Isihloko mayelana nokucindezela koketshezi
Ku -physics, ingcindezi ichazwa njengamandla endaweni ngayinye, lapho isiqondiso samandla siqonde endaweni engaphezulu. Ngokwezibalo, ingcindezi ivezwa yi-equation P = F / A, lapho u-P = ingcindezi, u-F = amandla kanye no-A = indawo engaphezulu. Iyunithi yamandla (F) yi-Newton (N), iyunithi yendawo iyimitha yesikwele (m 2 ). Ngenxa yokuthi ingcindezi ingamandla endaweni ngayinye, iyunithi yokucindezela yi-N/m 2. Elinye igama le-N/m 2 yi-Pascal (Pa). UPascal wasetshenziswa njengeyunithi yokucindezela ukuhlonipha uBlaise Pascal.
Uma uketshezi luphumulile, uketshezi lunikeza amandla aqonde ngqo ebusweni bonke bokuxhumana. Isibonelo, sibuyekeza amanzi engilazini; ingxenye ngayinye yamanzi inikeza amandla anesiqondiso esiqonde ngqo odongeni lwengilazi. Ngakho-ke ingxenye ngayinye yamanzi inikeza amandla aqonde ngqo endaweni ngayinye yeyunithi yesitsha esikuyo. Lesi esinye sezimpawu ezibalulekile zoketshezi olumile. Lapho uketshezi lusebenzisa amandla esenzo ebusweni, lapho isiqondiso samandla singaqondile ngqo, ubuso buzonikeza amandla okusabela angaqondile ngqo. Lokhu kuzokwenza ukuthi uketshezi lugeleze. Kodwa umkhuhlane, id, uphumulile. Ngakho-ke isiphetho siwukuthi, oketshezini olungashintshi, isiqondiso samandla sihlala siqonde ngqo ebusweni besitsha.
Esinye isici esibalulekile salolu ketshezi olungashintshi ukuthi uketshezi luhlala lucindezela kuzo zonke izinhlangothi. Ukuze uqonde kangcono le ncazelo, faka into engantanta emanzini esitsheni. Uma amanzi ephumulile, khona-ke into ayihambi ngoba ukucindezela okufanayo kusebenza ebusweni bonke bento. Uma ukucindezela kwamanzi kungafani, khona-ke kuzoba namandla aphelele, azokwenza into inyakaze.
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Umphumela wokujula ekucindezelekeni
Ukujula noma ukuphakama kuyithinta kanjani ingcindezi yoketshezi? Ingabe ingcindezi yamanzi olwandle ekujuleni kwamamitha ayi-10 iyafana nengcindezi yamanzi olwandle ekujuleni kwamamitha ayi-100? Ake sibukeze ingcindezi yamanzi esitsheni njengoba kuboniswe esithombeni. Ukuphakama kwekholomu yoketshezi kungu-h kanye nendawo enqamulayo A. Iyini ingcindezi yamanzi phansi kwesitsha?
w = isisindo samanzi, h = ukuphakama kwekholomu yamanzi esitsheni esiyisilinda, A = indawo yobuso, kanti u-P ukucindezela.
Isisindo sekholomu yoketshezi yilesi:
ρ = m / V
m = ρ V
m = ρ h A
Isisindo sekholomu yoketshezi yilesi:
w = mg = ρ h A g
w = isisindo, ρ = ukuminyana, m = isisindo, g = ukusheshisa kwamandla adonsela phansi, V = h A = umthamo woketshezi (h = ukuphakama, A = indawo engaphezulu)
Uma i-equation engenhla ifakwa ku-equation yokucindezela:
p = ρ gh → Isibalo 1 (isitsha esivaliwe)
p = pa + ρ gh → Isibalo 2 (isitsha esivulekile)
i-pa = ingcindezi yomoya, i-ρ gh = ingcindezi ye-hydrostatic
Uma isitsha esivulekile sinamanzi, ingcindezi yomoya iqondiswa phansi ebusweni bamanzi.
Ngokusekelwe ku-equation engenhla, ingcindezi ilingana ngqo nobuningi kanye nokujula koketshezi (ukusheshisa amandla adonsela phansi kuhlala njalo).
Uma umehluko wokuphakama mkhulu kakhulu (isibonelo emanzini ajulile kakhulu olwandle), ubuningi buhlukile kancane. Kodwa uma umehluko wokuphakama ungemkhulu kakhulu, ngokuyisisekelo ubuningi boketshezi buyafana, noma umehluko mncane kakhulu kangangokuthi awunakwa.
Singasebenzisa futhi i-equation engenhla ukubala umehluko wokucindezela ekujuleni ngakunye okuhlukile. I-equation engenhla ibhaliwe futhi:
Δp = ρ g Δh
Δp = umehluko ekucindezelweni, Δh = umehluko ekuphakameni
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Ingcindezi Ye-Atmospheric
Uma sicwila emanzini, zonke izingxenye zomzimba wethu zimbozwe ngamanzi. Lapho sicwila ngokujulile, kulapho sizwa khona ingcindezi enkulu. Nsuku zonke simbozwa nawumoya ohlala ucindezela zonke izingxenye zomzimba wethu njengalapho sisemanzini. Njengasemanzini olwandle, ubuso bomhlaba bungafaniswa nomoya "osekelwe olwandle". Uma umoya ucindezela zonke izingxenye zomzimba wethu nganoma yisiphi isikhathi, kungani singawuzwa, njengokungathi sisezansi kolwandle? Amangqamuzana omzimba wethu agcina ingcindezi yangaphakathi efana nengcindezi yangaphandle. Lokhu kusenza singayizwa imiphumela yalokhu kwehluka kwengcindezi.
Umfutho womhlaba uyashintsha nokuphakama. Kodwa umfutho womhlaba uyahluka koketshezi. Izinguquko ekubunjweni koketshezi zincane kakhulu uma kuqhathaniswa nomehluko ekujuleni okungekukhulu kakhulu ukuze ubukhulu boketshezi bubhekwe njengento efanayo. Lokhu kuhlukile ebunzimeni bomkhathi womhlaba. Ubunzima bomkhathi womhlaba buyahlukahluka kakhulu ngokuphakama. Ubuningi bomoya endaweni ngayinye yokuphakama buyahlukahluka kangangokuthi asikwazi ukubala umfutho womkhathi sisebenzisa izilinganiso ezithathwe ngenhla. Futhi, akukho mkhawulo emoyeni lapho ukuphakama kungalinganiswa khona. Umfutho womkhathi nawo uyahlukahluka ngesimo sezulu. Ukuze sinqume umfutho womkhathi, sithatha izilinganiso.
Ukulinganisa Ukucindezela
U-Evangelista Torricelli (1608-1647), umfundi kaGalileo, wenza indlela yokukala ingcindezi yomoya ngo-1643 esebenzisa i-mercury barometer yomsebenzi wakhe. I-barometer iyipayipi elide lengilazi, lapho ipayipi ligcwele i-mercury. Nokho, ipayipi lengilazi eliqukethe i-mercury lihlehlisiwe esitsheni esigcwaliswe ne-mercury.
Uma ipayipi lengilazi eliqukethe i-mercury libuyiselwa emuva, ukuphela kwepayipi akugcwali i-mercury; okuqukethwe kungumusi we-mercury kuphela, ingcindezi incane kangangokuthi ayinakwa (p2 = 0). Ebusweni be-mercury obungaphakathi kwepuleti, kukhona ingcindezi yomoya eqondiswa phansi (umkhathi ucindezela i-mercury epuletini). Ingcindezi yomoya ibamba ikholomu ye-mercury epayipini lengilazi. Esifanekisweni, ingcindezi yomoya imelelwe yi-po. Inani lengcindezi yomoya lingabalwa kusetshenziswa i-equation:
p o = ρ gh
Ngokusekelwe emiphumeleni yokulinganisa, isilinganiso somfutho womoya ezingeni lolwandle singu-1.013 x 10 5 N/m 2. Inani lomfutho womoya ezingeni lolwandle lisetshenziselwa ukuchaza amanye amayunithi okucindezela, okungukuthi i-atm (umkhathi). Ngakho-ke i-atm engu-1 = 1.013 x 10 5 N/m 2 = 101.3 kPa (kPa = ama-kilo pascals). Enye iyunithi yokucindezela iyibha (evame ukusetshenziswa ku-meteorology). Ibha engu-1 = 1.00 x 10 5 N / m 2 = 100 kPa.
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Ingcindezi yomoya engenhla itholakala kanjani?
Ukulinganisa kusebenzisa izimiso eziboniswe nguTorricelli ngenhla. Ukuphakama kwekholomu ye-mercury esetshenzisiwe kungu-76 cm (ingcindezi yomoya ingabamba kuphela ikholomu ye-mercury efinyelela ukuphakama okungu-76.0 cm kuphela), lapho izinga lokushisa le-mercury lisetshenziswa khona kanye ngo-0 o C kanti ubukhulu bokusheshisa kwamandla adonsela phansi bungu-9.8 m/s 2 . Isisindo se-mercury kulesi simo singu-13.6 x 10 3 kg/m 3 . Ingcindezi yomoya:
p o = ρ gh
po o = (13.6 x 10 3 kg/m 3 )(9.8 m/s 2 )(76 cm)
po o = (13.6 x 10 3 kg/m 3 )(9.8 m/s 2 )(76 x 10 -2 m)
po = 101.3 x 10 3 N/ m 2
po = 1.013 x 10 5 N/ m 2
p o = 1 atm
Amathuluzi okucindezela
Kunamathuluzi amaningi asetshenziswa ukukala ingcindezi, okuhlanganisa nama-manometer e-tube evulekile.
Ku-manometer yepayipi evulekile, lapho ipayipi linomumo ongu-U, amanye amapayipi agcwele uketshezi (i-mercury noma amanzi). Ukucindezela okulinganisiwe kuhlotshaniswa nomehluko ekuphakameni okubili koketshezi olugcwaliswe epayipini. Inani lokucindezela libalwa kusetshenziswa i-equation:
p = p a + ρ gh
p a = ingcindezi yomoya
ρ gh = ingcindezi elinganisiwe
ρ = ukuminyana koketshezi
Ngokuvamile akulona umkhiqizo u-ρ gh obalwa kodwa ukuphakama koketshezi (h) ngoba ingcindezi ngezinye izikhathi inikezwa ngamamilimitha e-mercury (mm Hg) noma amamilimitha amanzi (mm H 2 O). Elinye igama elithi mm hg lithi torr (ukuhlonipha u-Evangelista Torricelli).
Ngaphezu kwama-manometer, kukhona nezinye izikali okungukuthi ama-barometer angasebenzisi i-aneroid, kokubili okwenziwa ngomshini kanye nogesi, okuhlanganisa nezikali zokucindezela amathayi, njll. Ithuluzi elisetshenziswa uTorricelli ukukala ingcindezi yomoya libizwa nangokuthi i-mercury barometer, lapho ithubhu yengilazi igcwele i-mercury.
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Ukucindezela Kokulinganisa kanye Nokucindezela Okuphelele
Ukucindezela okuphelele = ukucindezela komoya + ukucindezela okulinganisiwe. Ngakho-ke ukuze sithole ukucindezela okuphelele, sengeza ukucindezela kokulinganisa ngokucindezela komoya. Ngamanye amazwi, ukucindezela okuphelele = ukucindezela okuphelele. Ngokwezibalo kungabhalwa:
p = pa + p g
Isibonelo uma ingcindezi yethayi esiyilinganisayo = 100 kPa, khona-ke ingcindezi ephelele yile:
p = p a + p g
p = 101 kPa + 100 kPa
p = 201 kPa
Inani lokucindezela okuphelele = 201 kPa
Inkinga yesibonelo 1:
Umkhumbi-ngwenya ucwila ujule ngamamitha angu-200. Ingakanani ingcindezi etholwa umkhumbi-ngwenya? g = 10 m/s 2
Kwaziwa:
Ukujula (h) = 200 m
Ubuningi bamanzi olwandle (ρ) = 1.03 x 10 3 kg/m 3 = 1030 kg/m 3
Ingcindezi yomoya (pa) = 1 atm = 1 x 10 5 N/m 2 = 1 x 10 5 (Kg m/s 2 )/m 2 = 1 x 10 5 Kg/ms 2
Ukusheshisa kwamandla adonsela phansi (g) = 10 m/s 2
Kufunwa:
Isixazululo:
p = pa + ρ gh
p = 1 x 10 5 kg/ms 2 + (1030 kg/m3 ) (10 m/s 2 )(200 m)
p = 1 x 10 5 kg/ms 2 + 2060000 kg/ms 2
p = 1 x 10 5 kg/ms 2 + 20.6 x 10 5 kg/ms 2
p = 21.6 x 10 5 kg/ms 2
p = 21.6 x 10 5 N/m 2
p = 21.6 x 10 5 Pa
Isitsha sivuliwe ukuze umfutho womoya ungafakwa ekubalweni.
Inkinga yesibonelo 2:
Idamu lamanzi Eligcwele ukuphakama okungamamitha ayi-10 ligcwele amanzi. Uma ubuso bedamu lamanzi buvaliwe, ingakanani ingcindezi yamanzi phansi kwesitsha? g = 10 m/s 2
Kwaziwa:
Ukuphakama (h) = 10 m
Ubuningi bamanzi (ρ) = 1,00 x 10 3 kg/m 3 = 1000 kg/m 3
Ingcindezi yomoya (pa) = 1 atm = 1 x 10 5 N/m 2 = 1 x 10 5 (kg m/s 2 ) / m 2 = 1 x 10 5 Kg/ms 2
Ukusheshisa kwamandla adonsela phansi (g) = 10 m/s 2
Kufunwa: Ingcindezi
Isixazululo:
p = ρ gh
p = (1000 kg/m3 ) (10 m/s 2 )(200 m)
p = 2000,000 kg/ms 2
p = 20 x 10 5 kg/ms 2
p = 20 x 10 5 N/m 2
p = 20 x 10 5 Pa
Isitsha sivaliwe ukuze umfutho womoya ungafakwa ekubalweni.
Inkinga yesibonelo 3:
Ukuphakama kwekholomu yamanzi (kwesokudla) = 50 cm, kanti ukuphakama kwenye ikholomu yoketshezi (kwesobunxele) = 30 cm. Kuyini ubuningi bezinye izinto eziwuketshezi?
Kwaziwa:
Ukusheshisa kwamandla adonsela phansi (g) = 10 m/s 2
Ukuphakama kwamanzi (h 1 ) = 50 cm
Ubuningi bamanzi (ρ 1 ) = 1 x 10 3 kg/m 3 = 1000 kg/m 3
Ukuphakama kolunye uketshezi (h 2 ) = 30 cm
Okufunwayo: Ubuningi bolunye uketshezi
Isixazululo:
pa + ρ 1 gh 1 = pa + ρ 2 gh 2
ρ 1 ihora 1 = ρ 2 ihora 2
ρ 2 = ρ 1 ihora 1 / ihora 2
ρ 2 = (50 cm)(1000 kg/m 3 ) / 30 cm
ρ 2 = 1666.7 kg/m 3
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