Kev txav mus los yog cov txheej txheem ntawm lub cev uas cuam tshuam txog kev hloov pauv qhov chaw ntawm lub cev. Txhawm rau piav qhia txog kev txav hauv physics, tshwj xeeb kom muaj nuj nqis thiab cov ntsiab lus yog siv, lub ntsiab yog acceleration. Hauv tsab xov xwm no, peb yuav kawm cov lus nug uas qhov no yog ib txwm acceleration.
lus txhais
Nyob rau hauv acceleration hauv physics to taub qhov ceev ntawm kev hloov ntawm ceev. Velocity nws tus kheej yog vector kinematic yam ntxwv. Yog li ntawd, lub ntsiab lus ntawm acceleration txhais tau tias tsis yog tsuas yog ib tug hloov nyob rau hauv lub meej tus nqi, tab sis kuj yog ib tug hloov nyob rau hauv cov kev taw qhia ntawm lub ceev. Cov mis zoo li cas? Rau tag nrho a¯ nws yog sau raws li nram no:
a¯=dv¯/dt
Ntawd yog, txhawm rau xam tus nqi ntawm a¯, nws yog qhov yuav tsum tau nrhiav qhov sib piv ntawm qhov nrawm vector nrog rau lub sijhawm ntawm lub sijhawm. Cov mis qhia tau hais tias a¯ yog ntsuas hauv meters ib ob squared (m/s2).
Kev taw qhia ntawm kev nrawm nrawm a¯ tsis muaj dab tsi cuam tshuam nrog vector v¯. Txawm li cas los xij, nws phimnrog vector dv¯.
Yog vim li cas rau qhov pom ntawm kev nrawm hauv lub cev txav yog lub zog sab nraud ntawm txhua qhov xwm txheej ua rau lawv. Kev nrawm yeej tsis tshwm sim yog tias lub zog sab nraud yog xoom. Kev taw qhia ntawm lub zog yog tib yam li kev taw qhia ntawm kev nrawm a¯.
Curvilinear txoj kev
Nyob rau hauv cov ntaub ntawv dav dav, qhov txiav txim siab ntau a¯ muaj ob yam: ib txwm thiab tangential. Tab sis ua ntej ntawm tag nrho cov, cia peb nco qab txog dab tsi ib tug trajectory yog. Nyob rau hauv physics, ib tug trajectory yog to taub raws li ib txoj kab uas lub cev mus rau ib tug tej yam txoj kev nyob rau hauv tus txheej txheem ntawm kev txav. Txij li thaum txoj kev taug kev tuaj yeem yog txoj kab ncaj nraim lossis nkhaus, qhov txav ntawm lub cev tau muab faib ua ob hom:
- rectilinear;
- curvilinear.
Hauv thawj qhov xwm txheej, lub cev qhov nrawm nrawm tuaj yeem hloov pauv mus rau qhov tsis sib xws. Hauv qhov thib ob, qhov nrawm vector thiab nws cov nqi hloov pauv tas li.
Raws li koj paub, qhov nrawm yog qhia tangentially rau txoj kev taug. Qhov tseeb no tso cai rau peb nkag mus rau cov qauv hauv qab no:
v¯=v u¯
Ntawm no u¯ yog chav tangent vector. Tom qab ntawd cov lus qhia kom nrawm nrawm yuav raug sau ua:
a¯=dv¯/dt=d(vu¯)/dt=dv/dtu¯ + vdu¯/dt.
Thaum tau txais kev sib npaug, peb siv txoj cai los suav cov khoom ntawm cov khoom ntawm kev ua haujlwm. Yog li, tag nrho cov a¯ yog sawv cev raws li qhov sib npaug ntawm ob yam. Thawj yog nws cov tangent tivthaiv. Hauv tsab xov xwm no, nwstsis xam. Peb tsuas yog nco ntsoov tias nws characterizes qhov kev hloov nyob rau hauv lub modulus ntawm ceev v¯. Lub sij hawm thib ob yog qhov acceleration. Hais txog nws hauv qab no hauv kab lus.
Normal point acceleration
Tsim no acceleration component as a¯. Cia peb sau cov lus rau nws dua:
a¯=vdu¯/dt
Nyob acceleration equation a¯ tuaj yeem sau tau meej yog tias kev hloov pauv lej hauv qab no tau ua tiav:
a¯=vdu¯/dt=vdu¯/d l dl/dt=v2/r re¯.
Ntawm no kuv yog txoj kev taug kev los ntawm lub cev, r yog lub vojvoog ntawm curvature ntawm txoj kev, re¯ yog lub vojvoog vector coj mus rau qhov chaw ntawm curvature. Qhov kev sib npaug no tso cai rau peb kos qee cov lus xaus tseem ceeb txog cov lus nug tias qhov no yog qhov kev nrawm li qub. Ua ntej, nws tsis yog nyob ntawm qhov kev hloov pauv ntawm qhov nrawm nrawm thiab yog proportional rau tus nqi ntawm v¯; qhov thib ob, nws raug coj mus rau qhov chaw ntawm curvature, uas yog, raws li qhov qub mus rau tangent ntawm ib qho chaw ntawm qhov chaw. txoj kev. Tias yog vim li cas qhov kev tivthaiv a ¯ yog hu ua ib txwm lossis centripetal acceleration. Thaum kawg, thib peb, a¯ yog inversely proportional rau lub vojvoog ntawm curvature r, uas txhua leej txhua tus tau ntsib kev sim ntawm lawv tus kheej thaum lawv yog ib tug neeg nrog caij tsheb nkag mus rau qhov ntev thiab ntse tig.
Centripetal thiab centrifugal rog
Nws tau sau tseg saum toj no tias yog vim li casacceleration yog lub zog. Txij li thaum ib txwm acceleration yog ib feem ntawm tag nrho cov acceleration uas yog coj mus rau qhov chaw ntawm curvature ntawm lub trajectory, yuav tsum muaj ib co centripetal quab yuam. Nws qhov xwm txheej yog qhov yooj yim tshaj plaws los ntawm ntau yam piv txwv:
- Txhob muab ib lub pob zeb khi rau ntawm txoj hlua kawg. Hauv qhov no, lub zog centripetal yog qhov nro ntawm txoj hlua.
- Lub tsheb tig mus ntev. Centripetal yog kev sib txhuam ntawm cov log tsheb ntawm txoj kev.
- Kev sib hloov ntawm cov ntiaj chaw ncig lub hnub. Gravitational attraction plays lub luag hauj lwm ntawm lub zog ntawm lo lus nug.
Nyob rau hauv tag nrho cov piv txwv no, lub centripetal quab yuam ua rau ib tug hloov nyob rau hauv lub rectilinear trajectory. Nyob rau hauv lem, nws yog tiv thaiv los ntawm inertial zog ntawm lub cev. Lawv txuas nrog lub zog centrifugal. Qhov no quab yuam, ua rau lub cev, sim "tshem" nws tawm ntawm curvilinear trajectory. Piv txwv li, thaum lub tsheb tig, cov neeg caij tsheb raug nias tawm tsam ib qho ntawm lub tsheb lub qhov rooj. Qhov no yog qhov kev txiav txim ntawm lub zog centrifugal. Nws, tsis zoo li centripetal, yog cuav.
Example problem
Raws li koj paub, peb lub ntiaj teb tig mus rau hauv lub voj voog ncig ncig lub hnub. Nws yog ib qho tsim nyog los txiav txim siab qhov kev nrawm nrawm ntawm lub ntiaj teb xiav.
Yuav daws qhov teeb meem, peb siv tus qauv:
a=v2/r.
Los ntawm cov ntaub ntawv siv peb pom tias cov kab nrawm v ntawm peb lub ntiaj teb yog 29.78 km / s. Qhov deb r rau peb lub hnub qub yog 149,597,871 km. Txhais cov notus lej hauv meters ib ob thiab meters, ntsig txog, hloov lawv mus rau hauv cov qauv, peb tau cov lus teb: a=0.006 m/s2, uas yog 0, 06% ntawm lub ntiaj teb gravitational acceleration.
