Zitsanzo 4 za mafunso okhudza kugwiritsa ntchito malamulo a Newton poyendetsa bwino lift kapena elevator
1. Munthu wolemera makilogalamu 50 ali mu elevator. Kuthamanga chifukwa cha mphamvu yokoka = 10 m/s2Dziwani kukula kwa mphamvu yachibadwa yomwe pansi pa elevator imagwiritsira ntchito pa munthuyo ngati:
(a) chikepe chopanda phokoso
(b) elevator imatsika pansi pa liwiro losasintha
(c) chikepicho chimakwera mmwamba ndi liwiro la 5 m/s2
(d) chikepicho chimatsika ndi liwiro la 5 m/s2
(e) elevator yogwa kwaulere
Zokambirana
Ndizodziwika kuti :
Kulemera kwa munthu (m) = 50 kg
Kuthamanga chifukwa cha mphamvu yokoka (g) = 10 m/s2
Kulemera kwa munthu (w) = mg = (50)(10) = 500 Newtons
Yankhani :
(a) chikepe chopanda phokoso
Chikepe chili pamalo opumulira, palibe kuthamanga (a = 0)
Mphamvu yolunjika mmwamba ndi yabwino, mphamvu yolunjika pansi ndi yoipa.
(b) elevator imatsika pansi pa liwiro losasintha
Chikepe chimayenda pa liwiro losasintha, palibe kuthamanga (a = 0)
Mphamvu yolunjika mmwamba ndi yabwino, mphamvu yolunjika pansi ndi yoipa.
(c) chikepicho chimakwera mmwamba ndi liwiro la 5 m/s2
Chikepecho chimakwera mmwamba ndi liwiro la (a) la 5 m/s2
Mphamvu yomwe ili mbali imodzi ndi kayendetsedwe ka lift ndi yabwino, mphamvu yomwe ili mbali ina yosiyana ndi kayendetsedwe ka lift ndi yoipa.
N – w = ma
N = w + ma
N = 500 + (50)(5)
N = 500 + 250
N = 750 Newton
Kukula kwa mphamvu yachibadwa (N) ndi kofanana ndi kulemera (w), motero pamene chikepi chikupita mmwamba, thupi la munthu limamva lolemera. Mwa kuyankhula kwina, pamene chikepi chikupita mmwamba, kulemera kwa munthuyo kumawonjezeka. Ngati munthuyo akuyimirira pa sikelo, pamene chikepi chikupita mmwamba, sikeloyo idzawonetsa kuti kulemera kwa munthuyo ndi kwakukulu.
(d) chikepicho chimatsika ndi liwiro la 5 m/s2
Chikepe chimatsika ndi liwiro la (a) la 5 m/s2
Mphamvu yomwe ili mbali imodzi ndi kayendetsedwe ka lift ndi yabwino, mphamvu yomwe ili mbali ina yosiyana ndi kayendetsedwe ka lift ndi yoipa.
w – N = ma
N = w – ma
N = 500 – (50)(5)
N = 500 - 250
N = 250 Newton
Pamene elevator ikutsika, thupi la munthuyo limakhala lopepuka. Mwa kuyankhula kwina, pamene elevator ikutsika, kulemera kwa munthuyo kumawonjezeka. Ngati munthuyo akanakhala kuti wayima pa sikelo, pamene elevator ikutsika, sikeloyo ingasonyeze kulemera kochepa.
(e) elevator yogwa kwaulere
Chikepe chogwa mwaulere chimatanthauza kuti chikepe chimapita pansi, komwe kuthamanga kwa chikepe (a) = kuthamanga kwa mphamvu yokoka (g). Mwachitsanzo, g = 10 m/s2 ndiye a = 10 m/s2
Mphamvu yomwe ili mbali imodzi ndi kayendetsedwe ka lift ndi yabwino, mphamvu yomwe ili mbali ina yosiyana ndi kayendetsedwe ka lift ndi yoipa.
w – N = ma
N = w – ma
N = 500 – (50)(10)
N = 500 - 500
N = 0
Pamene elevator ili mu free fall, kulemera kwa munthuyo kumakhala zero. Mwa kuyankhula kwina, munthuyo angadzione ngati wopanda kulemera. Ngati munthuyo angayime pa sikelo, pamene elevator ikutsika pansi, sikeloyo ingasonyeze kuti kulemera kwake ndi zero. Vutoli likufanana ndi kukhala pamalo opanda mphamvu yokoka.
2. Dziwani kukula kwa mphamvu ya kukakamira pa chingwe chothandizira chokweza chokhala ndi kulemera kwa 2000 kg, ngati:
(a) chikepe chopanda phokoso
(b) chikepicho chimatsika ndi liwiro la 5 m/s2
(c) chikepicho chimakwera mmwamba ndi liwiro la 5 m/s2
(d) elevator yogwa kwaulere
Ganizirani kuti kuthamanga kwa mphamvu yokoka (g) = 10 m/s2
Zokambirana
Ndizodziwika kuti :
Kulemera kwa chonyamulira (m) = 2000 kg
Kuthamanga chifukwa cha mphamvu yokoka (g) = 10 m/s2
Kulemera kwa kukweza (w) = mg = (2000)(10) = 20.000 Newtons
Yankhani :
(a) chikepe chopanda phokoso
Chikepe chili pamalo opumulira, palibe kuthamanga (a = 0)
Mphamvu yolunjika mmwamba ndi yabwino, mphamvu yolunjika pansi ndi yoipa.
Pamene chokweza chilibe, mphamvu ya kukanikiza chingwe (T) = kulemera kwa chokweza (w) = 20.000 Newtons
(b) chikepicho chimatsika ndi liwiro la 5 m/s2
Chikepe chimatsika ndi liwiro la (a) la 5 m/s2
Mphamvu yomwe ili mbali imodzi ndi kayendetsedwe ka lift ndi yabwino, mphamvu yomwe ili mbali ina yosiyana ndi kayendetsedwe ka lift ndi yoipa.
w – T = ma
T = w – ma
T = 20.000 – (2000)(5)
T = 20.000 – 10.000
T = 10.000 Newtons
Chikepe chikatsika, mphamvu ya chingwe (T) imakhala yochepa kuposa pamene chikepe chikadali chokhazikika.
(c) chikepicho chimakwera mmwamba ndi liwiro la 5 m/s2
Chikepecho chimakwera mmwamba ndi liwiro la (a) la 5 m/s2
Mphamvu yomwe ili mbali imodzi ndi kayendetsedwe ka lift ndi yabwino, mphamvu yomwe ili mbali ina yosiyana ndi kayendetsedwe ka lift ndi yoipa.
T – w = ma
T = w + ma
T = 20.000 + (2000)(5)
T = 20.000 + 10.000
T = 30.000 Newtons
Chikepe chikakwera mmwamba, mphamvu ya kukanikiza chingwe (T) imakhala yayikulu kuposa chikepe chikaima pamalo amodzi.
(d) elevator yogwa kwaulere
Chikepe chogwa mwaulere chimatanthauza kuti chikepe chimapita pansi, komwe kuthamanga kwa chikepe (a) = kuthamanga kwa mphamvu yokoka (g). Mwachitsanzo, g = 10 m/s2 ndiye a = 10 m/s2
Mphamvu yomwe ili mbali imodzi ndi kayendetsedwe ka lift ndi yabwino, mphamvu yomwe ili mbali ina yosiyana ndi kayendetsedwe ka lift ndi yoipa.
w – T = ma
T = w – ma
T = 20.000 – (2000)(10)
T = 20.000 – 20.000
T = 0
Pamene elevator ili mu free fall, mphamvu ya chingwe (T) imakhala zero. Chifukwa mphamvu ya chingwe ndi yofanana ndi kulemera kwa elevator, pamene mphamvu ya chingwe ndi zero, kulemera kwa elevator kumawonekanso zero. Izi zikufanana ndi pamene chinthu chili mu vacuum yokoka kapena malo omwe palibe mphamvu yokoka.
[Chingerezi: Kugwiritsa ntchito lamulo la Newton loyendetsa mu elevator ]
3. Munthu wolemera makilogalamu 60 ali mu elevator yomwe ikuyenda pansi ndi kuthamanga kwa 3 ms -2 . Ngati kuthamanga chifukwa cha mphamvu yokoka ndi 10 ms -2 , ndiye kuti mphamvu yachibadwa yomwe pansi pa elevator imaperekedwa pa munthuyo ndi...
A. 180 N
B. 200 N
C. 340 N
D. 420 N
E. 600 N
Zokambirana
Amadziwika kuti:
Kulemera (m) = 60 kg
Kuthamanga kwa munthu ndi elevator (a) = 3 m/s2
Kuthamanga chifukwa cha mphamvu yokoka (g) = 10 m/s2
Mphamvu yokoka (w) = mg = (60)(10) = 600 Newtons
Anafunsa: mphamvu yachibadwa (N)
Yankho:
Pali mphamvu ziwiri zomwe zimagwira ntchito pa munthu yemwe ali mu elevator, zomwe ndi mphamvu yokoka (w) ndi mphamvu yachibadwa yomwe pansi pa elevator pa munthuyo (N). Pali kuchuluka kwa ma vector atatu, komwe ndi mphamvu yokoka, mphamvu yachibadwa, ndi kufulumizitsa elevator, komwe mphamvu yokoka imatsogozedwa pansi, mphamvu yachibadwa imatsogozedwa mmwamba, ndipo kufulumizitsa elevator kumatsogozedwa pansi. Kuchuluka kwa vector yolunjika pansi kumasankhidwa kukhala ndi chizindikiro chabwino ndipo kuchuluka kwa vector yolunjika mmwamba kumasankhidwa kukhala ndi chizindikiro choipa.
∑F = ma
w – N = (60)(3)
600 – N = 180
N = 600 - 180
N = 420 Newton
Yankho lolondola ndi D.
4. Reza, wolemera makilogalamu 40, ali mu elevator yomwe ikukwera mmwamba. Ngati mphamvu ya pansi pa elevator pamapazi a Reza ndi 520 N ndipo kuthamanga chifukwa cha mphamvu yokoka ndi 10 ms -2 , ndiye kuti kuthamanga kwa elevator ndi...
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
Zokambirana
Amadziwika kuti:
Kulemera (m) = 40 kg
Mphamvu yachibadwa (N) = 520 N
Kuthamanga chifukwa cha mphamvu yokoka (g) = 10 m/s2
Mphamvu yokoka (w) = mg = (40)(10) = 400 N
Anafunsa: Kuthamanga kwa elevator
Yankho:
∑F = ma
400 – 520 = (40)(a)
-120 = (40)(a)
a = -120/40
a = -3 m/s2
Kuthamanga kwa elevator ndi 3 m/s2Chizindikiro chotsutsa chimatanthauza kuti elevator ikukwera mmwamba.
Yankho lolondola ndi E.
Gwero la funso:
Mafunso a National Examination Physics a Senior High School/Vocational High School
