Mafunso atatu okhudza Friction force equation
1. Block A 3 kg imayikidwa patebulo kenako imamangidwa ku chingwe chomwe chimalumikizidwa ndi miyala B = 2 kg kudzera mu pulley monga momwe zasonyezedwera. Kulemera ndi kukangana kwa ma pulleys kumanyalanyazidwa. Kuthamanga chifukwa cha mphamvu yokoka g = 10 m/s 2 . Dziwani kuthamanga kwa dongosolo ndi kupsinjika kwa chingwe ngati:
a) tebulo losalala
b) tebulo lozungulira lokhala ndi coefficient ya kinetic friction ya 0.4
Zodziwika:
Kulemera kwa chipika A (m A ) = 3 kg
Kulemera kwa thanthwe B (m B ) = 2 kg
Kuthamanga chifukwa cha mphamvu yokoka (g) = 10 m/s 2
Kulemera kwa chipika A (w A ) = mg = (3)(10) = 30 Newtons
Kulemera kwa thanthwe B (w B ) = mg = (2)(10) = 20 Newtons
Kufunidwa: Kuthamanga kwa dongosolo (a) ndi kukakamira kwa chingwe (T)
yankho;
a) tebulo losalala
Werengerani kuthamanga kwa dongosololi pogwiritsa ntchito njira ya lamulo lachiwiri la Newton:
ΣF = ma
w B = (m A + m B ) a
20 = (3 + 2) a
20 = 5 a
a = 20 / 5 = 4 m/s 2
Werengerani mphamvu ya chingwe pogwiritsa ntchito njira ya mphamvu ya chingwe:
Kupsinjika kwa chingwe pa block A:
ΣF = m A a
T = m A a = (3)(4) = 12 Newtons
Kukakamira kwa chingwe pa bolodi B:
ΣF = m B a
w B – T = (2)(4)
20 – T = 8
T = 20 – 8 = 12 Newtons
b) tebulo lozungulira lokhala ndi coefficient ya kinetic friction ya 0.4
Mphamvu ya kukangana kwa kinetic:
F k = µ k N = (0,4)(30) = 12 Newtons
Werengerani kuthamanga kwa dongosololi pogwiritsa ntchito njira ya lamulo lachiwiri la 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
Werengerani mphamvu ya chingwe pogwiritsa ntchito njira ya mphamvu ya chingwe:
Kupsinjika kwa chingwe pa block 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
Kukakamira kwa chingwe pa bolodi B:
ΣF = m B a
w B – T = (2)(1,6)
20 – T = 3,2
T = 20 – 3,2 = 16,8 Newtons
2. Chinthu cholemera makilogalamu 10 chimakhala chopingasa. Coefficient of static friction ndi 0.4 ndipo coefficient of kinetic friction ndi 0.35. g = 10 m/s 2. Ngati chinthu chapatsidwa mphamvu yokhazikika yopingasa ya 25 N, kukula kwa mphamvu yokangana yomwe ikugwira ntchito pa chinthucho ndi…
Zodziwika:
Kulemera kwa chinthucho (m) = 10 kg
Chiŵerengero cha kupsinjika kosasunthika (µs ) = 0.4
Chiŵerengero cha kupsinjika kwa kinetic (µk) = 0.35
Kuthamanga chifukwa cha mphamvu yokoka (g) = 10 m/s 2
Mphamvu yopingasa (F) = 25 N
Mphamvu yokoka ya chinthu (w) = mg = (10)(10) = 100 Newtons
Mphamvu yachibadwa (N) = w = 100 Newtons
Kufunidwa: Kuchuluka kwa kukangana kosasinthasintha (f s ) ndi kinetic (f k )
yankho;
Mphamvu ya kukangana kosasinthasintha::
f s = µ s N = (0,4) (100) = 40 Newtons
Mphamvu ya Kinetic Friction:
f k = µ k N = (0,35)(100) = 35 Newtons
Mphamvu yopingasa ndi ma Newton 25 okha kotero singathe kusuntha zinthu pakadali pano.
3. Unyinji wa mabuloko A ndi B pachithunzichi ndi 10 kg ndi 5 kg motsatana. Kuchuluka kwa kukangana pakati pa boloko A ndi ndege ndi 0.2. Kuti block A isasunthe, unyinji wocheperako wa boloko C wofunikira ndi…
Zodziwika:
Kulemera kwa chipika A (m A ) = 10 kg
Kulemera kwa chipika B (m B ) = 5 kg
Koyefifiti ya kukangana kosasinthasintha kwa block A (µs ) = 0,2
Kuthamanga kwa mphamvu yokoka (g) = 10 m/s 2
Kulemera kwa chipika A (w A ) = m A g = (10)(10) = 100 Newtons
Kulemera kwa chipika B (w B ) = m B g = (5)(10) = 50 Newtons
Kukangana kosasinthasintha (fs ) = µs N = (0,2)(w A + w C ) = (0,2)(100 + w C ) = 20 + 0,2 w C
Kufunsa: Kulemera kwa chipika C kuti dongosolo likhale lokhazikika
Yankho:
Dongosololi lili pamtendere kotero njira ya lamulo loyamba la Newton imagwiritsidwa ntchito:
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
Kulemera kwa chipika C = 150 / 10 = 15 Kg
