3 mau nīnau e pili ana i ka hoʻohālikelike ikaika friction
1. Ua kau ʻia ka poloka A 3 kg ma luna o ka papa ʻaina a laila nakinaki ʻia i ke kaula i hoʻopili ʻia i ka pōhaku B = 2 kg ma o kahi pulley e like me ka mea i hōʻike ʻia. Ua hoʻowahāwahā ʻia ka nuipa a me ka friction o nā pulley. Ka wikiwiki ma muli o ke umekaumaha g = 10 m/s 2. E hoʻoholo i ka wikiwiki o ka ʻōnaehana a me ke kaumaha i loko o ke kaula inā:
a) papa laumania
b) papa ʻaina ʻino me kahi coefficient o ka friction kinetic o 0.4
ʻIke ʻia:
ʻO ke kaumaha o ka poloka A (m A ) = 3 kg
ʻO ke kaumaha o ka pōhaku B (m B ) = 2 kg
Ka wikiwiki ma muli o ke koʻikoʻi (g) = 10 m/s 2
Kaumaha o ka poloka A (w A ) = mg = (3)(10) = 30 Newtons
Kaumaha o ka pōhaku B (w B ) = mg = (2)(10) = 20 Newtons
Makemake ʻia: ʻO ka wikiwiki o ka ʻōnaehana (a) a me ke kaumaha ma ke kaula (T)
pāʻoihana:
a) papa laumania
E helu i ka wikiwiki o ka ʻōnaehana me ka hoʻohana ʻana i ke ʻano no ke kānāwai ʻelua o Newton:
ΣF = ma
w B = (m A + m B ) a
20 = (3 + 2) a
20 = 5 a
a = 20 / 5 = 4 m/s 2
E helu i ke kaumaha ma ke kaula me ka hoʻohana ʻana i ke ʻano no ke kaumaha ma ke kaula:
ʻO ke kaumaha o ke kaula ma ka poloka A:
ΣF = m A a
T = m A a = (3)(4) = 12 Newtons
ʻO ke kaumaha o ke kaula ma ka poloka B:
ΣF = m B a
w B – T = (2)(4)
20 – T = 8
T = 20 – 8 = 12 Newton
b) papa ʻaina ʻino me kahi coefficient o ka friction kinetic o 0.4
Ka ikaika o ka haʻalulu kinetic:
F k = µ k N = (0,4)(30) = 12 Newtons
E helu i ka wikiwiki o ka ʻōnaehana me ka hoʻohana ʻana i ke ʻano no ke kānāwai ʻelua o Newton:
ΣF = ma
w B – f k = (m A + m B ) a
20 – 12 = (3 + 2) a
8 = 5 a
a = 8 / 5 = 1,6 m/s 2
E helu i ke kaumaha ma ke kaula me ka hoʻohana ʻana i ke ʻano no ke kaumaha ma ke kaula:
ʻO ke kaumaha o ke kaula ma ka poloka A:
ΣF = m A a
T – fk = m A a
T – 12 = (3)(1,6)
T – 12 = 4,8
T = 4,8 + 12 = 16,8 Newtons
ʻO ke kaumaha o ke kaula ma ka poloka B:
ΣF = m B a
w B – T = (2)(1,6)
20 – T = 3,2
T = 20 – 3,2 = 16,8 Newton
2. Aia kahi mea me ke kaumaha o 10 kg i loko o kahi mokulele ākea. ʻO ke koina o ka friction static he 0.4 a ʻo ke koina o ka friction kinetic he 0.35. g = 10 m/s 2. Inā hāʻawi ʻia kahi mea i kahi ikaika ākea mau o 25 N, ʻo ka nui o ka ikaika friction e hana ana ma luna o ka mea…
ʻIke ʻia:
ʻO ke kaumaha o ka mea (m) = 10 kg
ʻO ke koina o ka haʻalulu paʻa (µs ) = 0.4
ʻO ke koina o ka friction kinetic (µk) = 0.35
Ka wikiwiki ma muli o ke koʻikoʻi (g) = 10 m/s 2
Ka ikaika pae (F) = 25 N
ʻO ke kaumaha o ka mea (w) = mg = (10)(10) = 100 Newtons
Ka ikaika maʻamau (N) = w = 100 Newtons
Makemake ʻia: ʻO ka nui o ka friction static (fs ) a me ke kinetic ( fk )
pāʻoihana:
Ka ikaika o ka haʻalulu paʻa::
f s = µ s N = (0,4)(100) = 40 Newtons
Ka ikaika o ka friction kinetic:
f k = µ k N = (0,35)(100) = 35 Newtons
He 25 Newtons wale nō ka ikaika ākea no laila ʻaʻole hiki iā ia ke hoʻoneʻe i nā mea i kēia manawa.
3. ʻO nā kaumaha o nā poloka A a me B ma ke kiʻi he 10 kg a me 5 kg. ʻO ke koina o ka friction ma waena o ka poloka A a me ka mokulele he 0.2. I mea e pale ai i ka neʻe ʻana o ka poloka A, ʻo ka nui haʻahaʻa loa o ka poloka C i koi ʻia…
ʻIke ʻia:
ʻO ke kaumaha o ka poloka A (m A ) = 10 kg
ʻO ke kaumaha o ka poloka B (m B ) = 5 kg
ʻO ke koina o ka haʻalulu paʻa o ka poloka A (µs ) = 0,2
Ka wikiwiki o ke kaumaha (g) = 10 m/s 2
Kaumaha poloka A (w A ) = m A g = (10)(10) = 100 Newtons
Kaumaha poloka B (w B ) = m B g = (5)(10) = 50 Newtons
Ka ʻūmiʻi paʻa (fs ) = µsN = (0,2)(wA + wC ) = (0,2)(100 + wC ) = 20 + 0,2 wC
Nīnau ʻia: ʻO ke kaumaha o ka poloka C e hoʻomaha ai i ka ʻōnaehana
Pane:
Ua hoʻomaha ka ʻōnaehana no laila ua hoʻohana ʻia ke ʻano no ke kānāwai mua o Newton:
ΣF = 0
w B – f s = 0
50 – (20 + 0,2 w C ) = 0
50 – 20 – 0,2 w C = 0
30 – 0,2 w C = 0
30 = 0,2 w C
w C = 30 / 0,2 = 300 / 2 = 150 Newtons
ʻO ke kaumaha o ka poloka C = 150 / 10 = 15 Kg
