10 Piv txwv ntawm kev txav mus los uas nrawm sib npaug
1. Thaum xub thawj lub tsheb nres. Tom qab 10 vib nas this, lub tsheb qhov ceev nce mus txog 20 m/s. Txheeb xyuas seb lub tsheb qhov kev nrawm npaum li cas!
Kev Sib Tham
Tsis muaj tus qauv (siv logic) :
Lub tsheb qhov ceev hloov mus rau 20 m/s tom qab 10 vib nas this. Qhov no txhais tau tias lub tsheb qhov ceev nce 2 m/s txhua ob vib nas this. Yog li, lub tsheb qhov kev nrawm yog 2 m/s ib ob = 2 m/s ib ob = 2 m/s2.
Siv cov mis :
Nws paub tias:
Qhov ceev pib (vo) = 0 (lub tsheb nres twj ywm)
Lub sijhawm luv (t) = 10 vib nas this
Qhov ceev kawg (vt) = 20 m/s
Nug: kev ua kom lub tsheb nrawm dua (a)
Lus teb:
Vim nws yog paub vonyob rau hauvt, t thiab nug ib ces siv tus qauv GLBB vt = vo + at
vt = vo + ntawm
20 = 0 + (a)(10)
20 = 10 ib
ib = 20 / 10
ib = 2 m/s2
Qhov loj ntawm lub tsheb qhov kev nrawm yog 2 m / s2Qhov no txhais tau tias lub tsheb qhov ceev nce ntxiv 2 m/s txhua 1 vib nas this.
2. Lub tsheb pib txav mus rau qhov ceev ntawm 30 m/s thiab txo nws qhov ceev kom txog thaum nws nres tom qab 10 vib nas this. Qhov loj ntawm lub tsheb qeeb qeeb yog...
Kev Sib Tham
Tsis muaj tus qauv (siv logic):
Lub tsheb qhov ceev txo qis ntawm 30 m/s mus rau 0 m/s hauv 10 vib nas this. Qhov no txhais tau tias lub tsheb qhov ceev txo qis 3 m/s txhua ob. Yog li, lub tsheb qhov kev qeeb yog 2 m/s ib ob = 3 m/s.2.
Siv cov mis:
Nws paub tias:
Qhov ceev pib (vo) = 30 m/s
Qhov ceev kawg (vt= 0 TZS
Lub sijhawm luv (t) = 10 vib nas this
Nug: kev qeeb (a)?
Lus teb:
Vim nws yog paub vonyob rau hauvt, t thiab nug ib ces siv tus qauv GLBB vt = vo + at
vt = vo + ntawm
0 = 30 + (a)(10)
– 30 = 10 ib
ib = – 30 / 10
ib = 3 m/s2
Qhov loj ntawm lub tsheb qhov kev nrawm yog -3 m / s2Qhov no txhais tau tias lub tsheb qhov ceev txo qis 3 m/s txhua ob. Lub cim tsis zoo qhia tias lub tsheb qhov ceev txo qis.
3. Ib yam khoom uas thaum xub thawj so, nws txav mus los nrog qhov nrawm tas li ntawm 4 m/s.2Txheeb xyuas qhov ceev thiab qhov deb uas taug kev tom qab 10 vib nas this.
Kev Sib Tham
(a) Ceev
Kev nrawm 4 m/s2 Qhov no txhais tau tias qhov ceev ntawm yam khoom nce 4 m/s txhua 1 vib nas this. Tom qab 2 vib nas this, qhov ceev ntawm yam khoom nce mus ua 8 m/s. Tom qab 10 vib nas this, qhov ceev ntawm yam khoom nce mus ua 40 m/s.
(b) Qhov deb uas tau mus
Qhov ceev pib (vo= 0 TZS
Qhov ceev kawg (vt) = 40 m/s
ib = 4 m/s2
Mais:
s = vo t + ½ ntawm2 = 0 + ½ (4)(10)2) = (2)(100) = 200 meters
4. Ib yam khoom uas txav mus los ntawm qhov ceev tas li ntawm 10 m/s thaum xub thawj yuav qeeb zuj zus li ntawm 2 m/s.2 kom txog thaum nws nres. Txheeb xyuas lub sijhawm thiab qhov deb uas lub tsheb mus ua ntej nres.
Kev Sib Tham
Nws paub tias:
Qhov ceev pib (vo) = 10 m/s
Kev nrawm (a) = -2 m/s2 (yog tias nws qeeb qeeb ces nws tau muab lub cim tsis zoo)
Qhov ceev kawg (vt) = 0 (khoom tsis txav mus los)
Lo lus nug: lub sijhawm thiab qhov deb uas tau mus ua ntej lub tsheb nres.
Lus teb:
(a) Lub sijhawm luv
Vim nws yog paub vonyob rau hauvt, a thiab nug t ces siv tus qauv GLBB vt = vo + ntawm
vt = vo + ntawm
0 = 10 + (-2)(t)
0 = 10 – 2 t
10 = 2 t
t = 10 / 2 = 5 vib nas this
Lub sijhawm ua ntej nres = 5 vib nas this.
(b) Qhov deb uas tau mus
vt2 = vo2 + 2 lub qag
0 = 102 + 2(-2) vib nas this
0 = 100 – 4 vib nas this
100 = 4 vib nas this
s = 100 / 4 = 25 meters
Qhov deb uas lub tsheb tau mus ua ntej nres yog 25 meters
5. Lub tsheb uas khiav ceev li 40 m/s thaum xub thawj yuav qeeb qeeb li 4 m/s.2. Txheeb xyuas qhov ceev thiab qhov deb uas lub tsheb tau mus tom qab qeeb qeeb li 10 vib nas this.
Kev Sib Tham
Nws paub tias:
Qhov ceev pib (vo) = 40 m/s
Kev nrawm (a) = -4 m/s2
Lub sijhawm luv (t) = 10 vib nas this
Nug: qhov ceev (v)t) thiab qhov deb (s) tom qab deceleration rau 10 vib nas this
Lus teb:
(a) Qhov ceev kawg
vt = vo + ntawm = 40 + (-4)(10) = 40 – 40 = 0 m/s
Tom qab qeeb qeeb li 10 vib nas this, qhov ceev ntawm lub tsheb hloov mus rau 0 lossis lub tsheb nres.
(b) Qhov deb uas tau mus
s = vo t + ½ ntawm2 = (40)(10) + ½ (-4)(10)2) = 400 + (-2)(100) = 400 – 200 = 200 meters
Qhov deb uas lub tsheb mus tom qab qeeb qeeb li 10 vib nas this kom txog thaum nws nres yog 200 meters.
6. Qhov ceev (v) ntawm ib yam khoom uas txav mus rau hauv ib txoj kab ncaj nraim tawm tsam lub sijhawm (t) yog raws li pom hauv daim duab v-t. Qhov deb uas yam khoom taug kev hauv 5 vib nas this yog…
Kev Sib Tham
Qhov deb uas tau mus (s) = vt = (10-0)(5-0) = (10)(5) = 50 meters
7. Daim duab ntawm sab qhia txog kev txav ntawm lub tsheb mus rau hauv ib txoj kab ncaj nraim nrog qhov nrawm tas li. Qhov deb uas lub tsheb taug kev hauv 4 vib nas this yog….
Kev Sib Tham
Qhov deb mus ncig = thaj tsam ntawm lub xwmfab + thaj tsam ntawm daim duab peb sab
Kev nrug deb = (8-0)(8-0) + ½ (16-8)(8-0) = (8)(8) + ½ (8)(8) = 64 + 32 = 96 meters
8. Daim duab ntawm sab qhia txog lub tsheb khiav ncaj nraim nrog qhov ceev tas li. Qhov deb uas lub tsheb khiav hauv 4 vib nas this yog….
Kev Sib Tham
Qhov deb mus ncig = thaj tsam ntawm daim duab peb sab = ½ (4-0)(8-0) = ½ (4)(8) = 16 meters
9. Saib daim ntawv teev lus hauv qab no!
Lub rooj saum toj no qhia peb yam khoom txav mus rau hauv ib txoj kab ncaj nraim ntawm qhov nrawm tas li uas npog tib qhov deb. Qhov ceev kawg P thiab qhov ceev pib Q ntawm cov khoom yog….
A. 20 ms -1 thiab 20 ms -1
B. 20 ms -1 thiab 28 ms -1
C. 20 ms -1 thiab 40 ms -1
D. 40 ms -1 thiab 20 ms -1
E. 40 ms -1 thiab 40 ms -1
Kev Sib Tham
Qhov deb uas tau mus los zoo ib yam, yog li ntawd xub xam qhov deb uas tus khoom lej 3 tau mus los ua ntej.
Qhov deb uas tus lej 3 tau mus ncig:
Nws paub tias:
Qhov ceev pib ( v₂o ) = 0 m/s
Qhov ceev kawg (v t ) = 30 m/s
Kev nrawm (a) = 3 m/s 2
Nug : Qhov Deb
Lus teb:
vt2 = vo2 + 2 as
v t 2 – v o 2 = 2 as
30 2 – 0 2 = 2 (3) vib nas this
900 – 0 = 6 vib nas this
900 = 6 vib nas this
s = 900 / 6
s = 150 meters
Qhov ceev kawg ntawm yam khoom naj npawb 1:
Nws paub tias:
Qhov ceev pib ( v₂o ) = 20 m/s
Kev nrawm (a) = 4 m/s 2
Qhov Nrug Deb (s) = 150 meters
Lo lus nug : Qhov ceev kawg (v t )
Lus teb:
vt2 = vo2 + 2 as
v t 2 = 20 2 + 2 (4)(150)
vt2 = 400 + 1200
vt2 = 1600
vt = 40 m/s
Qhov ceev pib ntawm yam khoom naj npawb 2:
Nws paub tias:
Qhov ceev kawg (v t ) = 50 m/s
Kev nrawm (a) = 3 m/s 2
Qhov Nrug Deb (s) = 150 meters
Lus Nug : Qhov ceev pib (v o )
Lus teb:
vt2 = vo2 + 2 as
v t 2 – 2 as = v o 2
50 2 – 2(3)(150) = v2
2500 – 900 = v2
1600 = v2
v₂o = 40 m/s
Cov lus teb yog yog E.
10. Peb yam khoom txav mus rau hauv ib txoj kab ncaj nraim ntawm qhov nrawm tas li ntawm ib qho chaw tiaj tus. Tag nrho peb yam khoom txav mus nrog tib qhov kev nrawm. Qhov loj ntawm peb yam khoom tom qab txav mus rau 10 vib nas this tau qhia nyob rau hauv cov lus hauv qab no:
Cov ntaub ntawv P thiab Q hauv lub rooj muaj tus nqi….
A. 6 thiab 140
B. 6 thiab 120
C. 4 thiab 120
D. 4 thiab 100
E. 1 thiab 100
Kev Sib Tham
Qhov kev nrawm ntawm peb yam khoom yog tib yam, yog li ntawd xub xam qhov kev nrawm ntawm yam khoom 1.
Kev nrawm ntawm yam khoom 1:
Nws paub tias:
Qhov ceev pib ( v₂o ) = 2 m/s
Qhov ceev kawg (v t ) = 22 m/s
Qhov Nrug Deb (s) = 120 meters
Nug : Qhov Deb
Lus teb:
vt2 = vo2 + 2 as
v t 2 – v o 2 = 2 as
22 2 – 2 2 = 2 ib (120)
484 – 4 = 240 a
480 = 240 ib
ib = 480/240
a = 2 m/s 2
Qhov ceev pib ntawm yam khoom 2:
Nws paub tias:
Kev nrawm (a) = 2 m/s 2
Qhov ceev kawg (v t ) = 24 m/s
Qhov Nrug Deb (s) = 140 meters
Lus Nug : Qhov ceev pib (v o )
Lus teb:
vt2 = vo2 + 2 as
24 2 = vo 2 + 2 (2)(140)
576 = v2 + 560
576 – 560 = v2
16 = v2
v₂o = 4 m/s
Qhov nrug ntawm yam khoom 3:
Nws paub tias:
Qhov ceev pib ( v₂o ) = 0 m/s
Qhov ceev kawg (v t ) = 20 m/s
Kev nrawm (a) = 2 m/s 2
Nug : Qhov Deb ( s )
Lus teb:
vt2 = vo2 + 2 as
20 2 = 0 2 + 2 (2) vib nas this
20 2 = 2 (2) vib nas this
400 = 4 vib nas this
s = 400/4
s = 100 meters
Cov lus teb yog D.
Cov lus nug txog kev txav mus los uas nrawm sib npaug
1. Thaum xub thawj lub tsheb nres. Tom qab 5 vib nas this, lub tsheb qhov ceev nce mus txog 15 m/s. Txheeb xyuas seb lub tsheb qhov kev nrawm npaum li cas!
2. Lub tsheb pib txav mus rau qhov ceev ntawm 24 m/s thiab txo nws qhov ceev kom txog thaum nws nres tom qab 3 vib nas this. Qhov loj ntawm lub tsheb qeeb qeeb yog...
3. Ib yam khoom uas thaum xub thawj so, nws txav mus los nrog qhov nrawm tas li ntawm 5 m/s.2Txheeb xyuas qhov ceev thiab qhov deb uas taug kev tom qab 10 vib nas this.
4. Ib yam khoom uas txav mus los ntawm qhov ceev tas li ntawm 5 m/s thaum xub thawj yuav qeeb zuj zus li ntawm 5 m/s.2 kom txog thaum nws nres. Txheeb xyuas lub sijhawm thiab qhov deb uas lub tsheb mus ua ntej nres.
5. Lub tsheb uas khiav ceev li 30 m/s thaum xub thawj yuav qeeb qeeb li 5 m/s.2. Txheeb xyuas qhov ceev thiab qhov deb uas lub tsheb tau mus tom qab qeeb qeeb li 5 vib nas this.
6. Qhov ceev (v) ntawm ib yam khoom uas txav mus rau hauv ib txoj kab ncaj nraim tawm tsam lub sijhawm (t) yog raws li pom hauv daim duab v-t. Qhov deb uas yam khoom taug kev hauv 10 vib nas this yog…
7. Daim duab ntawm sab qhia txog kev txav ntawm lub tsheb mus rau hauv ib txoj kab ncaj nraim nrog qhov nrawm tas li. Qhov deb uas lub tsheb taug kev hauv 4 vib nas this yog….
8. Daim duab ntawm sab qhia txog lub tsheb khiav ncaj nraim nrog qhov ceev tas li. Qhov deb uas lub tsheb khiav hauv 4 vib nas this yog….
[Lus Askiv: Kev nrawm tas li - teeb meem thiab kev daws teeb meem ]
