Imithetho kaNewton

Imithetho kaNewton yokunyakaza inezintathu, okungukuthi umthetho wokuqala kaNewton, umthetho wesibili kaNewton kanye nomthetho wesithathu kaNewton.

Umthetho Wokuqala KaNewton

UMthetho Wokuqala KaNewton uthi yonke into ephumule izohlala iphumule noma yonke into ehamba emgqeni oqondile ngesivinini esingaguquki izoqhubeka nokuhamba emgqeni oqondile ngesivinini esingaguquki uma amandla aphelele asebenza entweni engu-zero.

Cabanga ngento ekuzungezile, isibonelo itafula noma idwala noma noma iyiphi into. Itafula eliphumule lizohlala liphumule uma lingashukunyiswa noma linganikezwa amandla angaphandle njengokucindezela noma ukudonsa amandla. Ngokufanayo, nezinye izinto eziphumule. Awekho yini amandla asebenza etafuleni noma edwaleni noma kunoma iyiphi enye into ephumule? Kukhona amandla asebenza entweni, kodwa isamba sawo wonke amandla asebenza entweni noma amandla aphelele alingana no-zero. Amandla asebenza entweni ephumule ebusweni beplanethi efana noMhlaba adonsela phansi (w) kanye amandla avamile (N). Isiqondiso samandla adonsela phansi siqonde phansi enkabeni yomhlaba, isiqondiso samandla avamile siqonde phezulu. Ubukhulu bala mandla amabili buyafana kodwa buphambene ngendlela ephambene, ngakho-ke amandla aphelele alingana no-zero.

Kuthiwani ngento ehamba emgqeni oqondile ngesivinini esingaguquki? Ukuze kucaciswe lokhu, ake sithi ucindezela into, njengengcezu yensimbi, phansi. Ngemva kokusunduzwa, ingcezu yensimbi iyehla bese ima ngenxa yokuba khona kwayo. amandla okungqubuzanaUkuze izingcezu zensimbi zihambe ibanga elide noma ngaphezulu, kufanele ulungise ubuso bephansi kanye nobuso bezingcezu zensimbi. Uma ubuso bephansi kanye nobuso bezingcezu zensimbi bubushelelezi, kulapho izingcezu zensimbi zihamba ibanga elide. Uma ubuso bephansi bubushelelezi ngokuphelele futhi kungekho ukungqubuzana, izingcezu zensimbi zizoqhubeka zihamba futhi zingami. Awekho yini amandla asebenza engxenyeni yensimbi ehamba phezu kobuso bephansi obubushelelezi ngokuphelele? Kukhona amandla asebenza ezingcezu zensimbi, okungukuthi amandla adonsela phansi kanye namandla ajwayelekile. Lawa mandla amabili asebenza ohlangothini oluqondile futhi awathinti ukunyakaza kwezingcezu zensimbi ohlangothini oluvundlile uma phansi lubushelelezi ngokuphelele.

Umthetho Wesibili KaNewton

Umthetho Wesibili kaNewton uthi uma amandla aphelele asebenza entweni engekho ziro, into izoshesha. Ubukhulu bokusheshisa buhambisana nobukhulu bamandla aphelele futhi buhambisana nobunzima bento. Isiqondiso sokusheshisa sifana nesiqondiso samandla aphelele.

ΣF = ma(1.2)

Incazelo: ΣF = amandla aphelele (kg m/s²), m = isisindo (kg), a = ukusheshisa (m/s²)

Isibalo 1.2 siyisitatimende sezibalo somthetho wesibili kaNewton.

Uma ubukhulu bokusheshisa bulingana no-zero (a = 0) khona-ke i-equation 1.2 iyashintsha ibe yi-equation 1.1. Ngakho-ke umthetho wokuqala kaNewton uyisibonelo esikhethekile somthetho wesibili kaNewton.

Ngokusekelwe ku-equation 1.2, kuphethwa ngokuthi lapho amandla emakhulu, kulapho ukusheshisa kuba kukhulu khona. Ngokuphambene nalokho, lapho isisindo siba sikhulu, ukusheshisa kuba kuncane. Ubudlelwano phakathi kwamandla, isisindo, kanye nokusheshisa buqondwa kangcono ngemva kokwenza izivivinyo ezihlobene nalokhu. Olunye uvivinyo olungenziwa ukuhlolwa kokusheshisa isitimela esishintshashintshayo ezitimeleni kusetshenziswa isisindo esiwa ngokukhululeka. Sebenzisa i-ticker timer ukuze unqume ukusheshisa kwesitimela.

Umthetho Wesithathu KaNewton

Umthetho wesithathu kaNewton uthi uma into 1 isebenzisa amandla entweni 2, khona-ke into 2 isebenzisa amandla entweni 1. Ubukhulu bamandla womabili buyafana kodwa isiqondiso samandla womabili siphambene. Amandla elilodwa libizwa ngokuthi isenzo, elinye amandla libizwa ngokuthi ukusabela (amandla okusabela-isenzo).

F_okuphambene = – F_ukusabela                                      (1.3)

Isibalo 1.3 siyisitatimende sezibalo somthetho wesithathu kaNewton. Uphawu olubi kusibalo 1.3 lubonisa isiqondiso samandla.

Yenza ucwaningo ukuze uqonde kangcono umthetho wesithathu kaNewton. Uma une-skateboard, cindezela odongeni umi phezu kwalo. Ngemva kokucindezela odongeni, i-skateboard iya emuva. Ukucindezela kwakho kuya phambili, kuyilapho i-skateboard iya emuva. Lokhu kukhombisa ukuthi udonga nalo luyakucindezela. Uma ucindezela odongeni, ngesikhathi esifanayo, udonga nalo luyakucindezela. Amandla akho okusunduza asebenza odongeni, kuyilapho amandla okusunduza odongeni esebenza kuwe. Amandla amabili ayalingana ngobukhulu kodwa aphambene ngendlela eqondile. Ungabiza amandla elilodwa ngokuthi isenzo kanti elinye ngokuthi ukusabela.

Olunye uvivinyo ongalwenza ukuqhumisa ibhaluni lerabha, bese ulikhulula ngemva kokuba seligcwele umoya. Ngemva kokulikhulula, ibhaluni "liyandiza." Indlela yokuhamba kwebhaluni iphambene nendlela umoya ophuma ngayo ebhaluni. Lokhu kungachazwa kanjani? Lapho umlomo webhaluni ukhishwa, ibhaluni lisunduza umoya. Ngesikhathi esifanayo, umoya uphinde usunduze ibhaluni. Ukusunduza komoya kubangela ukuba ibhaluni lindize. Ukusunduza kwebhaluni kusebenza emoyeni, kanti ukusunduza komoya kusebenza ebhaluni. Amandla amabili ayalingana ngobukhulu kodwa aphambene ngendlela ehlukile.

Isibonelo sezinkinga

1. Kunezinto ezingu-4, ubhanana = 4 kg, incwadi = 0,8 kg, ibhola lomnqakiswano = 3,5 kg, umango = 1,2 kg. Ibhasikidi lidonswa ngamandla angu-30 N endaweni eyisicaba elukhuni (μ = 0,4). Ukuze ibhasikidi lihambe kahle (isisindo sebhasikidi asinakwa), into okumele ifakwe ebhasikidini...

Ingxoxo

Kuyaziwa:

Isisindo sikabhanana (m₁) = 4 kg

Isisindo sencwadi (m₂) = 0,8 kg

Isisindo sebhola (m₃) = 3,5 kg

Isisindo sikamango (m₄) = 1,2 kg

Amandla okudonsa (F) = 30 N

I-coefficient yokungqubuzana okuqinile (μ_s= = 0,4

Ukusheshisa ngenxa yamandla adonsela phansi (g) = 10 m/s²

Unganaki isisindo sebhasikidi

Amandla okungqubuzana aqinile (f)_s) isebenza lapho into isaphumule futhi isizohamba, kanti ukungqubuzana kwe-kinetic kusebenza lapho into ihamba.

Kubuziwe: Isisindo sento

Impendulo:

Ibhasikidi lizohamba ngqo lapho ubukhulu bamandla okudonsa (F) = ubukhulu bamandla okungqubuzana angaguquki (f)_s).

Bala ubukhulu bamandla okungqubuzana okungaguquki (f)_s):

f_s = μ_s N = μ_s w = μ_s mg = (0,4)(m)(10)

f_s = 4m

Ibhasikidi eliqondile lizohamba:

F = f_s

30 = 4m

m = 30/4

m = 7,5 kg

Isisindo sikabhanana 4 kg + isisindo sebhola 3,5 kg = 7,5 kg

Izinto okumele zifakwe ebhasikidini ubhanana namabhola.

2. Umbuzo Wokuhlolwa Kazwelonke We-SMA/MA We-Fiziksi We-2014/2015 No. 5

Izinto A ezinesisindo esingu-6 kg kanye no-B ezinesisindo esingu-4 kg zixhunywe ngentambo bese zidonswa ngamandla F = 60 N njengoba kuboniswe esithombeni esilandelayo.

Uma uhlelo luhamba kanye ne-coefficient of kinetic friction phakathi kwe-indawo ephansi enezinto zombili 0,5 (tg θ = 3/4), kanye no-g = 10 ms^-2, bese kuba kukhuluyebo, ukucindezeleka kwentambo engu-T exhumanisa izinto ezimbili….

A. 28,8 N

B. 30,0 N

C. 39,6 N

D. 48,0 N

E. 50,0 N

Ingxoxo

Kuyaziwa ukuthi:

Isisindo sento A (m_A) = 6 kg

Isisindo sento B (m_B) = 4 kg

Amandla okudonsa (F) = 60 Newton

I-coefficient yokungqubuzana kwe-kinetic phakathi kwento kanye nephansi (μ_k= = 0,5

Ukusheshisa ngenxa yamandla adonsela phansi (g) = 10 m/s²

I-Tangent θ = 3/4

Kubuziwe: Ingabe inkulu?yebo intambo yokucindezela u-T

Impendulo:

Ingxenye evundlile yamandla F:

F_x = F cos θ

F_x = (60)(4/5) = (4)(12) = 48 N

Ingxenye eqondile yamandla F:

F_y = F isono θ

F_y = (60)(3/5) = (3)(12) = 36 N

Amandla ajwayelekile ento A:

N_A = w_A = m_A g = (6)(10) = 60 N

Amandla ajwayelekile ento B:

N_B +F_y - w_B = 0

N_B +F_y = w_B

N_B = w_B - F_y = m_B g – F_y = (4)(10) – 36 = 40 – 36 = 4 N

Amandla okungqubuzana kwe-kinetic phakathi kwento A kanye nephansi:

f_kA = μ_k N_A = (0,5)(60) = 30 N

Amandla okungqubuzana kwe-kinetic phakathi kwento B kanye nephansi:

f_kB = μ_k N_B = (0,5)(4) = 2 N

Bala ukusheshisa kwezinto zombili:

ΣF = ma

F_x – T + T – f_kB - f_kA = (m_A +m_B) futhi

Amandla okucindezela ku-string T anobukhulu obufanayo ngobude be-string futhi anohlangothi oluphambene ngakho asuswa ku-equation.

F_x - f_kB - f_kA = (m_A +m_B) futhi

48 – 2 – 30 = (6 + 4) a

16 = 10 a

a = 16/10

a = 1,6 m/s²

Bala amandla okucindezela entambo T:

Cabanga ngento A. Amandla asebenza entweni A ohlangothini oluvundlile (oluvundlile) amandla okucindezela intambo (T) aqondiswe kwesokudla kanye namandla okucindezela i-kinetic (f)._kA) okungakwesokunxele.

ΣF = ma

T_A - f_kA = m_A a

T_A - 30 = (6)(1,6)

T_A - 30 = 9,6

T_A = 9,6 + 30 = 39,6 N

Cabanga ngento B. Amandla asebenza entweni B ohlangothini oluvundlile (oluvundlile) angamandla F_x okuqondiswe kwesokudla, amandla okungqubuzana kwe-kinetic (f)_kB) kanye namandla okucindezela intambo (T) aqondiswe kwesobunxele.

ΣF = ma

F_x - f_kB - T_B = m_B a

48 – 2 – T_B = (4)(1,6)

46 - T_B = 6,4

46 – 6,4 = T_B

T_B = I-39,6 N

Ngakho-ke amandla okucindezela entanjeni asebenza entweni A (T)_A) = amandla okucindezela entanjeni asebenza entweni B (T_B) = 39,6 N.

Impendulo efanele ngu-C.

3. Umbuzo Wokuhlolwa Kazwelonke We-SMA/MA We-Fiziksi We-2014/2015 Inombolo 5

Bheka isithombe esilandelayo!

Ngenxa yamandla u-F, uhlelo lwezinto luyahamba. Uma phansi kuqinile futhi i-coefficient of kinetic friction phakathi kwamabhulokhi amabili kanye nephansi ingu-0,2, kuyini ukusheshisa okubonwa yizinto ezimbili? (cos 37^o = 0,8, isono 37^o = 0,6)

A. 2,6 ms^-2

B. 4,0 ms^-2

C. 5,2 ms^-2

D. 7,8 ms^-2

E. 10,2 ms^-2

Ingxoxo

Kuyaziwa ukuthi:

Isisindo sento A (m_A) = 4 kg

Isisindo sento B (m_B) = 2 kg

Amandla okudonsa (F) = 30 Newton

I-coefficient yokungqubuzana kwe-kinetic phakathi kwento kanye nephansi (μ_k= = 0,2

Ukusheshisa ngenxa yamandla adonsela phansi (g) = 10 m/s²

ibe 37^o = 0,8

ngaphandle 37^o = 0,6

Kubuziwe: Yikuphi ukusheshisa okwenziwa yizinto zombili?

Impendulo:

Ingxenye evundlile yamandla F:

F_x = F cos θ

F_x = (30)(0,8) = 24 N

Ingxenye eqondile yamandla F:

F_y = F isono θ

F_y = (30)(0,6) = 18 N

Amandla ajwayelekile ento A:

N_A = w_A = m_A g = (4)(10) = 40 N

Amandla ajwayelekile ento B:

N_B +F_y - w_B = 0

N_B +F_y = w_B

N_B = w_B - F_y = m_B g – F_y = (2)(10) – 18 = 20 – 18 = 2 N

Amandla okungqubuzana kwe-kinetic phakathi kwento A kanye nephansi:

f_kA = μ_k N_A = (0,2)(40) = 8 N

Amandla okungqubuzana kwe-kinetic phakathi kwento B kanye nephansi:

f_kB = μ_k N_B = (0,2)(2) = 0,4 N

Bala ukusheshisa kwezinto zombili:

ΣF = ma

F_x - f_kB - f_kA = (m_A +m_B) futhi

24 – 0,4 – 8 = (4 + 2) a

15,6 = 6 a

a = 15,6/6

a = 2,6 m/s²

Impendulo efanele ngu-A.