1. Tsanangudzo yesimba rekukweshana
Kukweshana kunoshanda pakati pezvinhu zvinobatana. Munyaya iyi, simba rekukweshana radzidzwa rine chekuita nesimba rekukweshana rinoshanda pakati penzvimbo mbiri dzemuviri dzakasimba dzinobatana. Zvakadai sekukweshana pakati pehwaro hwedanda nepasi, kukweshana pakati pehwaro hweshangu nepasi, kukweshana pakati pemavhiri emotokari nepamusoro pemugwagwa.
Simba rekukweshana rinoshanda nguva dzose pamusoro pezvinhu zvakasimba zvinobatana, kunyangwe zvinhu zvacho zvakatsetseka. Kunyangwe nzvimbo dzakatsetseka dzakanyatsoomarara pachiyero chidiki. Kana chinhu chichifamba, mitsetse iyi midiki inokanganisa kufamba. Padanho reatomu, kubuda pamusoro kunoita kuti maatomu ave pedyo zvikuru nedzimwe nzvimbo, zvekuti masimba emagetsi ari pakati peatomu anogona kuumba zvisungo zvemakemikari, sekubatana pakati penzvimbo mbiri dzechinhu chinofamba. Kana chinhu chichifamba, semuenzaniso paunosundira bhuku pamusoro petafura, kufamba kwebhuku kunosangana nezvipingamupinyi uye pakupedzisira kunomira. Izvi zvinokonzerwa nekuumbwa nekusunungurwa kwechisungo.
Kana pamusoro pechinhu chikakwiza pamusoro pechimwe chinhu, chimwe nechimwe chezvinhu izvi chinoshanda pakukwiza pakati pechimwe. Simba rekukwiza pachinhu chinofamba rinogara riri munzira yakatarisana nekufamba kwechinhu chacho. Pamusoro pekudzivisa kufamba kwezvinhu, kukwiza kunogona kukonzera kupfeka nekukuvadzwa. Tinogona kuona izvi painjini yemotokari. Semuenzaniso, patinopa mafuta ekuzora kuinjini yemudhudhudhu, tinoda kuderedza simba rekukwiza rinoitika mukati meinjini. Kana ikasapihwa mafuta ekuzora, injini yedu yemotokari inokuvadzwa nekukurumidza. Muenzaniso uyu ndeumwe wekurasikirwa kunokonzerwa nekukwiza.
2. Mhando dze masimba ekukakavadzana
Kune mhando mbiri dzemasimba ekukweshana, dzinoti simba rekukweshana kwakagadzika (fs ) uye simba rekukweshana kwakagadzika (f k ). Simba rekukweshana rakagadzika rinoshanda kana chinhu chisina kufamba, nepo simba rekukweshana rakagadzika richishanda kana chinhu chichifamba. Kana ukasunda tafura, asi tafura isina kufamba, simba rekukweshana rinoshanda patafura iri pakadzikama isimba rekukweshana rakagadzika. Kusiyana neizvi, kana tafura ichifamba, simba rekukweshana rinoshanda patafura isimba rekukweshana rakagadzika. Kana tafura inofamba isingagari ichisundidzirwa, tafura inomira mushure mekufamba kwenguva. Tafura inomira nekuda kwesimba rekukweshana rakagadzika rinovhara kufamba kwetafura.
Wakambotsvedza here paunenge uchitsika chimwe chinhu chakatsetseka? Paunotsvedza, simba rekukweshana rinoshanda pakati pehwaro hweshangu kana pasi peshangu rine pamusoro wakatsetseka ndiro kinetic friction. Dambudziko iri rakafanana nepaya apo mudhudhudhu kana mota inofamba pamusoro pemugwagwa wakanyorova uye wakatsetseka, ichibhureka kusvika vhiri ratsvedza. Kana mavhiri atsvedza, simba rekukweshana rinoshanda pamusoro pevhiri nepamusoro pemugwagwa ndiro kinetic friction force. Kusiyana neizvi, paunofamba, simba rekukweshana rinoshanda pakati pehwaro hweshangu kana pasi peshangu nepamusoro pepasi isimba rekukweshana rakatsetseka. Saizvozvowo, kana mavhiri asingatsvedze, simba rekukweshana rinoshanda pamusoro pevhiri nemugwagwa istatic friction.
2.1 Simba rekukweshana rakasimba
Simba rekukweshana rinomira (static friction force) isimba rekukweshana rinobata pamusoro pezvinhu zvinobata kana zvinhu zvisati zvafamba.
Mufananidzo 1 unoratidza chinhu chichiri pamusoro penzvimbo yakati sandara. Kana chinhu chisati chafamba, simba rekukweshana risingachinji (fs) diki pane simba rekukwesha (F). Kana chikaramba chichikweshana, chinhu chacho chichafamba. Kana chinhu chakarurama chichifamba, hukuru hwesimba rekukweshana risingachinji (f)s) yakaenzana nehukuru hwesimba rinodhonza (F).
Mutemo wekutanga waNewton unoti zvinhu zvinozorora kana simba rese (simba rinobuda) riri zero.
ΣF y = 0 (Zorora chinhu uye usafambe wakananga kwakamira)
N – w = 0
N = w (1.2)
Tsiva N muequation 1.1 naN muequation 1.2
fs = μs w
fs = μs mg ( 1.3)
fs = kukweshana kwakasimba (N), μs = coefficient yekukweshana kwakasimba, N = simba rakajairika (N), w = giravhiti (N), m = huremu (kg), g = kukurumidza kwegiravhiti (m/s 2 )
Kana uchida kuona coefficient ye static friction, shandisa equation 1.1 b
Σf x = 0 (Chinhu chinomira uye hachifambi munzira yakatwasuka)
F – f s = 0
F = fs ( 1.4)
Kana chinhu chacho chatanga kufamba, simba guru rekukweshana rinomira rinoenzana nehukuru hwesimba rekusunda kana rekudhonza.
2.2 Kinetic friction force
Simba rekukweshana rinoita serinokweshana (kinetic friction force) ndiro simba rekukweshana rinobata pamusoro pezvinhu zvinobata kana chinhu chichifamba.
Kana uchida kuona coefficient ye kinetic friction (μ k ), shandisa equation 1.5 b
Mufananidzo 2 unoratidza chinhu chiri kudhonzwa nguva nenguva kuitira kuti chinhu chifambe nekumhanya kwakasimba. Pakufamba nekumhanya kwakasimba, hukuru hwesimba rekukweshana kwekinetic (fk) hwakaenzana nehukuru hwesimba rekudhonza (F).
Mutemo wekutanga waNewton unoti chinhu chinofamba nekumhanya kusingachinji kana simba rese (simba rinobuda) riri zero.
ΣF x = 0 (zvinhu zvinofamba nekumhanya kusingachinji munzira yakatwasuka)
F – f k = 0
F = f k (1.6)
Dambudziko remuenzaniso 1:
Mudzidzi anodhonza danda rine huremu hwe 1 kg riri pamusoro petafura achishandisa dynamometer (mudziyo wekuyera simba). Kana danda richizofamba, dynamometer inoratidza nhamba 2 N. Kana kukurumidza kwegiravhiti = 10 m/s 2 , sarudza (a) hukuru hwesimba rekukweshana rinomira (b) chiyero chekukweshana kunomira
Solution:
Inozivikanwa : m = 1 kg, F = 2 N, g = 10 m/s 2 , w = mg = 10 N
(a) fs
Kana danda richizofamba, hukuru hwesimba rekukweshana rinomira = hukuru hwesimba rekudhonza (enzanisa equation 1.4). Saka, f s = F = 2 N.
(b) μ s
fs = μs w
2 N = (μ s )(10 N)
μ s = 2 N / 10 N = 0.2
Dambudziko remuenzaniso 2:
Danda rine huremu hwe 1 kg riri pamusoro petafura rinodhonzwa nguva nenguva kuitira kuti danda rifambe nekumhanya kwakafanana. Kana danda richifamba nekumhanya kwakafanana, dynamometer inoratidza nhamba 1 N. Kana kukurumidza kwegiravhiti = 10 m/s 2 , sarudza (a) hukuru hwesimba rekukweshana kwekinetic (b) chiyero chekukweshana kwekinetic
Solution:
Inozivikanwa: m = 1 kg, g = 10 m/s 2 , F = 1 N, w = mg = 10 N
(a) f k
Kana danda richifamba nguva dzose kana kuti richifamba nekumhanya kwakafanana, hukuru hwesimba rekukweshana kwekinetic = hukuru hwesimba rekudhonza (enzanisa equation 1.6).
Saka 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
