1. Tanthauzo la mphamvu yokangana
Kukangana ndi kukoka komwe kumagwira ntchito pakati pa zinthu zomwe zimagwirizana. Munkhaniyi, mphamvu yokangana yomwe yaphunziridwa ikugwirizana ndi mphamvu yokangana yomwe imagwira ntchito pakati pa malo awiri olimba a thupi omwe amakhudza. Monga kukangana pakati pa maziko a mtengo ndi pansi, kukangana pakati pa maziko a nsapato ndi pansi, kukangana pakati pa mawilo a galimoto ndi pamwamba pa msewu.
Mphamvu yokangana nthawi zonse imagwira ntchito pamwamba pa zinthu zolimba zomwe zimakhudzana, ngakhale zinthuzo zili zosalala kwambiri. Ngakhale malo osalala kwenikweni amakhala okhwima kwambiri pa sikelo ya microscopic. Chinthu chikasuntha, mitsinje iyi ya microscopic imasokoneza kayendedwe kake. Pa mulingo wa atomiki, kutuluka pamwamba kumapangitsa maatomu kukhala pafupi kwambiri ndi malo ena, kotero kuti mphamvu zamagetsi pakati pa maatomu zimatha kupanga ma bond a mankhwala, monga mgwirizano pakati pa malo awiri a chinthu choyenda. Chinthu chikasuntha, mwachitsanzo mukakankhira buku pamwamba pa tebulo, kuyenda kwa buku kumakumana ndi zopinga ndipo pamapeto pake kumayima. Izi zimachitika chifukwa cha kupangika ndi kumasulidwa kwa bond.
Ngati pamwamba pa chinthu chikugundana pamwamba pa chinthu china, chilichonse mwa zinthuzi chimagwira ntchito pa kukangana pakati pa china ndi china. Mphamvu yokangana pa chinthu choyenda nthawi zonse imakhala yosiyana ndi momwe chinthucho chimayendera. Kuwonjezera pa kuletsa kuyenda kwa zinthu, kukangana kungayambitse kuwonongeka ndi kuwonongeka. Titha kuwona izi pa injini ya galimoto. Mwachitsanzo, tikamapereka mafuta odzola ku injini ya njinga yamoto, timafunadi kuchepetsa mphamvu yokangana yomwe imachitika mkati mwa injini. Ngati mafuta odzola sanapatsidwe, injini ya galimoto yathu imawonongeka mwachangu. Chitsanzo ichi ndi chimodzi mwa zinthu zomwe zimatayika chifukwa cha kukangana.
2. Mitundu ya mphamvu zokangana
Pali mitundu iwiri ya mphamvu zokangana, zomwe ndi mphamvu ya kukangana kosasinthasintha (fs ) ndi mphamvu ya kukangana kosasinthasintha (f k ). Mphamvu yokangana yosasinthasintha imagwira ntchito pamene chinthucho sichinasunthe, pomwe mphamvu yokangana yosasinthasintha imagwira ntchito pamene chinthucho chikuyenda. Ngati mutakankhira tebulo, koma tebulo silinasunthe, ndiye kuti mphamvu yokangana yomwe ikugwira ntchito patebulo lomwe lili pamalo ake ndi mphamvu yokangana yosasinthasintha. Mosiyana ndi zimenezi, pamene tebulo likuyenda, mphamvu yokangana yomwe ikugwira ntchito patebulo ndi kukangana kosasinthasintha. Ngati tebulo loyenda silikukankhidwa nthawi zonse, tebulo lidzaima pambuyo poyenda kwa kanthawi. Tebulo limaima chifukwa cha mphamvu yokangana yosasinthasintha yomwe imaletsa kuyenda kwa tebulo.
Kodi munayamba mwatsetsereka mukaponda chinthu chosalala? Mukatsetsereka, mphamvu yokangana yomwe imagwira ntchito pakati pa maziko a nsapato kapena pansi pa sandali yokhala ndi malo osalala ndi kukangana kwa kinetic. Vutoli limafanana ndi pamene njinga yamoto kapena galimoto ikuyenda pamwamba pa msewu wonyowa komanso wosalala, ndikuyimitsa mpaka gudumu litatsika. Mawilo akatsetsereka, mphamvu yokangana yomwe imagwira ntchito pamwamba pa gudumu ndi pamwamba pa msewu ndi mphamvu yokangana ya kinetic. Mosiyana ndi zimenezi, mukayenda, mphamvu yokangana yomwe imagwira ntchito pakati pa maziko a nsapato kapena pansi pa sandali yokhala ndi malo otsetsereka ndi mphamvu yokangana yosasinthasintha. Mofananamo, pamene mawilo satsetsereka, mphamvu yokangana yomwe imagwira ntchito pamwamba pa gudumu ndi msewu ndi kukangana kosasinthasintha.
2.1 Mphamvu yosasunthika yokangana
Mphamvu yokangana yosasinthasintha ndi mphamvu yokangana yomwe imagwira ntchito pamwamba pa zinthu zomwe zimakhudzana pamene zinthu sizinayendebe.
Chithunzi 1 chikuwonetsa chinthu chomwe chili pamwamba pa malo osalala. Ngati chinthucho sichinasunthebe, ndiye kuti mphamvu yokangana yosasunthika (fs) ndi yaying'ono kuposa mphamvu yokoka (F). Ngati ikupitiriza kukokedwa, ndiye kuti chinthucho chidzasuntha. Chinthu choyenera chikasuntha, kukula kwa mphamvu yokangana yosasunthika (f)s) ndi kukula kwa mphamvu yokoka (F).
Lamulo Loyamba la Newton limati zinthu ndi mpumulo ngati mphamvu yonse (mphamvu yotuluka) ili zero.
ΣF y = 0 (Pezani chinthucho ndipo musasunthe molunjika)
N – w = 0
N = w (1.2)
Sinthani N mu equation 1.1 ndi N mu equation 1.2
f s = μ s w
f s = μ s mg (1.3)
fs = kukangana kosasinthasintha (N), μs = coefficient ya kukangana kosasinthasintha, N = mphamvu yachibadwa (N), w = mphamvu yokoka (N), m = kulemera (kg), g = kufulumira kwa mphamvu yokoka (m/s 2 )
Ngati mukufuna kudziwa coefficient ya static friction, gwiritsani ntchito equation 1.1 b
Σf x = 0 (Chinthu chimapumula ndipo sichisuntha mopingasa)
F – f s = 0
F = fs ( 1.4)
Chinthucho chikayamba kuyenda, mphamvu yayikulu yokankhira yosasunthika imafanana ndi mphamvu yokankhira kapena kukoka.
2.2 Mphamvu ya kukangana kwa kinetic
Mphamvu yolimbana ndi zinthu (kinetic friction force) ndi mphamvu yolimbana yomwe imagwira ntchito pamwamba pa zinthu zomwe zimakhudzana pamene chinthu chikuyenda.
Ngati mukufuna kudziwa coefficient ya kinetic friction (μ k ), gwiritsani ntchito equation 1.5 b
Chithunzi 2 chikuwonetsa chinthu chomwe chikukokedwa nthawi zonse kuti chinthucho chiziyenda pa liwiro losasintha. Poyenda pa liwiro losasintha, kukula kwa mphamvu ya kinetic friction (fk) kumafanana ndi kukula kwa mphamvu yokoka (F).
Lamulo Loyamba la Newton limati chinthu chimayenda pa liwiro losasintha ngati mphamvu yonse (mphamvu yotuluka) ili zero.
ΣF x = 0 (zinthu zimayenda pa liwiro losasintha mbali yopingasa)
F – f k = 0
F = f k (1.6)
Chitsanzo cha vuto 1:
Wophunzira akukoka mtanda wolemera makilogalamu 1 womwe uli pamwamba pa tebulo pogwiritsa ntchito dynamometer (chipangizo choyezera mphamvu). Mtanda ukasuntha, dynamometer imasonyeza nambala 2 N. Ngati kuthamanga kwa mphamvu yokoka = 10 m/s 2 , dziwani (a) kukula kwa mphamvu yokangana yokhazikika (b) coefficient ya static friction
yankho;
Yodziwika : m = 1 kg, F = 2 N, g = 10 m/s 2 , w = mg = 10 N
(a) fs
Pamene mtandawo usuntha, kukula kwa mphamvu yosasunthika yokangana = kukula kwa mphamvu yokoka (yerekezerani equation 1.4). Chifukwa chake, f s = F = 2 N.
(b) μ s
f s = μ s w
2 N = (μ s )(10 N)
μ s = 2 N / 10 N = 0.2
Chitsanzo cha vuto 2:
Mtanda wokhala ndi kulemera kwa 1 kg womwe uli pamwamba pa tebulo umakokedwa nthawi zonse kuti mtandawo usunthe pa liwiro losasintha. Mtandawo ukasuntha pa liwiro losasintha, dynamometer imasonyeza nambala 1 N. Ngati kuthamanga kwa mphamvu yokoka = 10 m/s 2 , dziwani (a) kukula kwa mphamvu ya kugwedezeka kwa kinetic (b) coefficient ya kugwedezeka kwa kinetic
yankho;
Zodziwika: m = 1 kg, g = 10 m/s 2 , F = 1 N, w = mg = 10 N
(a) f k
Pamene mtandawo ukuyenda nthawi zonse kapena ukuyenda pa liwiro losasintha, kukula kwa mphamvu ya kinetic friction force = kukula kwa mphamvu yokoka (yerekezerani ndi equation 1.6).
Kotero f k = F = 1 N
(b) μ k
f k = μ k w
1 N = (μ k )(10 N)
μ k = 1 N / 10 N = 0.1
