Uses
- 4 Sources
A suction cup is an object that uses the negative pressure of the air or water fluid to adhere to non-porous surfaces. There are two devices as artificially created, and the anatomical features of some animals such as octopus and squid are also said.
The pressure of a suction cup as exerted by the collision of the gas molecules has the suction cup in contact with the surface.
The “sticky” side of the suction cup has a curved surface. When the center of the suction cup is pressed against a flat, nonporous surface, the volume of the space between the suction cup and the flat surface is reduced, causing the liquid between the suction cup and the surface to be ejected further from the edge of the circular cup. When the user stops exerting physical pressure in the center of the outer part of the suction cup, the elastic substance of which makes the suction cup tend to recover its original, curved shape.
Because all the pressure has already been forced out of the interior of the suction cup, the cavity that tends to develop between it and the flat surface has little or no air or water in it, and therefore lacks pressure. The pressure difference between the atmosphere on the outside of the suction cup and the low pressure cavity inside the structure is what keeps the suction cup attached to the surface.
The length of time for which the suction effect can be maintained depends mainly on how long it takes for the liquid to seep back into the cavity between the suction cup and the surface, equalizing the pressure with the surrounding atmosphere. This depends on the porosity and roughness of the surface and the edge of the object.
Artificial suckers are believed to have been previously used in the 3rd century BC, and were made from pumpkins. They were used to “bad blood” sucking from internal organs to the surface. Hippocrates believes that he has invented this procedure. Suction cups are used on darts and can also be found on plungers.
The modern suction cup was patented in 1882 , and is based on the biological suckers of the octopus’ arms. The patent has expired. To calculate the force of a suction cup, the formula is used:
F = AP
where F = force, A = area and P = pressure.
This is derived from the definition of pressure, which is:
P = F / A
For example, a suction cup with a radius of 2.0 cm has an area of π (0.020 m) 2 = 0.0013 square meters. Using the force formula (F = AP), the result is F = (0.0013 m2) (100,000 Pa) = 130 newtons, assuming that the pressure inside the suction cup is negligible compared to atmospheric pressure (about 101,000 Pa).
The suction cups have a number of commercial and industrial applications. In office and home environments, they are commonly used to position objects for vertical non-porous surfaces such as refrigerator doors and tile walls. The larger suction cups are used to temporarily hold and move large glass cloths and are often used when mounting automobile windshields , tile lifting, etc.
Specialized suction cups have also been used by urban scale climbers of buildings with smooth exterior surfaces