1. Ma'anar ƙarfin gogayya
Fogewa wata hanya ce ta jan hankali da ke aiki tsakanin saman abubuwan da ke taɓa juna. A cikin wannan batu, ƙarfin gogayya da aka yi nazari a kai yana da alaƙa da ƙarfin gogayya da ke aiki tsakanin saman jiki guda biyu masu ƙarfi waɗanda ke taɓawa. Kamar gogayya tsakanin tushen katako da saman bene, gogayya tsakanin tushen takalma da saman bene, gogayya tsakanin ƙafafun motar da saman hanya.
Ƙarfin gogayya koyaushe yana aiki akan saman abubuwa masu ƙarfi waɗanda ke taɓa juna, duk da cewa abubuwan suna da santsi sosai. Har ma saman masu santsi a zahiri suna da ƙarfi sosai akan sikelin ƙananan ƙwayoyin cuta. Lokacin da abu ya motsa, waɗannan ƙananan duwawu suna tsoma baki tare da motsi. A matakin atom, fitowar da ke kan saman yana sa atoms su kasance kusa da sauran saman, don haka ƙarfin lantarki tsakanin atoms na iya samar da haɗin sinadarai, a matsayin haɗin kai tsakanin saman abu biyu na abin da ke motsi. Lokacin da abu ya motsa, misali lokacin da ka tura littafi a saman tebur, motsin littafin yana fuskantar cikas kuma a ƙarshe ya tsaya. Wannan ya faru ne saboda samuwar da sakin haɗin.
Idan saman wani abu ya shafa a saman wani abu, kowanne daga cikin waɗannan abubuwa yana aiki ne akan gogayya tsakanin juna. Ƙarfin gogayya akan abin da ke motsi koyaushe yana akasin alkiblar motsi na abin. Baya ga hana motsi na abubuwa, gogayya na iya haifar da lalacewa da lalacewa. Za mu iya lura da wannan a kan injin abin hawa. Misali, lokacin da muka samar da mai mai shafawa ga injin babur, a zahiri muna son rage ƙarfin gogayya da ke faruwa a cikin injin. Idan ba a ba shi mai mai shafawa ba, injin motarmu yana lalacewa da sauri. Wannan misali yana ɗaya daga cikin asarar da gogayya ke haifarwa.
2. Iri na ƙarfin gogayya
Akwai nau'ikan ƙarfin gogayya guda biyu, wato ƙarfin gogayya mai tsayi (f s ) da ƙarfin gogayya mai tsayi (f k ). Ƙarfin gogayya mai tsayi yana aiki lokacin da abin bai motsa ba, yayin da ƙarfin gogayya mai tsayi yana aiki lokacin da abin yake motsi. Idan ka tura tebur, amma teburin bai motsa ba, to ƙarfin gogayya da ke aiki akan teburin da ke hutawa ƙarfin gogayya ne. Akasin haka, lokacin da teburin ke motsi, ƙarfin gogayya da ke aiki akan teburin gogayya ne. Idan teburin da ke motsi ba koyaushe ake tura shi ba, teburin zai tsaya bayan ya motsa na ɗan lokaci. Teburin yana tsayawa saboda ƙarfin gogayya mai tsayi wanda ke toshe motsin teburin.
Shin ka taɓa zamewa lokacin da ka taka wani abu mai santsi? Idan ka zame, ƙarfin gogayya da ke aiki tsakanin tushen takalmin ko ƙasan sandal mai santsi shine gogayya ta motsi. Wannan matsalar tana kama da lokacin da babur ko mota ke motsawa akan saman hanya mai danshi da santsi, tana birki har sai ƙafafun sun zame. Lokacin da ƙafafun suka zame, ƙarfin gogayya da ke aiki akan saman ƙafafun da saman hanya shine ƙarfin gogayya ta motsi. Akasin haka, lokacin da kake tafiya, ƙarfin gogayya da ke aiki tsakanin tushen takalma ko ƙasan takalman tare da saman bene shine ƙarfin gogayya mai motsi. Haka kuma, lokacin da ƙafafun ba su zame ba, ƙarfin gogayya da ke aiki akan saman ƙafafun da hanya shine gogayya mai motsi.
2.1 Ƙarfin gogayya mara motsi
Ƙarfin gogayya mai motsi shine ƙarfin gogayya da ke aiki a saman abubuwan da ke taɓa juna lokacin da abubuwa ba su motsa ba tukuna.
Hoto na 1 ya nuna wani abu da har yanzu yana kan saman jirgin sama mai faɗi. Idan abin bai motsa ba tukuna, to ƙarfin gogayya mai tsauri (fs) ya fi ƙarfin ja (F) ƙanƙanta. Idan aka ci gaba da ja, to abin zai motsa. Lokacin da abin da ya dace zai motsa, girman ƙarfin gogayya mai tsauri (f)s) yayi daidai da girman ƙarfin jan (F).
Dokar Farko ta Newton ta bayyana cewa abubuwa su ne hutawa idan jimlar ƙarfin (ƙarfin sakamako) sifili ne.
ΣF y = 0 (Saita abu kuma kada ya motsa a tsaye)
N – w = 0
N = w (1.2)
Maye gurbin N a cikin lissafi 1.1 da N a cikin lissafi 1.2
f s = μ s w
f s = μ s mg (1.3)
fs = gogayya mai motsi (N), μs = ma'aunin gogayya mai motsi, N = ƙarfin al'ada (N), w = nauyi (N), m = nauyi (kg), g = hanzarin nauyi (m/s 2 )
Idan kana son tantance ma'aunin gogayya mai tsauri, to yi amfani da lissafi 1.1 b
Σf x = 0 (Abu yana tsayawa kuma baya motsawa a cikin alkiblar kwance)
F – f s = 0
F = fs ( 1.4)
Lokacin da abin ya fara motsawa, matsakaicin ƙarfin gogayya mai tsauri yana daidai da girman ƙarfin turawa ko ja.
2.2 Ƙarfin gogayya na motsi
Ƙarfin gogayya mai motsi shine ƙarfin gogayya da ke aiki a saman abubuwan da ke taɓa juna lokacin da wani abu ke motsi.
Idan kana son tantance ma'aunin gogayya mai motsi (μ k ), yi amfani da lissafi 1.5 b
Siffa ta 2 ta nuna wani abu da ake jan shi akai-akai don haka abin yana motsawa a gudun da ba ya canzawa. Lokacin da ake motsi a gudun da ba ya canzawa, girman ƙarfin gogayya (fk) yana daidai da girman ƙarfin ja (F).
Dokar Farko ta Newton ta bayyana cewa abu yana motsawa a gudun da ba ya canzawa idan jimlar ƙarfin (ƙarfin da ya haifar) sifili ne.
ΣF x = 0 (abubuwa suna motsawa a gudun da ba ya canzawa a cikin alkiblar kwance)
F – f k = 0
F = f k (1.6)
Misalin matsala ta 1:
Ɗalibi yana jan katako mai nauyin kilogiram 1 wanda ke kan saman teburin ta amfani da na'urar auna ƙarfi (na'urar auna ƙarfi). Lokacin da katakon zai motsa, na'urar auna ƙarfi tana nuna lamba 2 N. Idan hanzarin nauyi = 10 m/s 2 , ƙayyade (a) girman ƙarfin gogayya mai tsayi (b) ma'aunin gogayya mai tsayi
Magani:
An san : m = 1 kg, F = 2 N, g = 10 m/s 2 , w = mg = 10 N
(a) f s
Lokacin da hasken zai motsa, girman ƙarfin gogayya mai motsi = girman ƙarfin ja (kwatanta lissafi 1.4). Don haka, f s = F = 2 N.
(b) μ s
f s = μ s w
2 N = (μs ) (10 N)
μ s = 2 N / 10 N = 0.2
Misalin matsala ta 2:
Ana jan katako mai nauyin kilogiram 1 da ke saman saman teburin akai-akai don hasken ya motsa a cikin gudu mai daidaito. Lokacin da hasken ya motsa a cikin gudu mai daidaito, injin aunawa yana nuna lamba 1 N. Idan hanzarin nauyi = 10 m/s 2 , ƙayyade (a) girman ƙarfin gogayya na motsi (b) ma'aunin gogayya na motsi
Magani:
Sananne: m = 1 kg, g = 10 m/s 2 , F = 1 N, w = mg = 10 N
(a) f k
Idan hasken ke motsawa akai-akai ko kuma yana motsawa a daidai gudun, girman ƙarfin gogayya na motsi = girman ƙarfin ja (kwatanta lissafi 1.6).
Don haka 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
