II PHAN R I E N G ( c a u ) Thi sinh chi dUt^c lam mgt hai phan rieng (phan A ho0c phanB) A Theo chiTdng trinh C h u a n (10 cau, titcau 41 den cau 50) Cdu 41: M o t v a t nho c6 k h o i lUgfng 500 g dao dong dieu hoa difdri tac dung cua m o t life keo ve c6 bieu thufc F = -0,8cos 4t (N) Dao dong cua v a t CO b i e n l a A cm B 12 cm C cm D 10 cm GISI Clign dap an D Cdu 42: Theo m i u nguyen tijf.Bo, nguyen tuf h i d r o , k h i electron chuyen tii quy dao P ve quy dao K t h i nguyen tuf p h a t r a photon ufng v d i bufc xa c6 t a n so' f i K h i electron chuyen tClf quy dao P ve quy dao L t h i nguyen tijf p h a t r a p h o t o n ufng vdri buTc xa c6 t a n so £2 Neu electron chuyen tCr quy dao L ve quy dao K t h i nguyen tuf p h a t r a photon ufng vdi bufc xa c6 t a n so A £3 = f i - £2 B £3 = £1 + £2 C f = V f ^ • D £ = - ^ I,+12 Giai T a c6: = h£ => e LK = E L - E K => h£LK = E L - Ep + Ep - E K = h£i - h£2 £3 = £1 - £2 Vay chgn dap an A Cdu 43: M o t a n h sang dtfn s&c mau cam c6 t a n so £ difcfc truyen tif chan k h o n g vao m o t chat l o n g c6 chiet suat la 1,5 doi v6i a n h sang T r o n g chat l o n g t r e n , a n h sang c6 D mau t i m va t a n so 1,5£ C mau cam va t a n so £ B mau cam va t a n so 1,5£ A m a u t i m va t a n so £ Giai Chgn dap an C Cdu 44: M o t h a t n h a n X, ban dau dufng y e n , phong xa a va bien t h a n h h a t n h a n Y B i e t h a t n h a n X c6 so k h o i l a A, h a t if p h a t r a too 68 Giai Chi tid't de thi TS DH, CD Mon Vat li V Lay kho'i liig'ng cua h a t n h a n bang so k h o i cua no t i n h theo dcfn vi u Toe cua h a t n h a n Y bang A 4v 2v B A +4 C A-4 4v D A-4 2v A +4 Giai Ap dung d i n h luat bao t o a n dong liTofng ( A - ) V Suy r a : V = 4v „ =i> Do \6n V = A-4 + 4v = 4v A-4 Vay chgn dap an C Cdu 45: M o t m a c h dao dong gom m o t cucn cam t h u a n c6 t i f cam xac d i n h va mot t u dien la tu xoay, c6 dien dung thay doi diTo'c theo quy luat h a m so bac n h a t cua goc xoay a cua b a n l i n h dong K h i a = 0°, t a n so dao dong r i e n g cua mach la M H z K h i a = 120°, t a n so dao dong r i e n g cua mach la I M H z De mach c6 t a n so dao dong rieng bSng 1,5 M H z t h i a bang A 30° B 45° C 60° D.90° Giai Ta c6: C; = tti.K + Co; C = vdi A = 47r=Lf^ Co = f- 47t"L C i = 120.K + Co -r-; Suy r a : 120K = C i - Co = A j A " 120 K f- f- , A J Suy r a : - - = 1,35.10'^ C2 - Co = a K = A fk Suy r a : a = — f- f' 1_ 1_ f- = 45° Vdy chgn dap an B • Cdu 46: M o t v a t dao dong t a t dan c6 cac dai Itfofng nao sau day giam Hen tuc theo thcfi gian? A B i e n va toe B L i va toe C B i e n va gia toe D B i e n va ccr n a n g Giai Chgn idp an D Giai Chi tiet de thi T S DH, C O Mon Vat If 169 - Cdu 47: M o t d o n g cof d i e n x o a y c h i e u b o a t d o n g b i n h thiXdng v6i d i e n a p h i e u d u n g 2 V , c J d n g d o n g d i e n h i e u d u n g 0,5 A v a be so c o n g s u a t cua d o n g ccf l a 0,8 B i e t r k n g c o n g s u a t h a o p h i cua d o n g ccf l a 1 W H i e u s u a t cua d o n g cor ( t i so giOfa c o n g s u a t hufu i c h v a c o n g suat tieu t h u t o a n pban) la A 80% B 90% C , % D 87,5 % Giai C o n g s u a t t i e u t h u t o a n p h a n P = U.I.cosq) = 8 W Suy r a c o n g s u a t hOfu i c h P h = P - Php = 8 - 1 = 7 W P H i e u s u a t c u a d o n g ctf: H = P„p Vdy chon Cdu CO b L f d c dap an 77 = — = 87,5% 88 D 48: 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 v d i a n h s a n g dOn sac s o n g X, k h o a n g e a c h g i a a h a i k h e h e p l a a, k h o a n g e a c h t i ^ m a t p h a n g chufa h a i k h e h e p d e n m a n q u a n s a t l a m T r e n m a n q u a n s a t , t a i d i e m M e a c h v a n s a n g t r u n g t a m m m , c6 v a n s a n g bac K h i t h a y d o i k h o a n g e a c h giufa h a i k h e h e p m o t d o a n b k n g , m m cho v i t r i v a n s a n g t r u n g t a m k h o n g t h a y d c i t h i t a i M c6 v a n s a n g bac G i a t r i cua X b a n g A 0,60 B 0,50 C 0,45 ^im D 0,55 [im Giai m ' • ^ ^ i, a,+0,2 T a co: i j = — = 1,2 m m ; 12 = — = m m ; — = — 6 a, an dap Vdy chgn 1mm; - Suy r a : a i Cdu A 49: D a t d i e n a p x o a y c h i e u u = Uocoscot (UQ k h o n g d o i , co t h a y d o i difac) v a o h a i d a u d o a n m a c h co R, L , C mAc n o i t i e p K h i co = coi t h i c a m k h a n g v a d u n g k h a n g cua d o a n m a c h I a n liTcft l a Z I L v a Z i c Khi CO t h i t r o n g d o a n m a c h x a y r a h i e n ttfgfng c o n g hiforng H e CO = thufc d u n g l a Z CO, - CO, — ^ D CO, =co, C CO, = 0 - , — ^ Z B CO, = A 170 • (Oj , V GiSichitiStd^thiTSBH, CDM6nV*tH ... + Co; C = vdi A = 47r=Lf^ Co = f- 47t"L C i = 120 .K + Co -r-; Suy r a : 120 K = C i - Co = A j A " 120 K f- f- , A J Suy r a : - - = 1,35.10'^ C2 - Co = a K = A fk Suy r a : a = — f- f' 1_ 1_... Chgn idp an D Giai Chi tiet de thi T S DH, C O Mon Vat If 169 - Cdu 47: M o t d o n g cof d i e n x o a y c h i e u b o a t d o n g b i n h thiXdng v6i d i e n a p h i e u d u n g 2 V , c J d n g... i cua X b a n g A 0,60 B 0,50 C 0,45 ^im D 0,55 [im Giai m ' • ^ ^ i, a,+0 ,2 T a co: i j = — = 1 ,2 m m ; 12 = — = m m ; — = — 6 a, an dap Vdy chgn 1mm; - Suy r a : a i Cdu A 49: D a t d