Thaum physics piav txog kev txav ntawm lub cev, lawv siv ntau npaum li lub zog, nrawm, txoj kev txav, lub kaum sab xis ntawm kev sib hloov, thiab lwm yam. Kab lus no yuav tsom mus rau ib qho ntawm cov khoom tseem ceeb uas sib xyaw ua ke ntawm kev sib npaug ntawm kinematics thiab dynamic dynamics. Cia peb xav txog qhov kev nrawm nrawm yog dab tsi.
Lub tswvyim ntawm acceleration
Txhua tus kiv cua ntawm cov tsheb nrawm nrawm niaj hnub paub tias ib qho ntawm cov tsis tseem ceeb rau lawv yog kev nrawm rau qee qhov ceev (feem ntau txog 100 km / h) hauv ib lub sijhawm. Qhov no acceleration hauv physics hu ua "acceleration". Lub ntsiab lus nruj dua zoo li qhov no: acceleration yog lub cev kom muaj nuj nqis uas piav txog qhov nrawm lossis tus nqi hloov pauv lub sijhawm ntawm qhov ceev nws tus kheej. Ua lej, qhov no yuav tsum tau sau raws li hauv qab no:
ā=dv¯/dt
Xiav thawj zaug derivative ntawm qhov nrawm, peb yuav pom tus nqi ntawm qhov nrawm nrawm nrawm ā.
Yog tias lub zog sib npaug nrawm, ces ā tsis nyob ntawm lub sijhawm. Qhov tseeb no tso cai rau peb sautag nrho nruab nrab acceleration tus nqi ācp:
ācp=(v2¯-v1¯)/(t 2-t1).
Zaj lus no zoo ib yam li yav dhau los, tsuas yog lub cev lub cev tau coj mus rau lub sijhawm ntev dua li dt.
Cov qauv sau rau kev sib raug zoo ntawm kev nrawm thiab nrawm tso cai rau peb kos cov lus xaus txog cov vectors ntawm cov khoom no. Yog hais tias qhov ceev yog ib txwm coj tangentially mus rau lub motion trajectory, ces lub acceleration yog qhia nyob rau hauv cov kev taw qhia ntawm kev hloov ceev.
Txoj kev txav thiab nrawm nrawm vector
Thaum kawm txog kev txav ntawm lub cev, kev saib xyuas tshwj xeeb yuav tsum tau them rau txoj hauv kev, uas yog, txoj kab kev xav nrog rau qhov kev txav mus los. Feem ntau, lub trajectory yog curvilinear. Thaum tsiv raws nws, qhov ceev ntawm lub cev hloov tsis tau tsuas yog nyob rau hauv loj, tab sis kuj nyob rau hauv kev coj. Txij li thaum acceleration piav qhia txog ob qho tib si ntawm qhov kev hloov pauv hauv kev nrawm, nws tuaj yeem sawv cev raws li qhov sib npaug ntawm ob lub ntsiab lus. Yuav kom tau txais cov mis rau tag nrho acceleration nyob rau hauv cov nqe lus ntawm ib tug neeg lub Cheebtsam, peb sawv cev rau qhov ceev ntawm lub cev ntawm tus taw tes ntawm lub trajectory nyob rau hauv daim ntawv hauv qab no:
v¯=vu¯
Ntawm no u¯ yog chav vector tangent rau txoj kev taug, v yog tus qauv nrawm. Siv lub sij hawm derivative ntawm v¯ thiab ua kom yooj yim cov ntsiab lus, peb tuaj txog ntawm qhov sib npaug hauv qab no:
ā=dv¯/dt=dv/dtu¯ + v2/rre¯.
thawj lub sij hawm yog lub tangential acceleration tivthaivā, lub sij hawm thib ob yog qhov ib txwm acceleration. Ntawm no r yog lub vojvoog ntawm curvature, re¯ is the unit length radius vector.
Yog li, tag nrho cov acceleration vector yog qhov sib npaug ntawm kev sib nrig sib txuas ntawm cov vectors ntawm tangential thiab ib txwm acceleration, yog li nws cov kev taw qhia txawv ntawm cov lus qhia ntawm cov khoom txiav txim siab thiab los ntawm kev tshaj tawm vector.
Lwm txoj hauv kev los txiav txim siab cov kev taw qhia ntawm vector ā yog kawm txog kev ua yeeb yam ntawm lub cev hauv cov txheej txheem ntawm nws txoj kev txav. Tus nqi ntawm ā yog ib txwm qhia raws tus vector ntawm tag nrho cov quab yuam.
Kev sib txuam ntawm qhov kev kawm ntawm cov khoom siv at(tangential) thiab a (ib txwm) tso cai rau peb sau cov lus qhia rau kev txiav txim siab tag nrho acceleration module:
a=√(at2+ a2)
Rectilinear nrawm nrawm
Yog tias txoj kev taug yog txoj kab ncaj nraim, ces qhov nrawm nrawm tsis hloov thaum lub cev txav mus los. Qhov no txhais tau hais tias thaum piav tag nrho acceleration, ib tug yuav tsum paub tsuas yog nws tangential tivthaiv at. Qhov ib txwm muaj yuav yog xoom. Yog li, cov lus piav qhia ntawm kev nrawm nrawm hauv txoj kab ncaj nraim yog txo rau cov qauv:
a=at=dv/dt.
Los ntawm qhov kev qhia no tag nrho cov qauv kinematic ntawm rectilinear uniformly nrawm lossis sib npaug qeeb ua raws. Cia wb sau cia:
v=v0±at;
S=v0t ± at2/2.
Ntawm no cov cim ntxiv sib raug rau kev nrawm nrawm, thiab kos npe rho tawm kom qeeb zog (braking).
Uniform ncig txav
Tam sim no cia peb xav txog yuav ua li cas qhov nrawm thiab nrawm muaj feem cuam tshuam rau hauv rooj plaub ntawm kev sib hloov ntawm lub cev nyob ib ncig ntawm axis. Cia peb xav tias qhov kev sib hloov no tshwm sim ntawm qhov tsis tu ncua angular tshaj tawm ω, uas yog, lub cev tig los ntawm cov ces kaum sib npaug hauv lub sijhawm sib npaug. Raws li cov xwm txheej tau piav qhia, qhov linear tshaj tawm v tsis hloov nws tus nqi kiag li, tab sis nws cov vector hloov tas li. Qhov tseeb kawg piav txog kev nrawm li qub.
Tus qauv rau kev nrawm ib txwm a tau muab rau saum toj no. Cia wb sau dua:
a=v2/r
Qhov kev sib npaug no qhia tau tias, tsis zoo li cov khoom sib xyaw at, tus nqi a tsis sib npaug rau xoom txawm tias nyob ntawm qhov nrawm nrawm v. Qhov loj dua qhov modulus, thiab qhov me me ntawm lub vojvoog ntawm curvature r, qhov ntau dua tus nqi ntawm a . Cov tsos ntawm ib txwm acceleration yog vim qhov kev txiav txim ntawm lub centripetal quab yuam, uas nyhav kom lub cev rotating ntawm lub voj voog kab.
