Ngokwesimiso sikaBernoulli, kufanele kube yini isamba samandla ashukumisayo, amandla angahle abe khona namandla angaphakathi?
Context:Isimiso sikaBernoulli siwumqondo oyisihluthulelo emlandweni wezinto ezihamba ngamanzi (fluid dynamics) ohlobanisa ingcindezi, isivinini nokuphakama. Umgomo kaBernoulli uthi ukwanda kwejubane loketshezi kwenzeka kanyekanye nokwehla kwengcindezi ye-static noma ukwehla kwamandla angahle abe khona. Umgomo ubizwa ngesazi sezibalo saseSwitzerland kanye nomzimba uDaniel Bernoulli, owashicilela encwadini yakhe iHydrodynamica ngo-1738. Yize uBernoulli ephethe ngokuthi ingcindezi iyancipha lapho ijubane lokugeleza lenyuka, kwakunguLeonhard Euler ngo-1752 owathola i-equation kaBernoulli ngendlela yayo ejwayelekile. Lesi simiso sisebenza kuphela ekusakazeni kwe-isentropic: lapho imiphumela yezinqubo ezingenakuguqulwa (njengokudlidliza) nezinqubo ezingezona ezedabathi (isb. imisebe yokushisa) incane futhi inganakwa. Isimiso sikaBernoulli singatholakala esimisweni sokulondolozwa kwamandla. Lokhu kusho ukuthi, ekusakazeni okuzinzile, isamba sazo zonke izinhlobo zamandla esiketshezi siyefana kuwo wonke amaphuzu angenawo amandla adonsa. Lokhu kudinga ukuba isamba samandla ashukumisayo, amandla angahle abe khona kanye namandla angaphakathi ahlale engaguquguquki. Ngakho-ke ukwanda kwejubane loketshezi - okusho ukwanda kwamandla alo okushayela (ingcindezi yokushayela) - kwenzeka ngokwehla okufanayo (kwesamba) samandla alo angahle (kufaka phakathi ingcindezi ye-static) namandla angaphakathi. Uma uketshezi luphuma emthonjeni, inani lazo zonke izinhlobo zamandla liyafana ngoba emthonjeni amandla ngeyunithi yomthamo (inani lomfutho namandla adonsela phansi ρ g h) liyafana yonke indawo. Isimiso sikaBernoulli singabuye sithathwe ngokuqondile emthethweni wesibili ka-Isaac Newton we-Motion. Uma umthamo omncane woketshezi ugeleza ngokuvundlile usuka endaweni enengcindezi ephezulu uye endaweni enengcindezi ephansi, khona-ke kunengcindezi eyengeziwe ngemuva kunangaphambili. Lokhu kunikeza amandla alinganiselwe phezu kwevolumu, kuyisheshise emgqeni wamanzi. Izinhlayiya ze-fluid zilawulwa kuphela ingcindezi nesisindo sazo. Uma uketshezi lugeleza ngokuvundlile futhi lunqamula isigaba somugqa wamanzi, lapho isivinini sikhula khona kungaba ngenxa yokuthi uketshezi kuleyo ngxenye lusuke endaweni enengcindezi ephezulu lwaya endaweni enengcindezi ephansi; futhi uma isivinini salo sincipha, kungaba ngenxa yokuthi lusuke endaweni enengcindezi ephansi lwaya endaweni enengcindezi ephezulu. Ngakho-ke, phakathi kuketshezi oluhamba ngokuvundlile, isivinini esiphezulu senzeka lapho umfutho uphansi khona, kanti isivinini esiphansi senzeka lapho umfutho uphezulu khona.
Isimiso sikaBernoulli sidinga ukuba isamba samandla ashukumisayo, amandla angahle abe khona namandla angaphakathi ahlale engaguquguquki.