Kawm txog Cov Lus Nug Piv Txwv ntawm Center of Gravity
Nkag Siab Txog Qhov Chaw Ntawm Lub ntiajteb txawj nqus
Ib yam khoom khov kho raug suav hais tias yog tsim los ntawm ntau yam khoom me me vim qhov no lub zog gravitational ua haujlwm rau txhua yam ntawm cov khoom me me no. Hauv lwm lo lus, txhua yam khoom me me muaj nws qhov hnyav. Lub hauv paus ntawm lub ntiajteb txawj nqus ntawm ib yam khoom yog ib qho chaw nyob rau ntawm lossis ze ntawm yam khoom uas qhov hnyav ntawm txhua qhov ntawm yam khoom tau sib sau ua ke.
Yog tias ib yam khoom zoo ib yam (qhov ceev ntawm qee yam khoom zoo ib yam lossis yam khoom muaj cov khoom zoo sib xws) thiab cov duab ntawm yam khoom yog sib npaug (piv txwv li plaub fab, plaub fab plaub fab, lub voj voog) ces qhov chaw nruab nrab ntawm lub ntiajteb txawj nqus ntawm yam khoom sib phim nrog qhov chaw nruab nrab ntawm qhov hnyav ntawm yam khoom uas nyob hauv nruab nrab ntawm yam khoom. Rau ib daim duab peb ceg, qhov chaw nruab nrab ntawm qhov hnyav nyob ntawm 1/3 h, qhov twg h = qhov siab ntawm daim duab peb ceg.
Lub hauv paus ntawm lub ntiajteb txawj nqus
Yog tias cov duab ntawm yam khoom yog symmetrical thiab yam khoom yog homogeneous ces qhov chaw ntawm lub ntiajteb txawj nqus coincides nrog qhov chaw ntawm pawg ntawm yam khoom, qhov twg qhov chaw ntawm lub ntiajteb txawj nqus thiab qhov chaw nruab nrab ntawm qhov hnyav nyob hauv nruab nrab ntawm cov khoom. Ntawm qhov tod tes, yog tias cov khoom yog homogeneous tab sis tsis symmetrical, qhov chaw ntawm cov khoom qhov chaw nruab nrab ntawm lub ntiajteb txawj nqus tuaj yeem txiav txim siab siv cov qauv hauv qab no:
Cov Ntaub Ntawv:
x = nruab nrab ntawm cov khoom ntawm x-axis, y = nruab nrab ntawm cov khoom ntawm y-axis, A = thaj tsam ntawm cov khoom.
Piv txwv txog teeb meem
1. 2011/2012 Cov Lus Nug Txog Kev Xeem Hauv Tebchaws C61 No.12
Saib daim duab ntawm lub dav hlau sib npaug! Qhov chaw ntawm qhov chaw nruab nrab ntawm lub ntiajteb txawj nqus ntawm lub cev khoom hauv qhov kev taw qhia y-axis los ntawm qhov taw tes Q yog…
A. 1,00 cm
B. 1,75 cm
C. 2,00 cm
D. 3,00 cm
E. 3,25 cm
Kev Sib Tham
Faib cov khoom ua ob ntu, ntu 1 = lub duab plaub fab, ntu 2 = daim duab peb ceg.
A1 = (12,5)(2) = 25
A2 = ½ (12,5-2,5)(3) = ½ (10)(3) = (5)(3) = 15
y1 = ½ (2) = 1
y2 = 1/3 (3) + 2 = 1 + 2 = 3
Cov kev sib koom ua ke ntawm qhov chaw ntawm lub ntiajteb txawj nqus ntawm cov khoom ntawm y-axis:
Point Q = qhov dub nyob ntawm lub hauv paus ntawm qhov chaw ntawm yam khoom.
Cov lus teb yog B.
2. 2011/2012 Cov Lus Nug Txog Kev Xeem Hauv Tebchaws A81 No.12
Qhov chaw ntawm qhov chaw nruab nrab ntawm lub ntiajteb txawj nqus ntawm daim duab dav hlau raws li pom hauv daim duab ntawm sab ntawm x-axis yog ...
A. 4,5 cm
B. 4 cm
C. 3,5 cm
D. 3 cm
E. 2 cm
Kev Sib Tham
Faib cov khoom ua ob ntu, ntu 1 = lub duab plaub fab, ntu 2 = daim duab peb ceg.
A1 = (6-0)(3-0) = (6)(3) = 18
A2 = ½ (6-3)(6-3) = ½ (3)(3) = 4,5
y1 = ½ (3) = 1,5
y2 = 1/3 (6-3) + 3 = 1/3 (3) + 3 = 1 + 3 = 4
Cov kev sib koom ua ke ntawm qhov chaw ntawm lub ntiajteb txawj nqus ntawm cov khoom ntawm y-axis:
Cov lus teb yog yog E.
3. Cov Lus Nug Txog Kev Xeem Hauv Tebchaws Xyoo 2018
Ua tib zoo mloog cov lus hauv qab no:
(1) Rov ua cov txheej txheem ntawm kev txiav txim siab kab ntawm daim ntawv los ntawm ntau qhov chaw dai, thiab cim qhov kev sib tshuam ntawm ob kab ua qhov chaw nruab nrab ntawm lub ntiajteb txawj nqus ntawm daim ntawv.
(2) Khi cov xov kawg rau ntawm rab koob thiab hnyav thiab muab rab koob lo rau hauv daim ntawv.
(3) Kos ib txoj kab raws cov teev ntawm daim ntawv.
(4) Kos cov ntsiab lus raws txoj xov ntawm daim ntawv.
(5) dai daim ntawv los ntawm kev tuav lub hauv paus ntawm rab koob
Txhawm rau txiav txim siab qhov chaw ntawm qhov chaw nruab nrab ntawm lub ntiajteb txawj nqus ntawm daim ntawv tsis sib xws, cov kauj ruam raug yog ...
Kev Sib Tham
Cov kauj ruam raug yog 2, 5, 4, 3, 1.
