1. Umuntu usesiliftini esikhuphuka ngesivinini esingaguquki . Isisindo somuntu singama-800 N. Intambo yelifti iyaphuka ngokushesha, ngakho-ke i-lifti iyawa. Thola amandla ajwayelekile asetshenziswa phansi kwe-lifti kumuntu ngaphambi nangemva kokuba intambo ye-lifti iphuke.
A. 800 N kanye no-0
B. 800 N kanye no-800 N
C. 1600 N kanye no-0
D. 1600 N kanye no-800 N
Kwaziwa:
Isisindo (w) = 800 Newton
Okufunwayo: Amandla avamile (N)
Isixazululo:
Ngaphambi kokuba intambo yelifti iphuke
Uma umuntu emi phansi e-lifti, isisindo sisebenza kumuntu lapho isiqondiso somuntu siphansi. Lowo muntu uphumule ngakho kumele kube namandla avamile asebenza kumuntu, lapho isiqondiso samandla avamile siphezulu futhi ubukhulu bamandla avamile bufana nobukhulu besisindo.
Ngoba umuntu uphumule ekheshini futhi ikheshi lihamba ngesivinini esingaguquki (cha ukusheshisa), ngakho-ke awekho amandla okumthatha umuntu.
∑F = 0
N – w = 0
N = w
N = 800 Newton
Ngemva kokuba intambo yelifti iphuke
Ngemva kokuba intambo yelifti iphuke, ilifti nomuntu bawela ndawonye ngokukhululeka , lapho ubukhulu kanye nesiqondiso sokusheshisa kwabo kufana nokusheshisa ngenxa yamandla adonsela phansi. Akukho mandla avamile kumuntu.
Impendulo eyiyo ngu-A.
2. Ibhlokhi elinesisindo esingamagremu angu-20 lihamba ngesivinini esingaguquki phansi elivundlile elingaguquki ngesivinini esingaguquki uma kukhona amandla angaphandle angu-2 N asebenza ebhlokini. Thola ubukhulu bamandla okungqubuzana atholwa yibhlokhi.
A. 0.3 N
B. 1.4 N
C. 2.0 N
D. 3.6 N
Kwaziwa:
Isisindo (m) = amagremu angu-20
Amandla (F) = 2 Newton
Okufunwayo: Ubukhulu bamandla okungqubuzana abonwa yibhlokhi.
Isixazululo:
Ngokusekelwe emthethweni wokuqala kaNewton wokunyakaza, uma ibhloko lihamba ngesivinini esingaguquki, khona-ke ibhloko alinaso isivinini. Ibhloko lihamba ngesivinini esingaguquki, futhi akukho ukusheshisa uma:
– Ubukhulu bamandla okungqubuzana (F fric ) bufana nobukhulu bamandla angaphandle (F)
– Amandla okungqubuzana (F fric ) aphambene namandla angaphandle (F)
Sebenzisa umthetho wokuqala kaNewton wokunyakaza:
∑ F = 0
F – F fric = 0
F = F fric
F fric = 2 Newton
Impendulo efanele ithi C.
3. Indiza ethambekele kahle enobude obungu-0.6 m kanye nokuphakama okungu-0.4 m. Ibhlokhi enesisindo esingu-1350 N izokhuphukela phezulu isebenzisa indiza ethambekele. Thola ubukhulu bamandla adingekayo ukuhambisa ibhlokhi.
A. 100 N
B. 300 N
C. 600 N
D. 900 N
Kwaziwa:
Isisindo sebhulokhi (w) = 1350 Newtons
i-hyp = 0.6 m
opp = 0.4 m
Okufunwayo: Amandla amancane
Isixazululo:
i-hyp = ac = 0.6 m
opp = bc = 0.4 m
Isono θ = bc / ac = 0.4 / 0.6 = 4/6 = 2/3
Ngokusekelwe emthethweni wokuqala kaNewton wokunyakaza, ibhloko liqala ukunyuka bese kuthi amandla angaphandle (F) okungenani afane nengxenye evundlile yesisindo (w x ).
∑ F = 0
F – w x = 0
F = w x
Uma u-F = w x , khona-ke into iqala ukukhuphukela phezulu ngesivinini esingaguquki.
w x = w isono θ = (1350)(2/3) = (2)(450) = 900 Newtons
Impendulo efanele ngu-D.
4. Amandla amathathu, F 1 = 22 N, F 2 = 18 N kanye F 3 = 40 N asebenza ebhulokini. Yisiphi isibalo esichaza umthetho wokuqala kaNewton.
Isixazululo:
Umthetho wokuqala kaNewton: Amandla aphelele (ΣF) = 0.
A. F 1 + F 2 – F 3 = 22 N + 18 N – 40 N = 40 N – 40 N = 0
B. F 2 + F 3 – F 1 = 18 N + 40 N – 22 N = 58 N – 22 N = 36 N (ngakwesokudla)
C. F 2 + F 3 – F 1 = 18 N + 40 N – 22 N = 58 N – 22 N = 36 N (ngakwesokudla)
D. F 1 + F 3 – F 2 = 22 N + 40 N – 18 N = 62 N – 18 N = 44 N (ngakwesobunxele)
