Tong hop cac dang bai tap vat ly 12

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  • 1. CtnSharing.Net.TcM cl cM cl c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1Ph n1 . PHNG PHP GI I TON V DAO NG I U HA C A CON L C L XO15Ch 1. Lin h gi a l c tc d ng, gin v c ng c a l xo . . . . . . . . . .15 1.Cho bi t l c ko F , c ng k: tm gin l0, tm l . . . . . . . . . . . . . 15 2.C t l xo thnh n ph n b ng nhau ( ho c hai ph n khng b ng nhau): tm c ng c a m i ph n . . . . . . . . . . . . . . . . . . . . . . . . . . . .15Ch 2. Vi t phng trnh dao ng i u ha c a con l c l xo . . . . . . . . . . 15Ch 3. Ch ng minh m t h c h c dao ng i u ha . . . . . . . . . . . . . . . 16 1.Phng php ng l c h c . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 2.Phng php nh lu t b o ton nng l ng . . . . . . . . . . . . . . . . . .16Ch 4. V n d ng nh lu t b o ton c nng tm v n t c . . . . . . . . . . . . 16Ch 5. Tm bi u th c ng nng v th nng theo th i gian . . . . . . . . . . . . 17Ch 6. Tm l c tc d ng c c i v c c ti u c a l xo ln gi treo hay gi . . 17 1.Tr ng h p l xo n m ngang . . . . . . . . . . . . . . . . . . . . . . . . . . 17 2.Tr ng h p l xo treo th ng ng . . . . . . . . . . . . . . . . . . . . . . . 17 3.Ch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17Ch 7. H hai l xo ghp n i ti p: tm c ng kh , t suy ra chu k T . . . . 18Ch 8. H hai l xo ghp song song: tm c ng kh , t suy ra chu k T . . .18Ch 9. H hai l xo ghp xung i: tm c ng kh , t suy ra chu k T . . . 18Ch 10. Con l c lin k t v i rng r c( khng kh i l ng): ch ng minh r ng h dao ng i u ha, t suy ra chu k T . . . . . . . . . . . . . . . . . . . .19 1.Hn bi n i v i l xo b ng dy nh v t qua rng r c . . . . . . . . . . . . . .19 2.Hn bi n i v i rng r c di ng, hn bi n i vo dy v t qua rng r c . . . . 19 3.L xo n i vo tr c rng r c di ng, hn bi n i vo hai l xo nh dy v t qua rng r c . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

2. Ch 11.L c h i ph c gy ra dao ng i u ha khng ph i l l c n h i nh: l c y Acximet, l c ma st, p l c th y t nh, p l c c a ch t kh...: ch ng minh h dao ng i u ha . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 1.F l l c y Acximet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20 2.F l l c ma st . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20 3.p l c th y t nh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21 4.F l l c c a ch t kh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21Ph n2 . PHNG PHP GI I TON V DAO NG I U HA C A CON L C N22Ch 1. Vi t phng trnh dao ng i u ha c a con l c n . . . . . . . . . . .22Ch 2. Xc nh bi n thin nh chu k T khi bi t bi n thin nh gia t c tr ng tr ng g, bi n thin chi u di l . . . . . . . . . . . . . . . . . . .22Ch 3. Xc nh bi n thin nh chu k T khi bi t nhi t bi n thin nh t; khi a ln cao h; xu ng su h so v i m t bi n . . . . . . . . . . .23 1. Khi bi t nhi t bi n thin nh t . . . . . . . . . . . . . . . . . . . . . .23 2. Khi a con l c n ln cao h so v i m t bi n . . . . . . . . . . . . . . .23 3. Khi a con l c n xu ng su h so v i m t bi n . . . . . . . . . . . . .23Ch 4. Con l c n ch u nhi u y u t nh h ng bi n thin c a chu k: tm i u ki n chu k khng i . . . . . . . . . . . . . . . . . . . . . . . . . .24 1.i u ki n chu k khng i . . . . . . . . . . . . . . . . . . . . . . . . .24 2.V d :Con l c n ch u nh h ng b i y u t nhi t v y u t cao . . .24Ch 5. Con l c trong ng h g giy c xem nh l con l c n: tm nhanh hay ch m c a ng h trong m t ngy m . . . . . . . . . . . . . . . . . . .24Ch 6. Con l c n ch u tc d ng thm b i m t ngo i l c F khng i: Xc nh chu k dao ng m i T . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 1.F l l c ht c a nam chm . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 2.F l l c tng tc Coulomb . . . . . . . . . . . . . . . . . . . . . . . . . .25 3.F l l c i n tr ng . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25 4.F l l c y Acsimet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26 5.F l l c n m ngang. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26Ch 7. Con l c n treo vo m t v t ( nh t, thang my...) ang chuy n ng v i gia t c a: xc nh chu k m i T . . . . . . . . . . . . . . . . . . . . . .26 1.Con l c n treo vo tr n c a thang my ( chuy n ng th ng ng ) v i gia t ca . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27 2.Con l c n treo vo tr n c a xe t ang chuy n ng ngang v i gia t c a . 27 3. 3.Con l c n treo vo tr n c a xe t ang chuy n ng trn m t ph ngnghing m t gc : . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28Ch 8. Xc nh ng nng E th nng Et , c nng c a con l c n khi v tr c gc l ch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29Ch 9. Xc nh v n t c di v v l c cng dy T t i v tr h p v i phng th ng ng m t gc . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29 1.V n t c di v t i C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 2.L c cng dy T t i C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29 3.H q a: v n t c v l c cng dy c c i v c c ti u . . . . . . . . . . . . . .30Ch 10. Xc nh bin gc m i khi gia t c tr ng tr ng thay i t g sang g 30Ch 11. Xc nh chu k v bin c a con l c n v ng inh (hay v t c n) khi i qua v tr cn b ng . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 1.Tm chu k T . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30 2.Tm bin m i sau khi v ng inh . . . . . . . . . . . . . . . . . . . . . . 31Ch 12. Xc nh th i gian hai con l c n tr l i v tr trng phng (cng qua v tr cn b ng, chuy n ng cng chi u) . . . . . . . . . . . . . . . . . . 31Ch 13. Con l c n dao ng th b dy t:kh o st chuy n ng c a hn bi sau khi dy t? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31 1.Tr ng h p dy t khi i qua v tr cn b ng O . . . . . . . . . . . . . . . .31 2.Tr ng h p dy t khi i qua v tr c li gic . . . . . . . . . . . . . . . .32Ch 14. Con l c n c hn bi va ch m n h i v i m t v t ang ng yn: xc nh v n t c c a vin bi sau va ch m? . . . . . . . . . . . . . . . . . . . . . . 32Ph n3 . PHNG PHP GI I TON V DAO NG T T D N V C NG H NG C H C33Ch 1. Con l c l xo dao ng t t d n: bin gi m d n theo c p s nhn li v h ng, tm cng b i q . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33Ch 2. Con l c l n ng t t d n: bin gc gi m d n theo c p s nhn li v h ng, tm cng b i q. Nng l ng cung c p duy tr dao ng . . . . . . . 33Ch 3. H dao ng c ng b c b kch thch b i m t ngo i l c tu n hon: tm i u ki n c hi n t ng c ng h ng . . . . . . . . . . . . . . . . . . . . .34Ph n 4 . PHNG PHP GI I TON V STRUY N SNG C H C, GIAO THOA SNG, SNG D NG, SNG M 35Ch 1. Tm l ch pha gi a hai i m cch nhau d trn m t phng truy n sng? Tm b c sng khi bi t l ch pha v gi i h n c a b c sng,( t n s , v n t c truy n sng). Vi t phng trnh sng t i m t i m . . . . . . . . . . . . . . . 35 1.Tm l ch pha gi a hai i m cch nhau d trn m t phng truy n sng . .35 4. 2.Tm b c sng khi bi t l ch pha v gi i h n c a b c sng,( t n s , v nt c truy n sng) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35 3.Vi t phng trnh sng t i m t i m trn phng truy n sng . . . . . . . .35 4.V n t c dao ng c a sng . . . . . . . . . . . . . . . . . . . . . . . . . . .35Ch 2. V th bi u di n qu trnh truy n sng theo th i gian v theo khng gian 36 1.V th bi u di n qa trnh truy n sng theo th i gian . . . . . . . . . . . .36 2.V th bi u di n qa trnh truy n sng theo khng gian ( d ng c a mi tr ng...) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36Ch 3. Xc nh tnh ch t sng t i m t i m M trn mi n giao thoa . . . . . . .36Ch 4. Vi t phng trnh sng t i i m M trn mi n giao thoa . . . . . . . . . . 37Ch 5. Xc nh s ng dao ng c c i v c c ti u trn mi n giao thoa . . . 37Ch 6. Xc nh i m dao ng v i bin c c i ( i m b ng) v s i m dao ng v i bin c c ti u ( i m nt) trn o n S1 S2 . . . . . . . . . . . . . . 38Ch 7.Tm qy tch nh ng i m dao ng cng pha (hay ng c pha) v i hai ngu n S1, S2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38Ch 8.Vi t bi u th c sng d ng trn dy n h i . . . . . . . . . . . . . . . . .38Ch 9.i u ki n c hi n t ng sng d ng, t suy ra s b ng v s nt sng39 1.Hai u mi tr ng ( dy hay c t khng kh) l c nh . . . . . . . . . . . .39 2.M t u mi tr ng ( dy hay c t khng kh) l c nh, u kia t do . . . .39 3.Hai u mi tr ng ( dy hay c t khng kh) l t do . . . . . . . . . . . . .40Ch 10.Xc nh c ng m (I) khi bi t m c c ng m t i i m. Xc nh cng su t c a ngu n m? to c a m . . . . . . . . . . . . . . . . . . . . .40 1.Xc nh c ng m (I) khi bi t m c c ng m t i i m . . . . . . . . 40 2.Xc nh cng su t c a ngu n m t i m t i m: . . . . . . . . . . . . . . . .40 3. to c a m: . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41Ph n5 . PHNG PHP GI I TON VM CH I N XOAY CHI U KHNG PHN NHNH (RLC) 42Ch 1. T o ra dng i n xoay chi u b ng cch cho khung dy quay u trong t tr ng, xc nh su t i n ng c m ng e(t)? Suy ra bi u th c c ng dng i n i(t) v hi u i n th u(t) . . . . . . . . . . . . . . . . . . . . . . . . . . . 42Ch 2. o n m ch RLC: cho bi t i(t) = I0 sin(t), vi t bi u th c hi u i n th u(t). Tm cng su t Pm ch . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42Ch 3. o n m ch RLC: cho bi t u(t) = U0 sin(t), vi t bi u th c c ng dng i n i(t). Suy ra bi u th c uR (t)?uL(t)?uC (t)? . . . . . . . . . . . . . .42 5. Ch 4. Xc nh l ch pha gi a hai ht t c th i u1 v u2 c a hai o n m ch khc nhau trn cng m t dng i n xoay chi u khng phn nhnh? Cch v n d ng? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43Ch 5. .o n m ch RLC, cho bi t U, R: tm h th c L, C, : c ng dng i n qua o n m ch c c i, hi u i n th v c ng dng i n cng pha, cng su t tiu th trn o n m ch t c c i. . . . . . . . . . . . . . . . . . . 43 1.C ng dng i n qua o n m ch t c c i . . . . . . . . . . .