Giai U = U.27if, neu f cang Idrn thi I cang \6n Ta c6: I = — Vay chgn dap an B Cdu 37: Vat dao dong tat dan c6 A ccf nang luon giam dan theo th6i gian B the n^ng luon giam dan theo thdri gian C li luon giam dan theo thdi gian D pha dao dong luon giam dan theo thcfi gian Giki Vat dao dong tkt dan c6 ccf nSng luon giam dan theo th&i gian Vay chon dap an A Cdu 38: Trong may phat dien xoay chieu ba pha dang hoat dong, suat dien dong xoay chieu xuat hien m6i cupn day cua stato c6 gia tri cLfc dai la E Q Khi suat dien dong tufc thofi mot cuon day bkng thi suat dien dong tufc thcfi m6i cuon day lai c6 16n bang va bkng: A D Giai Ta c6: e i = Eocoscot; Gia suf e i = ez = EQCOS cot = ±^ V cot- j 2n e = E Q C O S (Ot + - Thay vao bieu thuTc 82 va ea ta difcfc e2 = 63 = Vay chgn dap an A Cdu 39: Khi n6i ve dao dong dieu hoa, phat bieu n^o sail day diing? A Dao dong cua iSc 16 xo luon la dao dong dieu hoa B Ccf nSng cua vat dao dong dieu hoa khong phu thuoc bien dao dong C Hgrp life tac dung len vat dao dong dieu hoa luon hifdrng ve vi tri can bkng ^ D Dao dong cua lac dcfn luon la dao dong dieu hoa GiSi Chi l\6i de thi TS DH, CD M6n V$t U 144 G\k\ Chi Cdu CO dap an C dung, cdc dap an lai deu sai 40: D u n g h a t a b a n p h a h a t n h a n nitcf d a n g dufng y e n t h i t h u dxigc m o t h a t p r o t o n v a h a t n h a n o x i t h e o p h a n ufng: ^a + ' ^ N ^ ' g O + j p Biet k h o i hicfng cac h a t t r o n g p h a n Ofng t r e n l a : m^, = 4,0015 u ; niN = 13,9992u; mo = , 9 u ; nip = l , 0 u N e u bo q u a d o n g n a n g cua cac h a t t h i d o n g n a n g t o i t h i e u cua h a t a A 1,503 MeV sinh la: B 29,069 M e V C 1,211 MeV D 3,007 M e V Giai A p d u n g d i n h l u a t b a o t o a n n a n g lifc^ng, t a c6: + moc' = m c ' ^ Vay Cdu chgn 41: dap an W,„ = m c ' - nioc' = , IMeV C C h o d o n g d i e n x o a y c h i e u c6 t a n so 50 H z c h a y q u a m o t d o a n m a c h K h o a n g t h d i g i a n giOfa h a i I a n l i e n t i e p c i f d n g d o n g d i e n n a y bang la: A — s 100 B — s 200 C — s 50 D —s 25 Giai K h o a n g t h o i g i a n giufa h a i I a n l i e n t i e p ciTcfng d o n g d i e n b k n g l a : T \ ' \ — =-f = Vay chgn s 100 dap an A Cdu 42: T h e o m a u n g u y e n tuf B o , t r a n g t h a i dCfng cua n g u y e n tijf A CO t h e l a t r a n g t h a i ca b a n h o a c t r a n g t h a i k i c h t h i c h B chi la t r a n g t h a i k i c h t h i c h C l a t r a n g t h a i m a cac e l e c t r o n t r o n g n g u y e n tuf n g i t o g c h u y e n d o n g D c h i l a t r a n g t h a i ccf b a n Giai T h e o m a u n g u y e n tuf B o , t r a n g t h a i dCifng cua n g u y e n tuf c6 t h e la t r a n g t h a i ccf b a n hohc t r a n g t h a i k i c h t h i c h Vay Cdu 43: chgn dap an A T r o n g t h i n g h i e m Y - a n g ve g i a o t h o a a n h s a n g , k h o a n g e a c h giila h a i k h e l a m m , k h o a n g e a c h t t f m a t p h a n g chufa h a i k h e den m a n q u a n s a t l a m N g u o n p h a t a n h s a n g g o m cac bufc x a dofn s&c Giai chi ti^t (36 thi TS DH, CD M6n V a t II c6 45 blidc song khoang tCf 0,40 |am den 0,76 j i m Tren man, tai diem each van trung tarn 3,3 mm c6 bao nhieu bufc xa cho van toi? A bufc xa B bufc xa C bufc xa D hdcxa Giai ID Cac bufc xa cho van toi c6: x = (k + , ) — => A, = Ta lai C O : 0,4^m < X < 0, ;6^m 0,4|im < a.x (k + 0,5)D a.x < 0,76nm (k + 0,5)D ^ 3,9 < k < 7,75 Vay k = 4; 5; 6; hay c6 bufc xa Vay chon dap an B Cdu 44: Do lech pha cua hai dao dong dieu hoa cung phiicfng, cung tan so va ngiTofc pha la: A (2k + l ) ^ ( v d r i k = 0, ±1, ± , ) B k i ( v d i k = 0, ±1, ±2, ) C (2k + l ) r ( v d i k = 0, ±1, ±2, ) D 2k7r ( v d i k = 0, ±1, ± , ) Giai \ Do lech pha cua hai dao dong dieu hoa cung phLforng, cung tan so va ngLfgfc pha la (2k + l)7r (vdri k = 0, ±1, ±2, ) Vay chgn dap an C Can 45: K h i truyen dien nang c6 cong suat P tCf nofi phat dien xoay chieu den ncfi tieu thu t h i cong suat hao phi tren dirofng day la AP De AP cho cong suat hao phi tren du'dng day chi la — (vo'i n > 1), d ncfi n phat dien ngiiM ta suf dung mot may bien ap (li tLforng) c6 ti so giufa so vong day cua cuon scf cap 1va so vong day cua cuon thuf cap la: A Vn D C n B n GiSi Taco: AP, = A R U = 146 Glai Chi tiet de thi T S D H , CD M n Vat If f- ... phiicfng, cung tan so va ngiTofc pha la: A (2k + l ) ^ ( v d r i k = 0, ±1, ± , ) B k i ( v d i k = 0, ±1, ? ?2, ) C (2k + l ) r ( v d i k = 0, ±1, ? ?2, ) D 2k7r ( v d i k = 0, ±1, ± , ) Giai... niN = 13,9992u; mo = , 9 u ; nip = l , 0 u N e u bo q u a d o n g n a n g cua cac h a t t h i d o n g n a n g t o i t h i e u cua h a t a A 1,503 MeV sinh la: B 29 ,069 M e V C 1 ,21 1 MeV D ... 100 B — s 20 0 C — s 50 D —s 25 Giai K h o a n g t h o i g i a n giufa h a i I a n l i e n t i e p ciTcfng d o n g d i e n b k n g l a : T ' — =-f = Vay chgn s 100 dap an A Cdu 42: T h e o