Phương pháp giải nhanh trắc nghiệm vật lý 12

Phương pháp giải nhanh trắc nghiệm vật lý 12

Phng pháp, th thỀt gii nhẬnh ẮáẮ ắng trẮ nghim ềt lý 12   Trang 1   oOo SÁNG KIN - KINH NGHIM TÊN  TÀI: PHNG PHÁP, TH THẠT GII NHANH CÁC DNG TRC NGHIM ạT LÝ 12 NgỀyn Trn Cng Trng THPT ẮhỀyên Lê QỀý ôn Quy Nhn, tháng 5/2010 www.VNMATH.com Phng pháp, th thỀt gii nhẬnh ẮáẮ ắng trẮ nghim ềt lý 12   Trang 2 TÊN  TÀI: PHNG PHÁP, TH THẠT GII NHANH CÁC DNG TRC NGHIM ạT LÝ 12 A. M Ạ 1. LỦ do chn đ tài:              không quá 1,5 phút  và các công   trình. 2. Nhim v ca đ tài ậ Gii hn đ tài. Ậ. Nhim ề ẮẬ ơ ếài:       ậ. Gii hn ơ ếài:    +   Ắ. Hng phốế ếrin ơ ếài:      3. Phng pháp tin hành.    giáo khoa. 4. C s và thi gian tin hành nghiên cu đ tài.    www.VNMATH.com Phng pháp, th thỀt gii nhẬnh ẮáẮ ắng trẮ nghim ềt lý 12   Trang 3 MC LC Trang A. M U  01    01 nh. 01  01 B. NI DUNG PHN MT: NG TRÒN LNG GIÁC  02  02  03  06  08  09 PHN HAI: TNG HP DAO NG IẠ HÒA  10  10  11  12  14  14 PHN BA: GIAO THOA SÓNG C  15  15  16  19  21  21  22 C. KT LUN  23  23  23 TÀI LIU THAM KHO  .  -  .   . T  www.VNMATH.com Phng pháp, th thỀt gii nhẬnh ẮáẮ ắng trẮ nghim ềt lý 12   Trang 4  PHN MT NG TRÒN LNG GIÁC 1. Mô t tình trng s vic hin ti :                  x = Acos(t +                  =Acos(t+ 1  2   * Nhn ếhy mế s nhẮ ơim ẮẬ phng phốp này khi làm ếrẮ nghim:  t + ) m - Asin(t + i a = - 2 Acos(t + ). Lúc                 tròn  (v),    /2          l                       2. Mô t ni dung gii pháp mi : Ậ. C s lỜ ếhỀyế :   + (t +  x ) + -  Asin(t +  x ) -  2 Acos(t +  x ) ậ. Gii phốp mi:    os(t + x  ) là hàm cosin  max = A O a x v I II IV III x  V  a  1 2 3 4 www.VNMATH.com Phng pháp, th thỀt gii nhẬnh ẮáẮ ắng trẮ nghim ềt lý 12   Trang 5   = - Asin(t +  x                  V max = A  Acos(t +  V  /2 vx       = -  2 Acos(t +  x ) = - 2    max = 2  A  2 Acos(t +  a  /2 a x v              sau : + Bn ơim ơẮ ậiế: -  ( x max = A ; v = 0 ; a = - 2  A)  -  ( x = 0 ; v = - A  ; a = 0 )  -  ( x = -A ; v = 0 ; a max = 2  A )  -  ( x = 0 ; V max = A  ; a = 0)       + Bn ềủng ơẮ ậiế: Vùng 1: x>0 ; v<0 , a<0 u (-  Vùng 2: x<0 ; v<0 , a>0      -          Vùng 3: x<0 ; v>0 , a>0    Vùng 4: x>0 ; v>0 , a<0       + Mi qỀẬn h ề phẬ ẮẬ li ơ (x), ền ếẮ (ề), giẬ ếẮ (Ậ):   /2 vx     và /2 a x v           /2   /2   góc /2   a x v O I II IV III 1 2 3 4 www.VNMATH.com Phng pháp, th thỀt gii nhẬnh ẮáẮ ắng trẮ nghim ềt lý 12   Trang 6 3. Chng minh tính kh thi ca gii pháp mi:                   Câu 01    A. v = 0cm/s. B. v = 75,4cm/s. C. v = - 75,4cm/s. D. v = 6cm/s. Gii:         t  =2  .7,5 = 15        Câu 02.          t + /2    A. a = 0cm/s 2 B. a = 946,5cm/s 2 . C. a = - 946,5cm/s 2 D. a = - 946,5cm/s. Gii:     góc t  = 4  .5 = 20   - 2 A  = - 947,5cm/s 2  Câu 03.              v=10  cos(2  t + /2   A. x = 1,5cm. B. x = - 5cm. C. x= + 5cm. D. x = 0cm. Gii:  quay 1 góc t  =2  .1,5 = 3   -  Câu 04:       2cos(0,5t                A. 8/3s B. 2/3s C. 2s D. 4/3s Gii:                = 0,5  . t =      Câu 05.             3 cm theo    A. v = 4cos(3  t - /3  )cm./s B. v = 4  cos(  t + /3  )cm./s C. v = 4cos(3  t + /6  )cm/s. O a x v I II IV III Hình 1 O a x v I II IV III V VI  Hình 2 O a x v I II IV III Hình 3 V /3  www.VNMATH.com Phng pháp, th thỀt gii nhẬnh ẮáẮ ắng trẮ nghim ềt lý 12   Trang 7 D. v = 4  cos(  t - /6  )cm/s Gii:  là + /3  ,   A = 4    => hàm v = 4  cos(  t + /3  )cm./s ,  Câu 06: cos(0,5t-/6) cm/s.   A. 6s B. 2s C. 4/3s D. 14/3s Gii:              V max =A  =2      Câu 07:              t (cm/s 2  10 m/s 2   A. 5N B. 1 N C. 5,5N D.  Gii:          => F = k  l 0 = mg = 5 N Câu 08:   = 10 m/s 2                 cos(5t - 2  A. 1/30s B. 11/30s C. 1/25s D. 1/10s Gii:  giãn 0 2 4( ) mg g l cm k                 -      => góc quay 5  .t = /2   Câu 09:     5 /6 0,5 t                         3       O a x v I II IV III V VI /3  Hình 4 a x v I II IV III Hình 6 VI V 5 /6  O a x v I II IV III Hình 5 VI V /2  www.VNMATH.com Phng pháp, th thỀt gii nhẬnh ẮáẮ ắng trẮ nghim ềt lý 12   Trang 8 A. 6(s) B. 3(s) C. 2/3(s) D. 4/3(s) Gii:                0    x=4cos( 0,5 5 /6t   )  t  = 0,5  .t =  ( vì   Câu 10 :              v=24  cos(4t+           1     2 = 37/12 (s) là A. 141cm B. 96cm C.234cm D. 117cm Gii:                 t 1 =      1 2 4 3           21 29 12 t t t    s quay  29 2 49 12 3             => s =18A+0,5A+1A=19,5x6 =117 (cm),  4. Mt s vn đ liên quan và vn dng: Ậ. ạn ơ liên qỀẬn:    S tng t giẬ ắẬo ơng Ắ ềà ắẬo ơng ơin t i lng Ắ i lng ơin t DẬo ơng Ắ DẬo ơng ơin t x q  2 x = 0  2 q = 0 v i k m   1 LC   m L x = Acos(t + ) q= q 0 cos(t + ) k 1 C -Asin(t+ ) -q 0 sin(t+) F u 2 2 2 () v Ax   2 2 2 0 () i qq   µ R F = -kx = -m 2 x 2 q u L q C   W  W t (W L ) W  = 1 2 mv 2 W t = 1 2 Li 2 W t W  (W C ) W t = 1 2 kx 2 W  = 2 2 q C   C )   L ) O a x v I II IV III Hình 7 VI V /6  www.VNMATH.com Phng pháp, th thỀt gii nhẬnh ẮáẮ ắng trẮ nghim ềt lý 12   Trang 9       + Bn ơim ơẮ ậiế: -  max = Q 0 ; i = 0 ; u L = - 0 Q C = - L 2  Q 0 )           - = - 0 Q  ; u L = 0 )           - -Q 0 ; i = 0 ; u L max = 0 Q C = L 2  Q 0 )           -  IV: ( q = 0 ; i max = 0 Q  ; u L = 0)                    + Bn ềủng ơẮ ậiế: Vùng 1: q>0, i<0, u L <0  Vùng 2: q<0, i<0, u L >0  Vùng 3: q<0, i>0, u L >0  Vùng 4: q>0, i>0, u L <0  +Mi qỀẬn h ề phẬ ẮẬ ơin ếỜẮh (q), Ắng ơ ắỢng ơin ếẮ ếhi (i), ơin áp ếrên hẬi ơỀ ẮỀn ắồy (Ề L ):   L ): /2 iq     và /2 L u q i          .    C  /2   L  góc /2  .  L   /2   ậ. Phn ắành Ắho hẮ sinh ền ắng, ếỜnh ếoốn ếr li : Câu 01            -4 s   A. 4,0.10 -4 s. B. 0,5.10 -4 s . C. 1,0.10 -4 s. D. 2,0.10 -4 s. . Câu 02.         A. 5  .10 -6 s. B. 2,5  .10 -6 s. C . 10  .10 -6 s. D. 10 -6 s. u L O q i I II IV III q  i  L u  1 2 3 4 www.VNMATH.com Phng pháp, th thỀt gii nhẬnh ẮáẮ ắng trẮ nghim ềt lý 12   Trang 10  Câu 03.   0 .  A. t = 8.10 -5 (s). B. t = 4.10 -5 (s). C. t = 2.10 -5 (s). D. t = 10 -5 (s).  Câu 04.   4 t +    A. t = 0,5.10 - 4 (s). B. t = 10 - 4 /3 (s). C. t = 0,67.10 - 4 (s). D. t = 10 - 4 /6 (s).  Câu 05.   W = 0,25.10 -3    A. u = 250 cos (25.10 6 t - /2)(V). B. u = 250 cos(25.10 6 t +)(V). C. u = 250 cos (25.10 6 t)(V). D. u = 220 cos (25.10 6 t)(V).  Câu 06.   0  gian là lúc q = - 3 Q 0  A. q = 10 -4 cos (100t + /2)(C). B. q = 10 -4 cos (100t + /6)(C). C. q = 0,01cos (1000t - /6) (mC). D. q = 0,1cos (1000t + 7/6)(mC)  Câu 07. in10 4 t(V),   F).  A. i = 2.10 -2 cos (10 4 t ) (A) B. i = 2.10 2 sin(10 4 t +  ) (A) C. i = 2cos (10 4 t +  /2) (A) D. i = 0,02cos(10 4 t-  ) (A)  Câu 08.   trình q = Q 0 cos(7000t +   A. 74,8 s B. 14,96  C. 112,22 s D. 186,99s  Câu 09.      A. 3,2mJ. B. 0,256mJ. C. 0,320mJ. D. 0,288mJ  Câu 10.  0 sin(2ft +    tiêu là A. I 0 /2f (C). B. 2I 0 /f (C) C. I 0 /f (C) D. I 0 /4f (C).  5. u đim: giúp c www.VNMATH.com [...]... ( M ) d1 d 2 và 2 570ES thì - Trang 23 www.VNMATH.com 2009: -2009 12L 12T 12Si -2009 9,55 9,61 9,30 8,90 8,83 x 2010: ) (%) Trung bình Kém Khá (0 =>2.0) (2.5=>5.0) (5.5=>6.0) (6.6=>7.5) (8.0=>10) 12L 23 0 0% 0 0% 3 13,04% 2 8,70% 18 78,26% 12T 25 0 0% 0 0% 5 20,00% 3 12, 00% 17 68,00% 12Si 30 0 0% 1 3,33% 7 23,33% 6 20,00% 16 53,34% 12A1 40 1 2,50% 2 5,00% 10 25,00% 9 22,50% 18 45,00% (%) 130 118 Kém... + A 7 C 6 B 8 v f 12 2 D 5 6(cm) d1 d 2 M ( ) M 2k => (d1-d2) = (2k ) 2 6 2 6k 3 mà AB < d1-d2 < AB nên ta có Câu 06: 1 = acos(40 t), u2 = bcos(40 t + sao B 6 A 7 v f 40 20 C 5 2(cm) D 4 d1 d 2 ( M ) 2 Trang 19 www.VNMATH.com mà AB/3 => (d1-d2) = (2k 2k M d1-d2 AB/3 nên ta có -2 ) 2 2 2k 1 k Câu 07: 1 A 10 C 12 B 11 v f 30 15 D 13 2(cm) d1 d 2 => (d1-d2) = (2k 1) / 2) 2 2 ( d1- d2 12 M ) 2 (2k 1) M... www.VNMATH.com C x 5cos( t / 2) cm Câu 10: D x 5cos( t / 4) cm 4 , x1= 3 cos 2 t (cm), x2 = 3 3 cos( 2 t x3=6cos( 2 t 4 ) (cm) , x4= 6cos( 2 t 3 2 )(cm), 2 )(cm) 3 4 )(cm) 3 4 ) (cm) C x = 12cos( 2 t 3 A x=6cos( 2 t B x = 6cos( 2 t D x= 12cos( t 2 )(cm) 3 3 )(cm) - phút : Khi tính còn tính theo hàm tan iáo viên có fx 570ES MODE 1 Trang 16 www.VNMATH.com 1, 1, 1, l u1 u1M Acos(2 ft 2 d1 u2 ) và u2 M u S2 cách nhau... 2Cos(100 t) V C u AC 2cos 100 t D 10 (cm/s) , = cos100 t (V) BC = 3cos(100 t- AC B u AC 2cos 100 t D u AC 2cos 100 t /3 V /3 V /3 V Câu 07: / 3 cm , x1 2 3cos 2 t x2 4cos 2 t / 6 cm và x3 8sin 2 t cm A 12 C / 3 (rad) / 6 (rad) B D / 6 (rad) - / 6 (rad) Câu 08: i1 5 2cos(100 t ) (A); i2 8 3cos(100 t 2 / 3) (A) và i 3 5cos(100 t 2 / 3) 3 A i 6,97cos(100 t 2,05) (A) C i 6,97cos(100 t 1,09) (A) Câu 09: x4...www.VNMATH.com t ) nào /2 12 1 2 /2 C ) Trang 11 www.VNMATH.com : x1= A1cos( t+ 1) và x2=A2cos( t + t+ ) A2 A2 A2 2 AAcos( 1 2 1 2 A sin 1 A sin 2 1 2 Acos 1 A cos 2 1 2 và tan 1, 2 1 tan 2 A Asin Acos 1 2 x2 cùng pha) 1, x2 =... t + 1 2 ) 2 x = Acos( t + ) Chi A x A 2 Ax Acos Acos 1 2 Ay và tan 1 Acos 2 Ay 2 và Ay [ Ax Asin Min, A sin 1 A sin 2 1 2 Max] giáo viên hay 2 =1 thì = /4 3 /4 x Acos t A * = Aej ( t ) vì các Trang 12 www.VNMATH.com * = Ae j trong máy tính CASIO fx- 570ES A -1800< oà 1800 hay < 570ES ) SHIFT MODE A SHIFT MODE 32 31 Mode CMPLX Ta MODE 2 D thì R SHIFT MODE 3 SHIFT MODE 4 SHIFT x 6cos t /3 6 - 6 SHIFT... d1-d2 AB/3 nên ta có -2 ) 2 2 2k 1 k Câu 07: 1 A 10 C 12 B 11 v f 30 15 D 13 2(cm) d1 d 2 => (d1-d2) = (2k 1) / 2) 2 2 ( d1- d2 12 M ) 2 (2k 1) M ta có -6,25 = acos(30 t), u2 = bcos(30 t + /2) 2k 0,5 mà 12 k Câu 08: 1 A 8 = acos(8 t), u2 = bcos(8 B 9 v f C 10 D 11 4 1(cm) 4 C D 10cm d1 d 2 ( ) M 6cm 2 8cm M A (2k 1) => (d1-d2) = (2k 1) mà 4 d1-d2 Câu 09: 0) 1 2 B k 0,5 4 nên ta có - 4,5 k là u1 = acos(8... cm và x3=3cos(20t+2 /3) (cm) B 5,82cm; -1,15 rad D.8,80cm; 1,15 rad /2 3 2 /3 H 4.82 1,15 Trang 13 www.VNMATH.com Câu 3: x=5 2 cos( t + 5 x 1 =A1 cos( t + 1 ) x 2 =5cos( t+ A 1 = 2 /3 B 1 = /2 5 2 5 /12 5 C /6 = 1 5 /4 D 1 = /3 A 2 /3 Câu 4: 1 = 2 3 cos(2 t + /3) cm, x2 = 4cos(2 t + /6) cm và t- A 8cm và - /2 6 * /6 B 6cm và /3 2 3 /3 4 C 8cm và /6 /6 8 D 8cm và /2 /2 : a+bi a + bi A - A a + bi . www.VNMATH.com Phng pháp, th thỀt gii nhẬnh ẮáẮ ắng trẮ nghim ềt lý 12   Trang 2 TÊN  TÀI: PHNG PHÁP, TH THẠT GII NHANH CÁC DNG TRC. oOo SÁNG KIN - KINH NGHIM TÊN  TÀI: PHNG PHÁP, TH THẠT GII NHANH CÁC DNG TRC NGHIM ạT LÝ 12 NgỀyn Trn Cng. www.VNMATH.com Phng pháp, th thỀt gii nhẬnh ẮáẮ ắng trẮ nghim ềt lý 12   Trang 6 3. Chng minh tính kh thi ca gii pháp mi:  