14 Piv txwv ntawm Cov Lus Nug Txog Particle Dynamics
1. Lub thaiv A uas hnyav 5 kg muab tso rau ntawm ib qho chaw tiaj tiaj, lub thaiv B uas hnyav 3 kg muab dai nrog ib txoj hlua thiab txuas rau lub thaiv A ntawm lub pulley, yog tias g = 10 m/s 2 txiav txim siab qhov kev nrawm ntawm lub thaiv!
A. 3,50 m/s2
B. 3,75 m/s 2
C. 4,00 m/s 2
D. 5,00 m/s 2
E. 5,25 m/s 2
Kev Sib Tham
Nws paub tias:
Qhov chaw tiaj tiaj.
Qhov hnyav ntawm lub thaiv A (m A ) = 5 kg
Qhov hnyav ntawm thaiv B (mB ) = 3 kg
Kev nrawm vim lub ntiajteb txawj nqus (g) = 10 m/s 2
Qhov hnyav ntawm thaiv B (w B ) = m B g = (3)(10) = 30 Newton
Lo lus nug: Kev ua kom nrawm ntawm lub block (a)
Lus teb:
Qhov chaw tiaj tiaj yog du yog li ntawd tsis muaj lub zog sib txhuam uas cuam tshuam kev txav ntawm lub thaiv A. Lub zog uas txav lub kaw lus thaiv yog qhov hnyav ntawm lub thaiv B.
ΣF = ma
w B = (m A + m B ) a
30 = (5 + 3) ib
30 = 8 ib
ib = 30 / 8
a = 3,75 m/s 2
Cov lus teb yog B.
2. Raws li daim duab, nws paub tias:
(1) qhov kev nrawm ntawm qhov khoom xoom
(2) cov khoom txav mus rau hauv ib txoj kab ncaj nraim ntawm qhov ceev tas li
(3) cov khoom nyob rau hauv lub xeev so
(4) ib yam khoom yuav txav mus yog tias qhov hnyav ntawm yam khoom tsawg dua lub zog rub
Cov lus hais tseeb yog….
A. (1) thiab (2) xwb
B. (1) thiab (3) xwb
C. (1) thiab (4)
D. (1), (2) thiab (3) xwb
E. (1), (2), (3) thiab (4)
Kev Sib Tham
(1) qhov kev nrawm ntawm qhov khoom xoom
Qhov kev nrawm ntawm ib yam khoom yog xoom yog tias lub zog tshwm sim sib npaug rau xoom. Lub zog tshwm sim:
∑F = ma 
kev nrawm (a) = 0
∑ F = 0
F 1 + F 2 – F 3 = 12 + 24 – 36 = 36 – 36 = 0 N
(2) cov khoom txav mus rau hauv ib txoj kab ncaj nraim ntawm qhov ceev tas li
Qhov kev nrawm ntawm ib yam khoom xoom txhais tau tias yam khoom ntawd nyob twj ywm lossis yam khoom ntawd txav mus rau hauv ib txoj kab ncaj nraim ntawm qhov ceev tas li (yam khoom ntawd txav mus rau qhov ceev tas li).
(3) cov khoom nyob rau hauv lub xeev so
Lub zog ntawm xoom txhais tau tias qhov khoom ntawd so.
(4) ib yam khoom yuav txav mus yog tias qhov hnyav ntawm yam khoom tsawg dua lub zog rub
Qhov hnyav ntawm ib yam khoom ua haujlwm ntsug, thaum lub zog tensile ua haujlwm kab rov tav. Vim tias yam khoom txav mus kab rov tav, tsuas yog lub zog kab rov tav xwb thiaj cuam tshuam rau yam khoom.
Cov lus teb yog D.
3. Saib daim duab ntawm sab!
Yog tias tus coefficient ntawm kinetic friction ntawm block A thiab lub rooj yog 0,1 thiab qhov acceleration vim gravity yog 10 m/s-2 ces lub zog uas yuav tsum tau siv rau A kom lub cev txav mus rau sab laug nrog kev nrawm
n 2 ms-2 yog ....
A. 70 N
B. 90 N
C. 150 N
D. 250 N
Sab Hnub Tuaj 330 N
Kev Sib Tham
Nws paub tias:
Qhov hnyav ntawm lub thaiv A (m A ) = 30 kg
Qhov hnyav ntawm thaiv A (w A ) = (30 kg)(10 m/s 2 ) = 300 kg m/s 2 lossis 300 Newton
Qhov hnyav ntawm thaiv B (mB ) = 20 kg
Qhov hnyav ntawm thaiv B (w B ) = (20 kg)(10 m/s 2 ) = 200 kg m/s2 lossis 200 Newtons
Kev nrawm vim lub ntiajteb txawj nqus (g) = 10 m/s 2
Coefficient ntawm kev sib txhuam kinetic (
= 0,1 TZS
Kev nrawm ntawm lub kaw lus (a) = 2 m/s 2 (kev taw qhia ntawm kev nrawm mus rau sab laug)
Lub zog sib txhuam Kinetic (f)k) = Tsis yog = wA = (0,1)(300) = 30 Newtons
Lus Nug: Lub zog F yog dab tsi?
Lus teb:
Txoj Cai Thib Ob ntawm Newton:
Σ F = ma
Lub kaw lus txav mus rau sab laug
F – fk – w B = (m A + m B ) a
F – 30 – 200 = (30 + 20)(2)
F – 230 = (50)(2)
F – 230 = 100
F = 230 + 100
F = 330 Newtons
Cov lus teb yog yog E.
4. Ob yam khoom A thiab B, uas hnyav 2 kg thiab 6 kg, raug khi nrog ib txoj hlua los ntawm lub pulley du raws li pom hauv daim duab. Ua ntej, yam khoom B raug tuav thiab tom qab ntawd tso tawm. Yog tias g = 10 ms -2 ces qhov kev nrawm ntawm yam khoom B yog...
A. 8,0 ms-2
B. 7,5 ms -2
C. 6,0 ms -2
D. 5,0 ms -2
E. 4,0 ms -2
Kev Sib Tham
Nws paub tias:
m A = 2 kg, m B = 6 kg, g = 10 m/s 2
w A = (m A )(g) = (2)(10) = 20 N
w B = (mB ) (g) = (6)(10) = 60 N
Lo lus nug: kev ua kom nrawm ntawm yam khoom B lossis kev ua kom nrawm ntawm lub kaw lus?
Lus teb:
w B > w A yog li ntawd yam khoom B txav mus rau hauv qab, yam khoom A txav mus rau saum toj (lub kaw lus txav mus rau sab laug).
Σ F = ma
w B – w A = (m A + m B ) a
60 – 20 = (2 + 6) ib
40 = (8) ib
a = 5 m/s 2
Cov lus teb yog D.
5. Ib yam khoom uas muaj qhov hnyav sib txuas los ntawm ib txoj hlua hla lub pulley du raws li pom hauv daim duab. Yog tias m 1 = 1 kg, m 2 = 2 kg, thiab g = 10 ms -2 , ces qhov nro T yog ....
A. 10,2 N 
B. 13,3 N
C. 15,5 N
D. 18,3 N
Sab Hnub Tuaj 20,0 N
Kev Sib Tham
Nws paub tias:
m 1 = 1 kg, m 2 = 2 kg, g = 10 m/s 2
w 1 = m 1 g = (1 kg)(10 m/s 2 ) = 10 kg m/s 2 los yog 10 Newtons
w 2 = m 2 g = (2 kg)(10 m/s 2 ) = 20 kg m/s 2 los yog 20 Newtons
Lus Nug: Lub zog nruj ntawm txoj hlua (T) yog dab tsi?
Lus teb:
Kev ua kom lub kaw lus nrawm dua
w 2 > w 1 yog li ntawd lub kaw lus txav mus rau sab laug (m 2 txav mus rau hauv qab, m 1 txav mus rau saum toj).
Txoj Cai Thib Ob ntawm Newton:
Σ F = ma
w 2 – w 1 = (m 1 + m 2 ) a
20 – 10 = (1 + 2) ib
10 = (3) ib
a = 3,3 m/s 2
Qhov kev nrawm ntawm lub kaw lus yog 3,3 m / s2.
Txoj hlua nruj?
m 2 txav mus rau hauv qab
w 2 – T 2 = m 2 a
20 – T 2 = (2)(3,33)
20 – T 2 = 6,66
T 2 = 20 – 6,66
T 2 = 13,3 Newtons
m 1 txav mus rau saum toj
T 1 – w 1 = m 1 a
T 1 – 10 = (1)(3,3)
T 1 – 10 = 3,33
T 1 = 10 + 3,33
T 1 = 13,3 Newtons
Lub zog ntawm txoj hlua (T) = 13,3 Newtons.
Cov lus teb yog B.
6. Saib daim duab ntawm sab! Qhov hnyav ntawm cov blocks yog m 1 = 6 kg thiab m 2 = 4 kg, thiab qhov hnyav ntawm lub pulley raug tsis quav ntsej. Yog tias qhov chaw ntawm lub dav hlau du thiab g = 10 m s −2 , ces qhov kev nrawm ntawm lub system yog….
A. 0,5 ms-2
B. 2,0 ms −2
C. 2,5 ms −2
D. 4,0 ms −2
E. 5,0 ms −2
Kev Sib Tham
Nws paub tias:
m1 = 6 kg, m2 = 4 kg, g = 10 m/ s2
w 1 = m 1 g = (6 kg)(10 m/s 2 ) = 60 kg m/s 2 los yog 60 Newtons
w 2 = m 2 g = (4 kg)(10 m/s 2 ) = 40 kg m/s 2 los yog 40 Newtons
Nug: kev ua kom lub kaw lus nrawm dua (a)?
Lus teb:
m 1 nyob rau ntawm ib qho chaw du thiab tsis muaj kev sib txhuam kom lub kaw lus raug tsav los ntawm lub zog gravitational ntawm block 2.
Siv txoj cai thib ob ntawm Newton:
∑ F = ma
w 2 = (m 1 + m 2 ) a
40 N = (6 kg + 4 kg) ib
40 N = (10 kg) ib
a = 40 N / 10 kg
a = 4 m/s 2
Cov lus teb yog D.
7. Ob lub thaiv, txhua lub muaj qhov hnyav 2 kg, txuas nrog ib txoj hlua thiab lub pulley raws li pom hauv daim duab. Qhov saum npoo thiab lub pulley du. Yog tias lub thaiv B raug rub nrog lub zog kab rov tav ntawm 40 N, qhov kev nrawm ntawm lub thaiv yog ... (g = 10 m / s 2 )
A. 5 m/s2
B. 7,5 m/s 2
C. 10 m/s 2
D. 12,5 m/s 2
E. 15 m/s 2
Kev Sib Tham:
Nws paub tias:
m A = m B = 2 kg, g = 10 m/s 2 , F = 40 N
w A = mg = (2)(10) = 20 N
Lo lus nug: kev ua kom nrawm ntawm lub thaiv (a)?
Lus teb:
Qhov saum npoo ntawm lub thaiv yog du, yog li ntawd cov zog uas cuam tshuam rau kev txav mus los ntawm lub thaiv tsuas yog lub zog F thiab qhov hnyav ntawm lub thaiv A.
Siv txoj cai thib ob ntawm Newton:
∑ F = ma
F – w A = (m A + m B ) a
40 – 20 = (2 + 2) ib
20 = (4) ib
ib = 20 / 4
a = 5 m/s 2
Cov lus teb yog lawm yog A.
8. Los ntawm daim duab hauv qab no, thaiv A muaj qhov hnyav ntawm 2 kg thiab thaiv B = 1 kg. Thaiv B pib tsis txav thiab tom qab ntawd txav mus rau hauv qab kom txog thaum nws kov hauv pem teb. Yog tias g = 10 ms -2 , tus nqi ntawm qhov nro hauv txoj hlua T yog...
A. 20,0 Newtons
B. 10,0 Newton
C. 6,7 Newton
D. 3,3 Newton
E. 1,7 Newtons
Kev Sib Tham
Nws yog paub tias :
Qhov hnyav ntawm lub thaiv A (m A ) = 2 kg
Qhov hnyav ntawm thaiv B (mB ) = 1 kg
Kev nrawm vim lub ntiajteb txawj nqus (g) = 10 m/s 2
Qhov hnyav ntawm thaiv B (w B ) = m B g = (1)(10) = 10 Newton
Lus Nug : Tus nqi ntawm txoj hlua khi (T)
Lus teb :
Hauv lo lus nug tsis muaj cov ntaub ntawv hais txog kev sib txhuam, yog li tsuas yog tsis quav ntsej txog kev sib txhuam.
Kev ua kom lub kaw lus nrawm dua (a)
Ua ntej, xam qhov kev nrawm ntawm lub kaw lus siv Newton txoj cai thib ob. Block B raug dai kom muaj lub zog ntawm block B lub ntiajteb txawj nqus uas txav block B mus rau hauv qab. Block B thiab block A txuas nrog txoj hlua kom block B rub block A kom txog thaum lawv ob leeg txav ua ke. Qhov sib txawv yog tias block B txav mus rau hauv qab thiab block A txav mus rau sab xis. Tsuas muaj ib lub zog sib luag rau kev txav ntawm ob lub blocks, uas yog lub ntiajteb txawj nqus ntawm block B (wB). Lub ntiajteb txawj nqus ntawm block A yog perpendicular rau qhov kev taw qhia ntawm block A txav mus los yog li nws tsis raug coj los xav txog hauv kev daws qhov teeb meem. Lub zog nruj ntawm txoj hlua muaj tib qhov loj ntawm txoj hlua thiab cov lus qhia sib txawv kom lawv tshem tawm ib leeg.
∑ F = ma
w B = (m A + m B ) a
10 = (2 + 1) ib
10 = 3 ib
ib = 10/3
Kev nruj ntawm hlua (T)
Qhov kev nruj ntawm txoj hlua yog xam los ntawm kev xav txog txhua lub thaiv sib cais.
Qhov nro ntawm txoj hlua ntawm thaiv A
∑ F = ma
T = m A a = (2)(10/3) = 20/3 = 6,7 Newtons
Lub zog ntawm txoj hlua khi ntawm lub thaiv B
∑ F = ma
w B – T = m B a
10 – T = (1)(10/3)
10 – T = 3,3
T = 10 – 3,3 = 6,7 Newtons
Lub zog nruj ntawm txoj hlua (T) = 6,7 Newton
Cov lus teb yog C.
9. Los ntawm daim duab hauv qab no, thaiv A muaj qhov hnyav ntawm 2 kg thiab thaiv B = 1 kg. Yog tias lub zog sib txhuam ntawm yam khoom A thiab lub dav hlau yog 2,5 Newton, thaum lub zog sib txhuam ntawm txoj hlua thiab lub pulley tsis raug saib xyuas, ces qhov kev nrawm ntawm ob yam khoom yog...
A. 20,0 ms-2
B. 10,0 ms -2
C. 6,7 ms -2
D. 3,3 ms -2
E. 2,5 ms -2
Kev Sib Tham
Nws yog paub tias :
Qhov hnyav ntawm lub thaiv A (m A ) = 2 kg
Qhov hnyav ntawm thaiv B (mB ) = 1 kg
Lub zog sib txhuam ntawm thaiv A thiab ib qho chaw tiaj tus (f ges A ) = 2,5 Newton
Kev nrawm vim lub ntiajteb txawj nqus (g) = 10 m/s 2
Qhov hnyav ntawm thaiv B (w B ) = m B g = (1)(10) = 10 Newton
Lo lus nug : Kev nrawm ntawm ob yam khoom (a)
Lus teb :
Qhov kev nrawm ntawm ob yam khoom yog xam los ntawm kev siv Newton txoj cai thib ob.
∑ F = ma
w B – f ges = (m A + m B ) a
10 – 2,5 = (2 + 1) ib
7,5 = 3 ib
a = 7,5 / 3 = 2,5 m/s 2
Cov lus teb yog yog E.
10. Saib daim duab! Lub thaiv A uas muaj qhov hnyav 30 kg so rau hauv pem teb du yog txuas nrog lub thaiv B uas muaj qhov hnyav 10 kg ntawm lub pulley. Lub thaiv B raug tuav ua ntej thiab tom qab ntawd tso tawm kom nws txav mus rau hauv qab. Qhov kev nrawm ntawm lub kaw lus yog ... (g = 10 ms -2 )
A. 2,5 ms-2
B. 10 ms -2
C. 12 ms -2
D. 15 ms -2
E. 18 ms -2
Kev Sib Tham
Nws yog paub tias :
Qhov hnyav ntawm lub thaiv A (m A ) = 30 kg
Qhov hnyav ntawm thaiv B (mB ) = 10 kg
Kev nrawm vim lub ntiajteb txawj nqus (g) = 10 m/s 2
Qhov hnyav ntawm thaiv B (w B ) = m B g = (10)(10) = 100 Newton
Lo lus nug : Kev ua kom lub cev nrawm dua (a)
Lus teb :
∑ F = ma
w B = (m A + m B ) a
100 = (30 + 10) ib
100 = 40 ib
ib = 100 / 40
a = 2,5 m/s 2
Cov lus teb yog lawm yog A.
11. Cov Blocks A thiab B, txhua lub muaj qhov hnyav 8 kg thiab 12 kg, raug muab tso rau ntawm lub rooj raws li qhia hauv daim duab. Tus coefficient ntawm kev sib txhuam ntawm cov block A thiab lub rooj yog 0,3. Cov Block C, nrog qhov hnyav 4 kg, ces raug muab tso rau saum cov block A. Cov lus hauv qab no, cov lus twg yog qhov tseeb?
A. Qhov kev nruj ntawm txoj hlua ntau dua li ua ntej, qhov kev nrawm tsawg dua li ua ntej
B. Qhov kev nruj ntawm txoj hlua thiab qhov kev nrawm ntawm lub kaw lus tsis hloov pauv.
C. Qhov kev nruj ntawm txoj hlua me dua li ua ntej, qhov kev nrawm dua li ua ntej.
D. Qhov kev nruj ntawm txoj hlua yog ntau dua li ua ntej, qhov kev nrawm tseem ruaj khov.
E. Qhov kev nruj ntawm txoj hlua tseem ruaj khov thaum qhov kev nrawm me dua li ua ntej.
Kev Sib Tham
Nws paub tias:
Qhov hnyav ntawm lub thaiv A (m A ) = 8 kg
Qhov hnyav ntawm thaiv B (mB ) = 12 kg
Qhov hnyav ntawm thaiv C (mC ) = 4 kg
Tus coefficient ntawm kev sib txhuam ntawm thaiv A thiab lub rooj ( μ k ) = 0,3
Kev nrawm vim lub ntiajteb txawj nqus (g) = 10 m/s 2
Qhov hnyav ntawm thaiv A (w A ) = m A g = (8 kg) (10 m/s 2 ) = 80 kg m/s 2
Qhov hnyav ntawm thaiv B (w B ) = m B g = (12 kg) (10 m/s 2 ) = 120 kg m/s 2
Lub zog sib txhuam ntawm thaiv A thiab lub rooj (f k ) = μ k N A = μ k w A = (0,3)(80) = 24 N
Lus teb:
Kev ua kom lub kaw lus nrawm dua:
Σ F = ma
w B – fk = (m A + m B ) a
120 – 24 = ( 8 + 12 ) ib
96 = ( 20 ) ib
ib = 96 / 20
a = 4,8 m/s 2
Kev nruj ntawm txoj hlua:
Xav txog ib qho ntawm cov khoom, piv txwv li B.
Σ F = ma
w B – T = (mB ) a
120 – T = ( 12 ) 4,8
120 – T = 57,6
T = 120 – 57,6
T = 62,4 Newtons
Tom qab ntawd, lub thaiv C uas muaj qhov hnyav 4 kg raug muab tso rau saum lub thaiv A.
Kev ua kom lub kaw lus nrawm dua:
Σ F = ma
w B – fk = (m A + m B + m C ) a
120 – 24 = ( 8 + 12 + 4 ) ib
96 = ( 24 ) ib
ib = 96 / 24
a = 4 m/s 2
Kev nruj ntawm txoj hlua:
Xav txog ib qho ntawm cov khoom, piv txwv li B.
Σ F = ma
w B – T = (mB ) a
120 – T = ( 12 ) 4
120 – T = 48
T = 120 – 48
T = 72 Newtons
Cov lus teb yog lawm yog A.
12. Los ntawm daim duab hauv qab no, thaiv A muaj qhov hnyav ntawm 2 kg thiab thaiv B = 1 kg. Thaiv B pib nres thiab tom qab ntawd txav mus rau hauv qab kom txog thaum nws kov hauv pem teb. Yog tias g = 10 ms -2 , tus nqi ntawm qhov nro hauv txoj hlua T yog...
A. 20,0 Newtons
B. 10,0 Newton
C. 6,7 Newton
D. 3,3 Newton
E. 1,7 Newtons
Kev Sib Tham
Nws yog paub :
Qhov hnyav ntawm thaiv A (mA) = 2 kg
Qhov hnyav ntawm thaiv B (mB) = 1 kg
Kev nrawm vim lub ntiajteb txawj nqus (g) = 10 m/s2
Qhov hnyav ntawm thaiv B (w)B) = mB g = (1)(10) = 10 Newtons
Nug Tus nqi ntawm txoj hlua khi (T)
Jawb :
Hauv lo lus nug tsis muaj cov ntaub ntawv hais txog kev sib txhuam, yog li tsuas yog tsis quav ntsej txog kev sib txhuam.
Kev ua kom lub kaw lus nrawm dua (a)
Thawj suav kev ua kom nrawm system siv cov qauv Txoj cai thib ob ntawm Newton. Lub thaiv B raug dai kom muaj lub zog ntawm lub zog nqus ntawm lub thaiv B uas txav lub thaiv B mus rau hauv qab. Lub thaiv B thiab lub thaiv A raug txuas los ntawm txoj hlua kom lub thaiv B rub lub thaiv A kom txog thaum ob qho tib si txav ua ke. Qhov txawv yog tias lub thaiv B txav mus rau hauv qab thiab lub thaiv A txav mus rau sab xis. Tsuas muaj ib lub zog sib luag rau kev txav ntawm ob lub thaiv, uas yog lub zog ntawm lub zog nqus ntawm lub thaiv B (wB). Lub ntiajteb txawj nqus thaiv A yog perpendicular rau qhov kev txav ntawm thaiv A yog li nws tsis raug coj los xav txog thaum daws qhov teeb meem. Lub zog nruj hauv txoj hlua muaj tib qhov loj raws li qhov ntev ntawm txoj hlua thiab hauv kev taw qhia sib txawv yog li lawv tshem tawm ib leeg.
∑F = ma
wB = (mA +mB) thiab
10 = (2 + 1) ib
10 = 3 ib
ib = 10/3
Kev nruj ntawm hlua (T)
Qhov kev nruj ntawm txoj hlua yog xam los ntawm kev xav txog txhua lub thaiv sib cais.
Qhov nro ntawm txoj hlua ntawm thaiv A
∑F = ma
T = mA a = (2)(10/3) = 20/3 = 6,7 Newtons
Lub zog ntawm txoj hlua khi ntawm lub thaiv B
∑F = ma
wB – T = mB a
10 – T = (1)(10/3)
10 – T = 3,3
T = 10 – 3,3 = 6,7 Newtons
Lub zog nruj ntawm txoj hlua (T) = 6,7 Newton
Cov lus teb yog C.
13. Los ntawm daim duab hauv qab no, lub thaiv A muaj qhov hnyav ntawm 2 kg thiab lub thaiv B = 1 kg. Thaum lub zog sib txhuam ntawm cov khoom A thiab lub dav hlau 2,5 Newton, thaum lub zog sib txhuam ntawm txoj hlua thiab lub pulley tsis quav ntsej, ces qhov kev nrawm ntawm ob yam khoom yog ...
A. 20,0 ms-2
B. 10,0 ms-2
C. 6,7 ms-2
D. 3,3 ms-2
E. 2,5 ms-2
Kev Sib Tham
Nws yog paub :
Qhov hnyav ntawm thaiv A (mA) = 2 kg
Qhov hnyav ntawm thaiv B (mB) = 1 kg
Lub zog sib txhuam ntawm thaiv A thiab qhov chaw tiaj tiaj (fges A) = 2,5 Newtons
Kev nrawm vim lub ntiajteb txawj nqus (g) = 10 m/s2
Qhov hnyav ntawm thaiv B (w)B) = mB g = (1)(10) = 10 Newtons
Nug : Kev nrawm ntawm ob yam khoom (a)
Jawb :
Qhov kev nrawm ntawm ob yam khoom yog xam los ntawm kev siv Newton txoj cai thib ob.
∑F = ma
wB - fges = (mA +mB) thiab
10 – 2,5 = (2 + 1) ib
7,5 = 3 ib
a = 7,5 / 3 = 2,5 m/s2
Cov lus teb yog yog E.
14. 
Saib daim duab! Thaiv A uas muaj qhov hnyav 30 kg so rau hauv pem teb du thiab txuas nrog thaiv B uas muaj qhov hnyav 10 kg los ntawm lub pulley. Thaiv B raug tuav ua ntej thiab tom qab ntawd tso tawm kom nws txav mus rau hauv qab. Qhov kev nrawm ntawm lub kaw lus yog… (g = 10 m/s)-2)
A. 2,5 ms-2
B. 10 ms-2
C. 12 ms-2
D. 15 ms-2
E. 18 ms-2
Kev Sib Tham
Nws yog paub :
Qhov hnyav ntawm thaiv A (mA) = 30 kg
Qhov hnyav ntawm thaiv B (mB) = 10 kg
Kev nrawm vim lub ntiajteb txawj nqus (g) = 10 m/s2
Qhov hnyav ntawm thaiv B (w)B) = mB g = (10)(10) = 100 Newtons
Nug : Kev ua kom lub kaw lus nrawm dua (a)
Jawb :
∑F = ma
wB = (mA +mB) thiab
100 = (30 + 10) ib
100 = 40 ib
ib = 100 / 40
ib = 2,5 m/s2
Cov lus teb yog lawm yog A.
Qhov chaw nug lus:
Cov Lus Nug Txog Kev Xeem Physics Hauv Tebchaws Rau Tsev Kawm Ntawv Theem Siab/Tsev Kawm Ntawv Theem Siab Ua Haujlwm
