Hướng dẫn giải chi tiết đề thi tuyển sinh đại học, cao đẳng môn vật lí phần 2 tờ số (26)

Ta : x, = C O X , => k,.!, = k , i , k k A, = k , A =>—!- = - i = _ " " k, >i, Co v a n s a n g Xi v a v a n s a n g A.2 Vdy chon dap Cdu T o n g hgrp h a t n h a n h e l i 19: an [ H + j L i - ^ jHe + X A M6i phan jHe ufng t r e n tOf p h a n i J n g h a t toa nang liTong 17,3 nhan MeV N a n g liTdng t o a r a k h i t o n g hgfp dUdc 0,5 m o l h e h l a A 1,3.10'" M e V B 2,6.lO'" MeV C , ' " M e V D 2,4.10'" M e V Giai H a t n h a n X c u n g l a h a t H e n e n so p h a n ufng b a n g m o t nijfa so h a t T a c o : E = , ^ = 2,6.10^' Vdy chgn Cdu 20: dap an MeV B M o t s o n g a m v a m o t s o n g a n h s a n g t r u y e n tii k h o n g k h i vao nifdrc t h i bi/dfc s o n g A cua s o n g a m t a n g bUo'c s o n g cua s o n g a n h s a n g g i a m B cua s o n g a m g i a m btTo'c s o n g ciia s o n g a n h s a n g t a n g C cua s o n g a m v a s o n g a n h s a n g deu g i a m D cua s o n g a m v a s o n g a n h s a n g d e u t a n g Giai V a n toe t r u y e n a m t r o n g ni/o'c t a n g , v a n toe t r u y e n s o n g a n h s a n g t r o n g nu'd'c g i a m m a t a n so k h o n g d o i Vdy chon Cdu 21: dap an A T r o n g gior thiTc h a n h , m o t hoc sinh mac doan mach AB gom d i e n t r d t h u a n Q, t u d i e n c6 d i e n d u n g C t h a y d o i dtrgfc v a c u o n day C O t U c a m L n o i t i e p n h a u t h e o d u n g thuf i\i t r e n G o i M l a d i e m n o i giufa d i e n t r t f t h u a n v a t u d i e n D a t v a o h a i d a u d o a n m a c h AB m o t d i e n a p x o a y c h i e u c6 g i a t r i h i e u d u n g 0 V v a t a n so 50 H z K h i dieu c h i n h d i e n d u n g cua t u d i e n d e n g i a t r i Cm t h i d i e n a p h i e u d u n g giufa h a i d a u d o a n m a c h M B d a t g i a t r i CLTC t i e u b a n g 75 V D i e n t r d t h u a n ciia c u o n d a y l a A 24 D C 30 Q B 16 Q D Q Giai D i e u c h i n h C de T a c6: U M B Vdy chon ULCmax- = U , = 75V dap an K h i x a y r a c o n g h i i d n g U R = 125V , R = Q => r = 24Q A Giai Chi t I e t d S thi T S D H , CD M o n vat li , 159 Cdu 22: K h i n o i ve song dien tCf, p h a t bieu nao sau day la s a i ? A Song d i e n tCr m a n g nang lifc/ng B Song d i e n tCf t u a n theo cac quy luat giao thoa, n h i e u x a C Song d i e n tii l a song ngang D Song d i e n tCr k h o n g t r u y e n di/Oc t r o n g chan k h o n g Giai Chgn dap an D Cdu 23: K h i n o i ve sii t r u y e n song co t r o n g m o t m o i triio'ng, phat bieu nao sau day dung? A Nhurng p h a n tuf cua m o i trtfdng each m o t so nguyen I a n biTdtc song t h i dao dong cung pha B H a i p h a n tuf ciia m o i trtfo'ng each m o t p h a n tu hitdc song t h i dao dong lech p h a 90° C NhuTng p h a n tuf cua m o i trifc/ng t r e n cung m o t hiidfng truyen song va each m o t so nguyen I a n hiXdc song t h i dao dong cung pha D H a i p h a n tuf ciia m o i t r i i d n g each m o t nufa hxx6c song t h i dao dong ngiitfc pha Giai Chgn dap an C Cdu 24: D i e n n a n g tCr m o t t r a m p h a t d i e n dtroc di/a den m o t khu t a i d i n h cir b k n g difofng day t r u y e n t a i m o t pha Cho biet, neu dien ap t a i dau t r u y e n d i t a n g t\i U l e n U t h i so ho d a n diJOc t r a m cung cap du dien n a n g t a n g tii 120 l e n 144 Cho rang c h i t i n h den hao p h i t r e n di/6'ng day, cong suat tieu t h u dien ciia cac ho d a n deu nhxi nhau, cong suat cua t^am p h a t k h o n g doi va he so cong suat t r o n g cac triio'ng hop deu bang N e u dien ap t r u y e n d i l a U t h i t r a m p h a t huy cung cap du d i e n n a n g cho D 192 ho d a n C 504 ho dan B 150 ho dan A 168 ho dan Giai • B a n dau: P N = 120Po + Php 1 K h i U t a n g I a n t h i Php g i a m I a n : P N = 144Po + - Php Suyra:P„^=32P„ K h i U t a n g I a n t h i Php g i a m 16 I a n : P,,,, = 2?^ Ta c6: 32Po - 2Po = 30Po (cung cap t h e m di/Oc 30 ho) Vqy chgn dap an B 160 Giai C h i trSt de t h i T S B H , C D M n Vat l( Cdu 25: Tren mot sgri day cang ngang vdi hai dau co dinh dang c6 s o n g dCtog Khong xet cAc diem bung hoac nut, quan sat thay nhuTng diem c6 cung bien va of gan nhat t h i deu each deu 15cm B L T O C song tren day c6 gia t r : bang A 30 cm B 60 cm C, 90 cm D 45 cm GiSi Cac diem c6 cung bien deu each deu t h i each mot khoang — = 15cm Suy ra: X = 60 cm Vdy chon dap an B Cdu 26: TOf mot tram phat dien xoay chieu mot pha dat t a i v i t r i M, dien nang di/gfc truyefi tai den ncfi tieu thu N , each M 180 km Biet dirdng day c6 dien t r d tong cong 80 Q (coi day tai dien la dong chat, co dien trd t i le thuan vdi chieu dai cua day) Do sir co, difdng day bi ro dien tai diem Q (hai day tai dien bi noi tat bdi mot vat co dien trof co gia t r i xac dinh R) De xac dinh v i t r i Q, trtrdfe tien ngUofi ta ngat diiofng day l ^ o i may phat va t a i tieu thu, sau dung nguon dien khong doi 12V, dien trof khong dang ke, noi vao hai dau cua hai day t a i dien t a i M Khi hai dau day t a i N de hof t h i ci/dng dong dien qua nguon la 0,40 A, hai dau day tai N difofc noi t a t bdi mot doan day co dien trd khong dang ke t h i ciTofng dong dien qua nguon la 0,42 A Khoang each MQ la A 135 km B 167 km C 45 km.D 90 k m Giai 12 Luc dau (Rd nt R) ta co: Rd + R = — 0,4 Luc sau [Rd nt (R // 80 - Rd)] ta co: R, + (1) Rf80 —R ) K + oU —Kj R Giai (1) va (2) ta c6: Rd = 20; R = 10 =^ 12 -— U, 4z (2) X = — ^ X = 45km 80 180 Vdy chqn dap an C Cdu 27: Dat dien ap u = Uocoscot (V) ( U Q khong doi, co thay doi dirgfc) vao hai dau doan mach gom dien t r d thuan R, cuon cam thuan CO tir cam — H va tu dien mSc noi tiep Khi co = coo t h i CLfcfng 571 dong dien hieu dung qua doan mach dat gia t r i dai I ^ K h i co = coi hoac CO = C t h i cifdng dong dien eiie dai qua doan mach bang C L T C va bang Im Biet coi - C O = 2OO71 rad/s Gia t r i cua R bang A 150 Q B 200 Q Gi4i Chi tiet de thi TS DH, CO M6n vat If C 160 Q D 50 Q 161 ... g i a m 16 I a n : P,,,, = 2? ^ Ta c6: 32Po - 2Po = 30Po (cung cap t h e m di/Oc 30 ho) Vqy chgn dap an B 160 Giai C h i trSt de t h i T S B H , C D M n Vat l( Cdu 25 : Tren mot sgri day cang ngang... + (1) Rf80 —R ) K + oU —Kj R Giai (1) va (2) ta c6: Rd = 20 ; R = 10 =^ 12 -— U, 4z (2) X = — ^ X = 45km 80 180 Vdy chqn dap an C Cdu 27 : Dat dien ap u = Uocoscot (V) ( U Q khong doi, co thay... eiie dai qua doan mach bang C L T C va bang Im Biet coi - C O = 2OO71 rad/s Gia t r i cua R bang A 150 Q B 20 0 Q Gi4i Chi tiet de thi TS DH, CO M6n vat If C 160 Q D 50 Q 161