Izibonelo ezi-4 zemibuzo mayelana nokusetshenziswa kwemithetho kaNewton ekuhambeni okuqondile kwe-lift noma i-lifti
1. Umuntu onesisindo esingama-50 kg usesiliftini. Ukusheshisa ngenxa yamandla adonsela phansi = 10 m/s2Thola ubukhulu bamandla avamile asetshenziswa yiphansi le-lifti kumuntu uma:
(a) ilifti ethule
(b) ilifti yehla ngesivinini esingaguquki
(c) ilifti ikhuphukela phezulu ngesivinini esingu-5 m/s2
(d) ilifti yehla ngesivinini esingu-5 m/s2
(e) ilifti yokuwa yamahhala
Ingxoxo
I-Diketahui :
Isisindo somuntu (m) = 50 kg
Ukusheshisa ngenxa yamandla adonsela phansi (g) = 10 m/s2
Isisindo somuntu (w) = mg = (50)(10) = 500 Newtons
Jawab :
(a) ilifti ethule
Ilifti iphumule, akukho ukusheshisa (a = 0)
Amandla aqondiswe phezulu alungile, amandla aqondiswe phansi alungile.
(b) ilifti yehla ngesivinini esingaguquki
Ilifti ihamba ngesivinini esingaguquki, akukho ukusheshisa (a = 0)
Amandla aqondiswe phezulu alungile, amandla aqondiswe phansi alungile.
(c) ilifti ikhuphukela phezulu ngesivinini esingu-5 m/s2
Ilifti iya phezulu ngesivinini (a) esingu-5 m/s2
Amandla aqondene nokunyakaza kwe-lift alungile, amandla aqondene nokunyakaza kwe-lift alungile.
N – w = ma
N = w + ma
N = 500 + (50)(5)
N = 500 + 250
N = 750 Newton
Ubukhulu bamandla avamile (N) bulingana nesisindo (w), ngakho-ke lapho ilifti inyukela phezulu, umzimba womuntu uzizwa usinda. Ngamanye amazwi, lapho ilifti inyukela phezulu, isisindo esibonakalayo somuntu siba sikhulu. Uma umuntu emi esikalini, lapho ilifti inyukela phezulu, isikali sizobonisa ukuthi isisindo somuntu sikhulu.
(d) ilifti yehla ngesivinini esingu-5 m/s2
Ilifti yehla ngesivinini (a) esingu-5 m/s2
Amandla aqondene nokunyakaza kwe-lift alungile, amandla aqondene nokunyakaza kwe-lift alungile.
w – N = ma
N = w – ma
N = 500 – (50)(5)
N = 500 – 250
N = 250 Newton
Njengoba ilifti yehla, umzimba womuntu uzizwa ulula. Ngamanye amazwi, njengoba ilifti yehla, isisindo somuntu esibonakalayo siyanda. Uma umuntu emi esikalini, njengoba ilifti yehla, isikali sizobonisa isisindo esiphansi.
(e) ilifti yokuwa yamahhala
I-lifti ewela ngokukhululekile isho ukuthi i-lifti iyehla, lapho ukusheshisa kwe-lifti (a) = ukusheshisa kwamandla adonsela phansi (g). Isibonelo, g = 10 m/s2 bese u-a = 10 m/s2
Amandla aqondene nokunyakaza kwe-lift alungile, amandla aqondene nokunyakaza kwe-lift alungile.
w – N = ma
N = w – ma
N = 500 – (50)(10)
N = 500 – 500
N = 0
Uma ilifti ikwi-free fall, isisindo somuntu esibonakalayo singu-zero. Ngamanye amazwi, umuntu ubezozibona engenasisindo. Uma umuntu emi esikalini, njengoba ilifti yehla, isikali besizobonisa ukuthi isisindo sakhe singu-zero. Lesi simo sifana nokuba sendaweni engenamandla adonsela phansi.
2. Nquma ubukhulu bamandla okucindezela ekhebula lokusekela lokuphakamisa elinesisindo esingu-2000 kg, uma:
(a) ilifti ethule
(b) ilifti yehla ngesivinini esingu-5 m/s2
(c) ilifti ikhuphukela phezulu ngesivinini esingu-5 m/s2
(d) ilifti yokuwa yamahhala
Cabanga ngokusheshisa okubangelwa amandla adonsela phansi (g) = 10 m/s2
Ingxoxo
I-Diketahui :
Isisindo sokuphakamisa (m) = 2000 kg
Ukusheshisa ngenxa yamandla adonsela phansi (g) = 10 m/s2
Isisindo sokuphakamisa (w) = mg = (2000)(10) = 20.000 Newtons
Jawab :
(a) ilifti ethule
Ilifti iphumule, akukho ukusheshisa (a = 0)
Amandla aqondiswe phezulu alungile, amandla aqondiswe phansi alungile.
Uma i-lift imile, amandla okucindezela entanjeni (T) = isisindo se-lift (w) = ama-Newton angu-20.000
(b) ilifti yehla ngesivinini esingu-5 m/s2
Ilifti yehla ngesivinini (a) esingu-5 m/s2
Amandla aqondene nokunyakaza kwe-lift alungile, amandla aqondene nokunyakaza kwe-lift alungile.
w – T = ma
T = w – ma
T = 20.000 – (2000)(5)
T = 20.000 – 10.000
T = 10.000 Newton
Uma ilifti yehla, amandla okucindezela entanjeni (T) aba mancane kunalapho ilifti inganyakazi.
(c) ilifti ikhuphukela phezulu ngesivinini esingu-5 m/s2
Ilifti iya phezulu ngesivinini (a) esingu-5 m/s2
Amandla aqondene nokunyakaza kwe-lift alungile, amandla aqondene nokunyakaza kwe-lift alungile.
T – w = ma
T = w + ma
T = 20.000 + (2000)(5)
T = 20.000 + 10.000
T = 30.000 Newton
Uma ilifti inyukela phezulu, amandla okucindezela entanjeni (T) aba makhulu kunalapho ilifti imile.
(d) ilifti yokuwa yamahhala
I-lifti ewela ngokukhululekile isho ukuthi i-lifti iyehla, lapho ukusheshisa kwe-lifti (a) = ukusheshisa kwamandla adonsela phansi (g). Isibonelo, g = 10 m/s2 bese u-a = 10 m/s2
Amandla aqondene nokunyakaza kwe-lift alungile, amandla aqondene nokunyakaza kwe-lift alungile.
w – T = ma
T = w – ma
T = 20.000 – (2000)(10)
T = 20.000 – 20.000
T = 0
Uma ilifti ikwi-free fall, ukucindezeleka entanjeni (T) kuba yi-zero. Ngenxa yokuthi ukucindezeleka entanjeni kulingana nesisindo selifti, uma ukucindezeleka entanjeni kungu-zero, isisindo selifti naso sibonakala siyi-zero. Lesi simo sifana nalapho into ikwi-vacuum edonsela phansi noma endaweni lapho kungekho khona amandla adonsela phansi.
[IsiNgisi: Ukusetshenziswa komthetho kaNewton wokunyakaza e-lifti ]
3. Umuntu onesisindo esingama-60 kg usesiliftini esihamba phansi ngesivinini esingu-3 ms -2 . Uma ukusheshisa ngenxa yamandla adonsela phansi kungu-10 ms -2 , khona-ke ubukhulu bamandla avamile asetshenziswa phansi kwesilifti kumuntu...
A. 180 N
B. 200 N
C. 340 N
D. 420 N
E. 600 N
Ingxoxo
Kuyaziwa ukuthi:
IMisa (m) = 60 kg
Ukusheshisa komuntu kanye ne-lifti (a) = 3 m/s2
Ukusheshisa ngenxa yamandla adonsela phansi (g) = 10 m/s2
Amandla adonsela phansi (w) = mg = (60)(10) = 600 amaNewton
Kubuziwe: amandla avamile (N)
Impendulo:
Kunamandla amabili asebenza kumuntu ose-lifti, okungukuthi amandla adonsela phansi (w) kanye namandla avamile asetshenziswa phansi kwe-lifti kumuntu (N). Kunezinhlobo ezintathu ze-vector, okungukuthi amandla adonsela phansi, amandla avamile, kanye nokusheshisa i-lifti, lapho amandla adonsela phansi eqondiswa phansi, amandla avamile eqondiswa phezulu, kanye nokusheshisa i-lifti kuqondiswa phansi. Inani le-vector eliqondiswe phansi likhethwa ukuthi libe nophawu oluhle kanti inani le-vector eliqondiswe phezulu likhethwa ukuthi libe nophawu olubi.
∑F = ma
w – N = (60)(3)
600 – N = 180
N = 600 – 180
N = 420 Newton
Impendulo efanele ngu-D.
4. UReza, onesisindo esingama-40 kg, usesiliftini esikhuphukayo. Uma amandla ephansi lesilifti ezinyaweni zikaReza engama-520 N futhi ukusheshisa ngenxa yamandla adonsela phansi kungu-10 ms -2 , khona-ke ukusheshisa kwesilifti...
A. 1,0 ms-2
B. 1,5 ms-2
C. 2,0 ms-2
D. 2,5 ms-2
E. 3,0 ms-2
Ingxoxo
Kuyaziwa ukuthi:
IMisa (m) = 40 kg
Amandla ajwayelekile (N) = 520 N
Ukusheshisa ngenxa yamandla adonsela phansi (g) = 10 m/s2
Amandla adonsela phansi (w) = mg = (40)(10) = 400 N
Kubuziwe: Ukusheshisa kwe-lifti
Impendulo:
∑F = ma
400 – 520 = (40)(a)
-120 = (40)(a)
a = -120/40
a = -3 m/s2
Ukusheshisa kwe-elevator kungu-3 m/s2Uphawu olunegethivu lusho ukuthi ilifti iyakhuphuka.
Impendulo efanele ngu-E.
Umthombo wombuzo:
Imibuzo Yefiziksi Yezivivinyo Zikazwelonke Zesikole Samabanga Aphezulu/Isikole Samabanga Aphezulu Sokufundela Umsebenzi
