Giai Dong nang quay: Momen dong Suy Wa = — I©' liTdng: L = Ico ^ = I^co\ Wd = — 21' Vdy chon dap an C Cdu 59: Mot dong ho chuyen dong t h i n g deu v6i toe v = 0,8c (vdfi e la toe anh sang chan khong) Sau 12 phut (tinh theo dong ho do), dong ho chay cham hofn dong ho g i n vdri quan sat vien dufng yen la: A 4,8 phut B 20 phut C phut D 7,2 phut ra: Giai Vi V = 0,8c nen J l - \ ^ - , = 0,6 Taco: At = ^ ^ ^ ^ = — - = 20 0,6 rv ThcJi gian chay cham hofn: t = At-Atg = 20 - 12 = (phut) Vdy chgn dap an C Cdu 60: Mot \Ac vat li la m6t vat r^n c6 khoi lilgrng m = kg dao dong dieu hoa vdri chu ki T = 0,5s Khoang each tCf t a m cua vat den true quay cua no la d = 20 cm Lay g = 10 m/s^ va =10 Momen quan tinh cua vat doi v6i true quay la: A 0,025kg.ml B 0,64kg.ml C 0,05kg.m' D 0,5kg.ml GiSi Taco: T = 2;r^ \mgd Vdy chon dap an C Giai Chi tiSi : '• 71 t = -:^ = ^ 271 2TC T Y = - = l , - ' s = > T = 12.10-^8 Thc/i gian de d i e n t l c h g i a m tii cUc dai xuong m o t nufa: t = ^ = i = I = 2.10-s CO 27t T Vdy chon dap an A Giii Chi ti6t dS thi T S D H , C D M6n V$t I 107 ... -:^ = ^ 27 1 2TC T Y = - = l , - ' s = > T = 12. 10-^8 Thc/i gian de d i e n t l c h g i a m tii cUc dai xuong m o t nufa: t = ^ = i = I = 2. 10-s CO 27 t T Vdy chon dap an A Giii Chi ti6t dS thi T... g i a m tCr gia t r i ciic dai xuong m o t nufa gia t r i la: A 2. 10-^s B 3.10-''s C e.lO-^s D 12. 10-*s Giai Ta c6: 2C 2C •" V2 ' T h d i gian nang liicfng dien g i a m tCf ctfc d a i xuong m... xay r a cong hiidng hay i.^ = 27 1 V L C ' M a t khac ufng v d i fi t a c6: Z, = — Zp 27 if,L - —.—^— o f , =-f,^ f, = Vdy chgn dap an A 106 Gi&i Chi m (i6 thi T S D H , C D M6n V * t l(