Kev sib tsoo zoo kawg nkaus elastic
Kev sib tsoo ntawm ob yam khoom hu ua kev sib tsoo zoo kawg nkaus yog tias lub zog lossis lub zog kinetic ntawm txhua yam khoom ua ntej kev sib tsoo sib npaug rau lub zog thiab lub zog kinetic ntawm txhua yam khoom tom qab kev sib tsoo. Hauv lwm lo lus, kev txuag txoj cai momentum thiab kev txuag txoj cai kinetic zog siv tau rau hauv kev sib tsoo zoo kawg nkaus. Kev siv lo lus elastic qhia tias tom qab kev sib tsoo, ob yam khoom tsis lo ua ke lossis tsis txuas rau ib leeg tab sis dhia tawm. Lub zog ntawm txhua yam khoom raug khaws cia.
Lub zog ntawm txhua yam khoom raug khaws cia.
m1 v1 +m2 v2 = kuv1 v1 ' + m2 v2 ' ……………….. Kab zauv 1.5
Lub zog kinetic ntawm txhua yam khoom raug khaws cia.
1/2 mv12 + 1/2 mv22 = 1/2 mv1'2 + 1/2 mv2'2 ……………….. Kab zauv 1.6
Qhov kev sib tsoo uas zoo kawg nkaus elastic yuav tsum ntsiag to thiab tsis tsim cua sov vim muaj kev sib txhuam ntawm ob yam khoom sib tsoo. Yog tias qhov kev sib tsoo ntawm ob yam khoom tsim suab nrov thiab cua sov, lub zog kinetic ntawm cov khoom tsis raug khaws cia. Qee lub zog kinetic raug hloov mus ua lub zog suab thiab lub zog cua sov, thiab qee qhov raug hloov mus ua lub zog sab hauv. Ib qho piv txwv ntawm kev sib tsoo uas zoo kawg nkaus elastic yog qhov kev sib tsoo ntawm cov khoom me me atomic thiab subatomic.
Hauv qhov teeb meem ntawm kev sib tsoo zoo kawg nkaus, yog tias qhov ceev pib paub thaum qhov ceev kawg tsis paub, qhov teeb meem tsis tuaj yeem daws tau los ntawm kev siv cov qauv 1.5 thiab 1.6 xwb. Vim li no, ob qho tib si ntawm cov qauv no raug tswj hwm los muab lwm cov qauv, uas tuaj yeem siv los txiav txim siab qhov ceev kawg.
Tshem tawm qhov tseem ceeb 1/2 ces tswj 1.6
m1 v12 +m2 v22 = kuv1 v1 ' 2 +m2 v2 ' 2
m1 v12 -m1 v1' 2 = kuv2 v2 ' 2 -m2 v22
m1 (v12 -v1' 2 ) = m2 (v2 ' 2 - v2 2) —> (a + b)(a – b) = a2 - b2
m1 (v1 +v1 ') (v1 -v1 ') = m2 (v2 ' + v2 ) (v2 ' – v2 ) …………………….. Kab zauv 1.7
Tswj cov kab zauv 1.5
m1 v1 -m1 v1 ' = m2 v2 '-m2 v2
m1 (v1 -v1 ') = m2 (v2 ' – v2) …………………….. Kab zauv 1.8
Faib kab zauv 1.7 los ntawm kab zauv 1.8 kom tau txais qhov tshwm sim kawg
(v1 +v1 ') = (v2 ' + v2)
v1 -v2 = v2 ' – v1 '
v1 -v2 = – (v)1 ' – v2 ') …………….. Kab zauv 1.9
Cov qauv 1.5 thiab 1.9 siv tau los daws cov teeb meem ntawm kev sib tsoo zoo kawg nkaus. Muab cov qauv 1.5 thiab 1.9 ua ke kom tau ob qho qauv rau kev txiav txim siab qhov ceev kawg ntawm ob yam khoom yog tias lawv cov pawg thiab qhov ceev pib tsis paub.
Thaum daws cov lus nug siv cov qauv saum toj no, siv lub cim raug rau v1 thiab v2Yog tias yam khoom 1 txav mus rau sab xis, v1 yog qhov zoo, thiab rov qab, yog tias object ob txav mus rau sab laug, v2 yog tsis zoo. Yog tias ob yam khoom txav mus rau hauv cov kev taw qhia sib txawv, tab sis tsis muaj cov ntaub ntawv hais txog cov kev taw qhia kev txav mus los, v1 thiab v2 yuav tsum tau kos npe txawv, piv txwv li, v1 yog qhov zoo, thiab v2 yog qhov tsis zoo.
4.1.1 Ob yam khoom uas muaj tib lub cev hnyav
Yog tias m1 = kuv2nyob rau hauv1 ' = v2 thiab v2' = v1 .
Yuav ua li cas yog tias ob yam khoom txav mus rau hauv cov kev taw qhia sib txawv?
Piv txwv li, yog tias ua ntej sib tsoo khoom 1 txav mus rau sab xis thiab khoom 2 txav mus rau sab laug, khoom 1 yuav txav mus rau sab laug (v1' = – v2) thiab yam khoom 2 yuav txav mus rau sab xis (v2' = v1) tom qab kev sib tsoo.
Yuav ua li cas yog tias ib qho ntawm cov khoom thaum xub thawj so?
Piv txwv li, yog tias ua ntej kev sib tsoo khoom 2 nyob twj ywm (v2 = 0), yam khoom 1 yuav so (v)1' = 0) thiab yam khoom 2 yuav txav mus rau tib qhov ceev li qhov ceev pib ntawm yam khoom 1 (v2' = v1) tom qab sib tsoo. Yog tias ua ntej kev sib tsoo khoom 1 txav mus rau sab xis, khoom 2 yuav txav mus rau sab xis tom qab kev sib tsoo. Yog li ntawd, ob yam khoom sib pauv qhov ceev.
Piv txwv lo lus nug 4
Cov khoom A (2 kg) thiab B (2 kg) txav mus rau qhov sib txawv ntawm qhov ceev ntawm 4 m/s thiab 2 m/s, raws li. Yog tias cov khoom A thiab B sib tsoo hauv qhov kev sib tsoo zoo kawg nkaus, qhov ceev kawg ntawm cov khoom A thiab B yog dab tsi?
Paub:
mA = 2 kg, mB = 2 kg, vA = 4 m/s, vB = – 2 m/s
SE pob: vA'thiab vB '
Tshuaj:
vA' = – 2 m/s thiab vB' = 4 m/s
Tom qab kev sib tsoo, yam khoom A txav mus nrog qhov ceev ntawm 2 m/s thiab yam khoom B txav mus nrog qhov ceev ntawm 4 m/s mus rau sab nraud. Yog tias ua ntej kev sib tsoo yam khoom A txav mus rau sab xis thiab yam khoom B txav mus rau sab laug, yam khoom A yuav txav mus rau sab laug thiab yam khoom B yuav txav mus rau sab xis tom qab kev sib tsoo.
Piv txwv lo lus nug 5
Khoom A (2 kg) txav mus rau sab xis ntawm qhov ceev ntawm 2 m/s thiab sib tsoo nrog khoom B (2 kg) uas tsis txav. Yog tias ob yam khoom sib tsoo ua ib qho kev sib tsoo zoo kawg nkaus, qhov ceev kawg ntawm cov khoom A thiab B yog dab tsi?
Paub:
mA = 2 kg, mB = 2 kg, vA = 2 m/s, vB = 0 m/s
SE pob: vA 'thiab vB '
Tshuaj:
vA' = 0 thiab vB' = 2 m/s
Tom qab kev sib tsoo, yam khoom A nyob twj ywm, thiab yam khoom B txav mus rau sab xis ntawm qhov ceev ntawm 2 m/s.
4.1.2 Ob yam khoom uas muaj qhov hnyav sib txawv
Yog tias ob yam khoom muaj qhov ceev pib thiab qhov hnyav sib txawv (qhov sib txawv me me), qhov ceev kawg paub los ntawm kev siv cov qauv 1.10 thiab 1.11.
Yog tias thaum xub thawj yam khoom 2 nyob twj ywm (v2 = 0), kab zauv 1.10 dhau los ua kab zauv 1.12 thiab kab zauv 1.11 dhau los ua kab zauv 1.13.
Yog tias v2 = 0, m1 zoo heev thiab m2 me me heev, los ntawm kev daws cov kab zauv 1.12 thiab 1.13 v1' = v1 thiab v2' = 2v1 tau txais. Yog tias v2 = 0, m1 me me heev, thiab m2 zoo heev, los ntawm kev daws cov kab zauv 1.12 thiab 1.13 v1 ' = -v1 thiab v2 ' = 0 tau txais. Cov cim zoo thiab tsis zoo qhia txog kev txav mus los sib txawv.
Piv txwv lo lus nug 6
Ib yam khoom uas hnyav 1 kg txav mus los ntawm qhov ceev ntawm 20 m/s thiab sib tsoo nrog phab ntsa hauv qhov kev sib tsoo zoo kawg nkaus elastic. Qhov ceev kawg ntawm yam khoom thiab phab ntsa yog dab tsi?
Paub:
mA = 1 kg, vA = 20 m/s, mB = zoo heev, vB = 0
xav : nyob rau hauvA'thiab vB'
Tshuaj:
vA' = -20 m/s thiab vB' = 0
Tom qab sib tsoo, yam khoom A dhia tawm ntawm qhov ceev ntawm 20 m/s thiab yam khoom B tseem nyob twj ywm. Yog tias ua ntej sib tsoo yam khoom A txav mus rau sab xis, nws txav mus rau sab laug tom qab sib tsoo.
