APj = ^ n » U2 = V^U, = nU^ N, U Vay chgn dap an B Cdu 46: M a c h chon song cua m o t may t h u t h a n h g o m m o t cuon cam thuan CO tU cam k h o n g d o i va m o t t u dien c6 t h e t h a y d o i d i e n dung K h i t u dien c6 dien dung Ci, mach t h u dMc song d i e n tCr c6 huldc song 100 m ; k h i t u d i e n c6 dien dung C2, mach t h u diTcfc song d i e n tii CO hiidc song k m T i so —^ l a : c, A 10 C 100 B 1000 D , Giai Ta c6: ^1000^' c, c, 100 = 100 Vdy chgn dap an C Cdu 47: B i e t k h o i \uang cua h a t n h a n " ^ U l a 234,99 u, cua p r o t o n l a 1,0073 u va cua ncftron l a 1,0087 u N a n g lifong l i e n k e t r i e n g cua h a t nhan " ^ U l a : A 8,71 MeV/nuclon B 7,63 MeV/nuclon C 6,73 MeV/nuclon D 7,95 MeV/nuclon Giai Ta c6: W = Z.m„ + N.m„ - m ^ !^ = 7^63 MeV/nuclon Vdy chgn dap an B Cdu 48: M o t lac dcfn c6 chieu dai day treo m dao dong dieu hoa vdri bien dc goc ^ rad t a i nofi c6 gia toe t r o n g triTcfng g = lOm/s^ L a y 71" = 10 T h d i gian ngan n h a t de iSc d i tii v i t r i can b a n g den v i tri CO l i goc 40 r a d 1^: A 3s B 3V2S C.ls D.,is Q\&\i tig't thi T S D H , C D Mon V$t If 147 Giai Tac6:Acp=-=>At= — = - - = - s to 3Vg Vay chgn dap an C Cdu 49: O m a t chat l o n g c6 h a i nguon song A , B each 20 cm, dao dong theo phifcfng t h a n g dufng vdri phuorng t r i n h la U A = U B = acosSO 7it (t t i n h bang s) Toe t r u y e n song t r e n m a t chat long l a 1,5 m/s T r e n doan t h a n g A B , so d i e m c6 b i e n dao dong cifc d a i va so diem dufng y e n I a n \\sat l a : A va B va C va D va 10 Giai T a c o : X = v T = v — = — = 6cm CO 507t So d i e m c6 b i e n dao dong AB^ AB