3 Cov Lus Nug Txog Kev Sib Npaug Ntawm Txoj Hlua
1. Daim duab hauv qab no qhia peb lub blocks, uas yog A, B thiab C uas nyob rau ntawm ib lub dav hlau kab rov tav. Yog tias qhov hnyav A = 1 kg, qhov hnyav B = 2 kg thiab qhov hnyav C = 2 kg thiab F = 10 N, ces txiav txim siab qhov piv ntawm qhov kev nruj hauv txoj hlua ntawm A thiab B rau qhov kev nruj hauv txoj hlua ntawm B thiab C.
Paub:
Qhov hnyav ntawm A (mA) = 1 kg
Qhov hnyav B (mB) = 2 kg
Qhov hnyav ntawm C (mC) = 2 kg
Lub zog tensile (F) = 10 N
SE pob: TAB : TwmBC
tshuaj:
Xam qhov kev nrawm ntawm lub system siv Newton's Second Law formula:
ΣF = ma
F = (mA +mB +mC) thiab
10 = (1 + 2 + 2) ib
10 = 5 ib
ib = 10 / 5
ib = 2 m/s2
Siv cov qauv ntawm txoj hlua khi los xam TAB
ΣF = ma
TAB = kuvA a = 1 (2) = 2 Newtons
Siv cov qauv ntawm txoj hlua khi los xam TBC
ΣF = ma
TBC = (mA +mB) a = (1 + 2) (2) = (3)(2) = 6 Newtons
2. Khoom A uas hnyav 6 kg thiab khoom B uas hnyav 3 kg raug txuas los ntawm ib txoj hlua raws li qhia. Yog tias tus coefficient ntawm kev sib txhuam yog 0.3 thiab g = 10 m/s2, txiav txim siab qhov kev nrawm ntawm cov khoom thiab qhov kev nruj ntawm cov hlua ntawm txhua lub thaiv.
Paub Tias:
Qhov hnyav ntawm yam khoom A (mA) = 6 kg
Qhov hnyav ntawm yam khoom B (mB) = 3 kg
Kev sib txhuam ntawm lub thaiv A (µ)k= 0.3 TZS
Kev nrawm vim lub ntiajteb txawj nqus (g) = 10 m/s2
Qhov hnyav ntawm thaiv A (w)A) = mA g = (6)(10) = 60 N
Lub zog ib txwm muaj rau ntawm thaiv A (N)A) = wA = 60 N
Qhov hnyav ntawm thaiv B (w)B) = mB g = (3)(10) = 30 N
SE pob: Qhov kev nrawm ntawm lub kaw lus (a) thiab qhov nro hauv txoj hlua (T)
tshuaj:
Xam lub zog kinetic frictional force piv txwv li lub zog frictional thaum thaiv A txav mus los:
Fk = µk NA = (0,3)(60) = 18 Newtons
Xam qhov kev nrawm ntawm lub kaw lus (a):
ΣF = ma
wB – Fk = (mA +mB) thiab
30 – 18 = (6 + 3) ib
12 = 9 ib
a = 12 / 9 = 1,3 m/s2
Xam qhov nro ntawm txoj hlua ntawm thaiv A (T)A):
ΣF = ma
TA - Fk = (mA) thiab
TA – 18 = (6)(1,3)
TA - 18 = 7,8
TA = 7,8 + 18 = 25,8 Newtons
Xam qhov nro ntawm txoj hlua ntawm lub beam B (T)B):
ΣF = ma
wB - TB = kuvB (A)
30 – TB = 3 (1,3)
30 – TB = 3,9
TB = 30-3,9
TB = 26,1 Newtons
3. Ob yam khoom A thiab B uas muaj qhov hnyav ntawm 5 kg thiab 3 kg raug txuas los ntawm lub pulley uas tsis muaj kev sib txhuam. Lub zog P raug siv rau lub pulley mus rau sab saud. Yog tias ob lub blocks pib so ntawm hauv pem teb, qhov kev nrawm ntawm lub block A yog dab tsi, yog tias qhov loj ntawm P yog 60 N?
Txheeb xyuas qhov nro ntawm txoj hlua ntawm cov blocks A thiab B.
Paub Tias:
Kev nrawm vim lub ntiajteb txawj nqus (g) = 10 m/s2
Qhov hnyav ntawm A (mA) = 5 kg
Qhov hnyav ntawm thaiv A (w)A) = mA g = (5)(10) = 50 Newtons
Qhov hnyav B (mB) = 3 kg
Qhov hnyav ntawm thaiv B (w)B) = mB g = (3)(10) = 30 Newtons
Lub zog P = 60 N
SE pob: Kev ua kom nrawm ntawm lub kaw lus ntawm cov nqaj A thiab B (a) thiab qhov nro hauv txoj hlua ntawm cov nqaj A (TA) thiab lub teeb B (TB)
tshuaj:
Xam qhov kev nrawm ntawm lub system siv Newton's Second Law formula.
ΣF = ma
wA - wB = (mA +mB) thiab
50 – 30 = (5 + 3) ib
20 = 8 ib
ib = 20 / 8
ib = 2,5 m/s2
Siv cov qauv tension force los xam qhov tension hauv txoj hlua
Lub zog ntawm txoj hlua ntawm thaiv A:
ΣF = ma
wA - TA = kuvA a
50 – TA = 5 (2,5)
50 – TA = 12,5
TA = 50 – 12,5 = 37,5 Newtons
Lub zog ntawm txoj hlua khi ntawm thaiv B:
ΣF = ma
TB - wB = kuvB a
TB – 30 = 3 (2,5)
TB - 30 = 7,5
TB = 7,5 + 30 = 37,5 Newtons
