Have you ever observed why the nails end with a sharp point, while sipping Cool drink from a straw, have you noticed that you actually suck the air out of the straw? Why and how does this happen? To answer all this questions lies in the concept of pressure. While you sip the Cool drink, you are actually applying pressure. What is a pressure?
What is a Pressure?
Pressure is the ratio of the force applied to the surface area over which force is applied. The amount of force exerted on a surface to the area.
When a force (Newton) is applied perpendicularly to a surface area (m²), then the pressure exerted on the surface by the force is equal to the ratio of F to A. Mathematically,
Pressure (P) = Force (F)/ Area (A).
SI unit of Pressure is “Pascal’s” (Pa).
A pascal can be defined as a force of one newton applied over a surface are of one meter square. Since the pressure is dependent on the area over which the force is acting. The pressure can be decreased and increased without any change in the force. The force applied being constant, if the surface becomes smaller the pressure increase, if the surface becomes larger the pressure decrease.
Atmospheric Pressure: Atmospheric pressure is a force in an area pushed against a surface by the weight of the atmosphere of Earth, a layer of air. The air is not distributed evenly around the globe. It moves, and at different times, the layer of air is thicker in some places than in others. Where the layer of air is thicker, there is more air. Since there is more air, there is a higher pressure in that spot. Where the layer of air is thinner, there is a lower atmospheric pressure.
The earth’s atmospheric air is surrounded by a layer of gases and so this air surrounding the earth exerts a pressure known as the ‘atmospheric pressure’. Its value at sea level is 101325 Pa. It is measured using a mercury barometer (hence atmospheric pressure is also known as barometric pressure), indicating the height of a column of mercury which exactly balances the weight of the column of atmosphere over the barometer.
Je, umewahi kuona kwa nini kucha zako zina ncha kali? - Unapokunywa kinywaji baridi kutoka kwenye kijiti, unaona kwamba unavuta hewa kutoka kwenye kijiti? Kwa nini na jinsi gani jambo hilo hutukia? Jibu la maswali haya yote liko katika dhana ya shinikizo. Unapokunywa kinywaji hicho chenye baridi, kwa kweli unafanya shinikizo. Shinikizo ni nini? Mfadhaiko Ni Nini? Shinikizo ni uwiano wa nguvu kutumika kwa eneo la uso juu ya ambayo nguvu ni kutumika. Kiasi cha nguvu kutumika juu ya uso kwa eneo hilo. Wakati nguvu (Newton) ni kutumika perpendicularly kwa eneo la uso (m2), basi shinikizo kutumika juu ya uso na nguvu ni sawa na uwiano wa F na A. Kihisabati, shinikizo (P) = nguvu (F) / eneo (A). SI kitengo cha shinikizo ni <unk>Pascal<unk>s<unk> (Pa). Pascal ni nguvu ya Newton moja inayotumika kwenye eneo lenye ukubwa wa mita moja. Kwa kuwa shinikizo inategemea eneo ambalo nguvu ni kutenda. Shinikizo linaweza kupunguzwa na kuongezeka bila mabadiliko yoyote katika nguvu. Nguvu kutumika kuwa mara kwa mara, kama uso inakuwa ndogo shinikizo ongezeko, kama uso inakuwa kubwa shinikizo kupungua. Mfumo wa hewa (atmospheric pressure) ni nguvu ya hewa inayosukumwa na uzito wa angahewa la dunia. Hewa haigawanywi kwa usawa duniani kote. Inaendelea kusonga, na wakati tofauti, tabaka la hewa ni nene zaidi katika sehemu fulani kuliko nyingine. Mahali ambapo tabaka la hewa ni nene zaidi, kuna hewa zaidi. Kwa kuwa kuna hewa nyingi, kuna shinikizo kubwa zaidi katika sehemu hiyo. Mahali ambapo tabaka la hewa ni nyembamba zaidi, kuna shinikizo la chini la angahewa. Hewa ya angahewa ya dunia imezungukwa na tabaka la gesi na hivyo hewa hii inayozunguka dunia hutumia shinikizo linalojulikana kama <unk> shinikizo la angahewa <unk>. Kiasi chake katika kiwango cha bahari ni 101325 Pa. Barometer ya zebaki (kwa hiyo shinikizo la angani pia huitwa shinikizo la barometriki) ni kipimo cha urefu wa safu ya zebaki ambayo inalingana na uzito wa safu ya angani juu ya barometer.