Tong Hop Mot So Van de Moi Hay Kho Trong Cac de Thi Thu Dh 2014.Thuvienvatly.com.73452.40254 (1)

7/22/2019 Tong Hop Mot So Van de Moi Hay Kho Trong Cac de Thi Thu Dh 2014.Thuvienvatly.com.73452.40254 (1)

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TNG HP MT SVN MI HAY KH TRONG CC THI THH 2014

NGUYN B LINH THPT TRN HNGO THANH XUN.

I. DAO NG C

Cu 1: (Chuyn H Vinh 2014 L1) Mt con lc l xo gm vt nhkhi lng m = 0,1 kg v l xo ccng k = 100 N/m. Tvtr l xo khng bin dng, ko vt n vtr l xo gin 5 cm ri thnhchovt dao ng. Hs ma st trt gia vt v mt phng ngang l .05,0 Coi vt dao ng tt dn chm.

Tc ca vt khi n i c 12 cm ktlc thl

A. 1,39 m/s. B. 1,53 m/s. C. 1,26 m/s. D. 1,06 m/s.Hng dn :

Cu 2: (Chuyn H Vinh 2014 Ln 3) Mt con lc l xo t nm ngang gm vt M = 100g v l xoc cng k = 10N/m ang dao ng iu ha xung quanh vtr cn bng vi bin A = 10cm. Khi M

i qua vtrc li x = 6cm ngi ta thnhvt m = 300g ln M (m dnh cht ngay vo M). Sau hm

v M dao ng vi bin xp x

A. 6,3 cm. B. 5,7 cm. C. 7,2 cm. D. 8,1 cm.Hng dn :

Cu 3: Chuyn H Tnh 2014 - Ln 1


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Hng dn :


Hng dn :



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Cu 6: (Chuyn H Tnh 2014 - Ln 2) Con lc l xo treo thng ng, gm l xo c cng k v vtnhc khi lng m = 400 g. Bit rng trong mt chu k, thi gian lc n hi ca l xo thc hin cng

m bng 0,2 s. k c gi trbng

A. 256 N/m. B. 98,7 N/m. C. 225 N/m. D. 395 N/m.Hng dn :Trong mt chu k thi gian lc n hi l xo thc hin cng m l T/2 = 0,2s => T = 0,4s =>= 5rad/s => k = m2= 100N/m.

Cu 7: (Chuyn H Tnh 2014 - Ln 2) Mt con lc l xo dao ng dc theo trc thng ng ca n viphng trnh x = 4,5cos(20.t/3) cm, t tnh bng s. Trong mt chu k, khong thi gian m lc ko v ngc

hng vi lc n hi tc dng vo vt l

A. 0,1 s. B. 0,05 s. C. 0,15 s. D. 0,2 s.Hng dn : Chn trc Ox hng xung. Ta c lc ko v: F = -kx.Lc n hi l xo: Fh= -k(l0+x). F v Fhngc hng nhau: F.Fh x(l0+x) < 0 => -l0< x < 0.l0= g/

2= 0,0225m = 2,25cm; T = 0,3s.Khong thi gian trong mt chu k m F v Fhngc hng nhau: t =T/6 = 0,05s.

Cu 8: (Chuyn H Tnh 2014 - Ln 3) Mt vt tham gia ng thi hai dao ng iu ho cngphng, cng tn sv c dng phng trnh x1= 3 cos(4t + 1) cm, x2= 2cos(4t + 2) cm vi 0 1

2. Bit phng trnh dao ng tng hp x = cos(4t + /6) cm. Gi tr1l

A. 2/3. B. /6. C. /6. D. 2/3.Hng dn : Ta c 1 2 2 11 3 4 2 3.2.cos 5 5 .

M: 1 21 1 1 1

1 2

3 sin 2sin 1 5 5tan tan 3sin 2 3 sin 3cos 2cos

6 6 63 cos 2cos 3

.

11 1

1

sin 2tan 3

cos 3

.

Cch 2 : Th p n.

Ta c : 2 11 3 4 2. 3.2.cos ; thay ln lt cc p n ng vi 1vo, p n no thamn iu kin bi th ly nghim .Cu 9: Chuyn H Tnh 2014 - Ln 4

4,5 x-4,5

-2,25 O

T/12

T/12


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Hng dn : Chn D.

max

max

5 A 3 5A sin .

4 sin 30sin sin

4 12 4

3A4 2 4

A 10

* Khi A = Amax/2 = 5(cm) ta c : 05 A 5

1053 3sin sin sin

6 4 4

Khi

22

A 5A 5 3

sin30sin 105 15

Cu 10:(Chuyn KHTN 2014 - Ln 1) Cho hai con lc l xo ging ht nhau. Kch thch cho hai con lc

dao ng iu ha vi bin ln lt l 2A v A dao ng cng pha. Chn gc th nng ti vtr cn

bng ca hai con lc. Khi ng nng ca con lc thnht l 0,6J th th nng ca con lc thhai l 0,05 J.

Hi khi th nng ca con lc thnht l 0,4 J th ng nng ca con lc thhai l bao nhiu?

A. 0,1 J. B. 0,4 J. C. 0,6 J. D. 0,2 J.Hng dn : Chn A

1 2 t1 t21 2

1 2 1 21 2

1 2 2 2 t2

t1t1 t2 2 2 t2

x 2A cos t x A cos t W 4Wx 2x;

v 2v W 4Wv .2A sin t v .A sin t

K hi W 0,6J W 0,15 J W W W 0,15 0,05 0,2 J

WK hi W 0,4 J W 0,1 J W W W 0,1 J

2

Cu 11:(Chuyn KHTN 2014 Ln 4) Mt con lc n c khi lng vt nng l m, si dy mnh cchiu di l. Tvtr cn bng ko vt sao cho dy treo hp vi phng thng ng gc 0= 60

0ri th

nh. Ly g = 10m/s2, bqua mi lc cn. Trong qu trinh chuyn ng th ln gia tc ca con lc c

gi trnhnht bng:

A.2

103

(m/s2). B. 210 5 m / s3

C. 0. D. 2310 m / s2

.

Hng dn :

22 2t n t n 0

22 2

min min

va a a a gsin ; a 2g cos cos

1a g sin 2g cos g 3cos 4 cos 2

2

b 4 2 4 2 2a cos a g 3. 4. 2 g

2a 6 3 9 3 3

l

5/4

/12

A2

A


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Cu 12:(Chuyn KHTN 2014 - Ln 4) Cho mt con lc n c vt nng 100g, tch in 0,5mC, dao ngti ni c gia tc g = 10 m/s2. t con lc trong in trng u c vc t in trng nm ngang, ln

2000 / 3 (V/m). a con lc vv tr thp nht ri thnh. Tm lc cng dy treo khi gia tc ca vt

nng cc tiu.

A. 2,19 (N) B. 1,46 (N). C. 2 (N). D. 1,5 (N).

Hng dn :

0

2

00

qE* VTCB khi coien trng : tan = 3 60mg

g* Gia toc trong trng hieu dung g' = 20 m / s

cos* a vat ti vtr thap nhat roi thacho dao ong 60

* Gi a toc cua vat k hi dao o

22

0

2mi n

0

ng trong trong tr ng bieu kien :

a = g ' sin 2g ' cos cos

2a 3cos 4 cos 2 a khi vachkhi cos =

3* L c cang day khi o: T = mg' 3 cos 2 cos 2 N

Cu 13:(Chuyn L Khit 2014)Mt con lc n gm mt si dy mnh, khng dn v c chiu di l,vt nhc khi lng m. Tvtr cn bng, ko vt nhsao cho dy treo hp vi phng thng ng mt

gc 450ri thnh. Gia tc trng trng l g, mc th nng ti vtr cn bng, bqua sc cn khng kh.

ln cc tiu ca gia tc vt nhtrong qu trnh dao ng l :

A. g. B.1

g3

. C.2

g3

. D. 0.

Hng dn : Xt vt vtr m dy treo lch so vi phng thng ng gc .ng nng ca vt bng gim th nng ca n nn c :

2 2

2

22 2 2t n

2min min

min

mv v 2mgl cos cos 2g cos

2 l 2

2a a a gsin 2g cos g 3cos 4 2 cos 3

2

4 2 2 2 3a khi 3cos 4 2 cos 3 cos a g

2.3 3 3

Cu 14:(Chuyn L Li 2014 - Qung Tr) Dng c o khi lng trong mt con tu v trc cu togm mt chic ghc khi lng m c gn vo u ca mt chic l xo c cng k = 480 N/m. o

khi lng ca nh du hnh th nh du hnh phi ngi vo gh ri cho chic gh dao ng. Ngi ta o

c chu k dao ng ca gh khi khng c ngi l T0= 1 s cn khi c nh du hnh l T = 2,5 s. Khi

lng nh du hnh l

A. 80 kg. B. 63 kg. C. 75 kg. D. 70 kg.Hng dn gii:

- Nhn xt:Chic ghc cu to ging nh mt con lc l xo treo thng ng, ghpha trn, l xo phadi. Gi khi lng ca ghl m (kg), ca ngi l m0(kg).


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-Khi cha c ngi ngi vo gh: 0 2 1m

Tk

(1).

-Khi c ngi ngi vo gh: 02 2,5m m

Tk

(2).

- T(1) v (2), ta c:

0 2 2

200

2 2,52,5 1

63 ( 10)2 2

2 1

m m

mkm kg

km

k

Cu 15:(Chuyn SP1 2014 - Ln 1) Mt con lc n chiu di dy treo =50cm, c treo trn trn mttoa xe. Toa xe c th trt khng ma st trn mt phng nghing gc =300 so vi phng ngang. Ly

g=9,8m/s2. Chu k dao ng vi bin nhca con lc khi toa xe trt tdo trn mt phng nghing l

A.1,53 s. B. 1,42 s. C.0,96 s. D. 1,27 s.Hng dn :

2

2 2 0

Gi a toc toa xe trt khong ma sat tren doc : a=gsin =4,9 m / s

l lChu k dao ong khi o: T '=2 2 1,53 s

g ' g a 2gacos120

Cu 16:*Mt dao ng iu ha vi bin 13 cm. Lc t = 0 vt ang bin dng. Sau khong thi gian t(kt lc ban u chuyn ng) th vt cch O mt on 12 cm. Vy sau khong thi gian 2t (kt lc

ban u chuyn ng) vt cch O mt on bao nhiu?

A. 9,15 cm B. 5 cm C. 6 cm D. 2 cm

HD: 12

22

2

0 13cos

: 12 13cos

122 : 13cos2 13 2 cos 1 13 2 1 9,15

13

V t va t ang bien dng nen x t

Vtr cua vat tai thi i em t cachVTCB oan x t

Vtr tai t ca chVTCB oan x t t cm

Cu 17:Chuyn H Vinh 2013 ln 4

Hng dn : Chn B.

Cch 1

-Hai l xo mc ni tip L xo tng ng c cng k = k1/3.

- Khi thvt tbin, thi im ln u vt c ng nng bng th nng nnA

x 6 22

.

- Khi gicht im ni hai l xo, chcn l xo 2 hot ng, nhng c mt phn nng lng bnht

trong l xo 1.

- L xo l tng nn dn u trn tng vng. Do k1= 2k2nn khi l xo 1 dn x1th l xo 2 dn 2x1.

- Lc vt x = 62 cm tc dn x1+ 2x1= 62 x1= 22 cm.(l xo 1 dn x1)


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-Theo nh lut bo ton nng lng : 2 22

2 1 1 11

k A k xkAA 4 5 cm

2 2 2

Cch 2 Cch ny ngn gn v dhiu hn

- knt= 2k2/3 ;2

t t nt

A 1Khi W W x 6 2 & W W k .x

22

- Gic nh im ni hai l xo : Chcn l xo 2.

- Lc vt v tr ng nng bng th nng : 1 2 1 21 2 1 2

x x 6 2 x 2 2 cm & x 4 2 cmk 2k 2x x

- p dng LBT c nng ta c : 2 2 2 t nt 2 2 2 2 21 1 1

W W k x k x k A A 4 5 cm2 2 2

II. SNG CCu 18:(Chuyn H Vinh 2014 L3) Hin tng giao thoa sng trn mt nc vi hai ngun 21 S,S cng

bin , ngc pha, .cm13SS 21 Tia yS1 trn mt nc, ban u tia yS1 cha .SS 21 im Clun trn tia

yS1 v .cm5CS1 Cho yS1 quay quanh 1S n vtr sao cho CS1 l trung bnh nhngia hnh chiu ca

chnh n ln 21SS vi .SS 21 Lc ny C trn vn cc i giao thoa th4. Svn giao thoa cc tiu quan st

c l

A. 13. B. 10. C. 11. D. 9.

Hng dn : * c l trung bnh nhn ca a v b th c a.b - Hai ngun ngc pha, C thuc cc i th4 ng vi k = - 4 hoc k = 3.

Cu 19:(Chuyn H Tnh 2014 - Ln 3)Ti im O trong mi trng ng hng, khng hp thm,c mt ngun m im vi cng sut pht m khng i. Hai im M, N trong mi trng sao cho OM

vung gc vi ON. Mc cng m ti M v N ln lt l LM= 50 dB, LN= 30 dB. Mc cng m

ti trung im ca MN l

A. 40 dB. B. 35 dB. C. 36 dB. D. 29 dB.


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Hng dn:

2 220 20 lg 10 101

2 2, , ;

M N

ONL L dB ON OM OM ON

OM OP OM M N O P PO OP PM PN

10120lg 20lg 14 36

2M P POP

L L dB L dBOM

Cu 20:(Chuyn H Tnh 2014 - Ln 3)mt cht lng c hai ngun sng A, B cch nhau 19 cm, daong theo phng thng ng vi phng trnh l uA= uB= acos(20.t) (vi t tnh bng s). Tc truyn

sng trn mt cht lng l 40 cm/s. Gi M l im mt cht lng gn A nht sao cho phn tcht lng

ti M dao ng vi bin cc i v cng pha vi ngun A. Khong cch AM l

A. 4 cm. B. 3 cm. C. 2 cm. D. 5 cm.Hng dn :Cch 1M dao ng cc i: 2 1 1d d k , = 4cm.

S ng cc i: 1 4,75 4,75AB k AB k .

Gn A nht th k1= 4 2 1 16d d (1).

Phng trnh sng ti M: 1 22 cos 20Md d

u a t

.

M cng pha vi hai ngun: 1 2

2 1 2 2 22 2 8d d

k d d k k

(2).

T(1) v (2) suy ra: d1= 4k2 8. M gn A nht => k2= 3 => d1= 4cm.Cch 2

M 1 2 1 2

1 2

1 2

1 2 11 1 2

1 2 2

2* v.T 40. 4 cm .

20* Phng trnh song ti M :

u 2acos d d .cos 20 t d d

cos d d 1* ieu ki en M dao ong cc ai vacung pha vi nguon :

d d 2k

d d 2kd 2k 2k

2d d 2k

1min min 1min

k '.2

Dethay k ' chan d k ' 2 d 2. 4 cm2

Cu 21:Chuyn H Tnh 2014 - ln 4

Hng dn : Chn DCch 1.

A B B AB M

r r r rOM OB M B r r

2 2

A O

M B

A B

M

O

M

N

P


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2

0,3 0,3M B AA M M A B A

A

2

BA B B B

A

r r rL L 10 lg r 10 r r 2.10 1 r

r 2

rL L 10 lg 50 L 13, 96 dB L 36 dB

r

Cch 2

+ Cng m ti im cch ngun m khong R l I =24 R

P

; Vi P l cng sut ca ngun

M

A

II =

2

2

A

M

RR ; LA LM= 10lg

M

A

II = 10lg

2

2

A

M

RR = 6

2

2

A

M

RR =100,6

A

M

RR = 100,3

+ M l trung im ca AB, nm hai pha ca gc O nn: RM= OM =2

AB RR

RB= RA+ 2RM= (1+2.100,3)RA-----> 2

2

A

B

R

R= (1+2.100,3)2

B

A

I

I=

2

2

A

B

R

R; LA- LB= 10lg

B

A

I

I= 10lg

2

2

A

B

R

R= 20 lg(1+2.100,3) = 20. 0,698 = 13,963 dB

LB= LA 13,963 = 36,037 dB 36 dB

Cu 22:(Chuyn KHTN 2014 - Ln 1) Hai ngun m ging nhau c t ti hai im A, B cch nhau

mt khong AB = L = 2m, pht cng mt m n, cng tn s1500Hz. Vn tc truyn m trong khng

kh l v = 340m/s. I l trung im ca AB, im O trn ng trung trc AB sao cho d = OI = 50m. TO

v ng Ox song song vi AB. Xc nh khong cch ca hai im gn nhau nht trn Ox m nghe thy

m nhnht. Githit


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* Khi tip tc nc vo ng, ct khng khgim dn :

v m ' m 'l ' m ' 0,7 m ' 7 m ' 1,3,5

4f 10 10

Nh vy, cn 3 gi tr cho m to nht.Cu 24:(Chuyn KHTN 2014 - Ln 4) Mt m thoa c tn s dao ng ring 850Hz c t st mtming ng nghim hnh tr y kn t thng ng cao 80cm. dn nc vo ng nghim n cao30cm th thy m c khch i ln rt mnh. Bit tc truyn m trong khng kh c gi trnm trong

khong t 300m/s n 350m/s. Hi khi tip tc nc thm vo ng th c thm my v tr ca mc

nc cho m c khch i rt mnh?

A. 2. B. 3. C. 1. D. 4.

Hng dn :

-Khi dn nc vo ng nghim n cao 30cm th thy m c khuch i rt mnh, c ngha l

khi hin tng sng dng xy ra, m nghe c to nht do ti y ng thnh mt nt sng, ming ng

hnh thnh mt bng sng. Mt khc nc cao 30cm th ct khng kh cao 50cm.-Khi :

1 1 0,50, 5 k v k v

4 2 4f 2f 1 1k

4f 2f

0,5300 v 350 1, 93 k 2,33 k 2 v 340 m / s

1 1k

4f 2f

40 cm

- Khi tip tc nc vo, chiu di ct khng kh gim dn :

0 k 0, 5 0,5 k 2 k 0,14 2

Vykhi thm nc vo th c thm 2 vtr lm cho m khuych i rt mnh.

Cu 25:(Chuyn L Khit 2014) Trn mt nc c hai ngun pht sng A v B cch nhau 24 cm,phng trnh sng ln lt l 5Au cos(20 t + ) (mm) v 5Bu cos(20 t) (mm). Sng truyn trn mt

nc n nh vi vn tc 40 cm/s v khng b mi trng hp th. Xt ng trn (C) tm I bn knh R =

4 cm vi I l im cch u A, B mt on 13 cm. im M nm trn (C) xa A nht dao ng vi bin

gn bng gi trno nht ?

A. 10 mm. B. 9,44 mm. C. 6,67 mm. D. 5 mm.Hng dn : Gi O l trung im AB


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2 2

1 2

M

IO 13 12 5 cm

M laiem xa A nhat nen M lagiao iem cua A I va I ;R 4cm AM 13 4 17 cm

M B 10,572 cm

d d 17 10,572Bien odao ong tai M : A 2A .cos 2.5.cos 9,44 mm

2 4

Cu 26:(Chuyn Nguyn Hu2014 - Ln 2)Hai ngun kt hp A v B dao ng theo phng vunggc vi bmt cht lng vi phng trnh cos .A Bx Ax t Vtrn bmt cht lng mt elip nhn A v

B l tiu im. Hai im M v N nm trn elip v nm trn hai ng dao ng cc i lin tip. So snh

pha dao ng ti M v N, ta c

A. M v N lch pha .4

B. M v N ngc pha. C. M v N cng pha. D. M v N lch pha .

2

Hng dn :

M 2 1 1 2

1M 2 M 1N 2N

1M 2 M 1N 2 N

Phng tr nh song tai M thuoc mien giao thoa:

u 2A cos d d cos t d d

* M ,N thuoc mot el ip d d d d 2a hang so

cos t d d cos t d d

* M , N thuoc hai

2M 1M 2M 1M 2N 1N

2N 1N

d d kcc ai l ien ke: cos d d cos d d

d d k 1

Do o: M vaN ngc pha!

Cu 27:Ngun m S1 cch bc tng mt khong SH = 1m. My thuS2 cch tng mt khong S2I = 9m; HI = 5m. Tnh tn s cc tiu m ghi c l cc i? Vn tc truyn m trong khng kh l 340 (m/s).

A. 194,3 Hz. B. 97,2 Hz.C. 105,7 Hz. D. 86,34 Hz.

Hng dn :m phn x ln tng nh nh sng phn x ln gng, nhng khngmt na bc sng do y l sng dc. m phn x giao thoa vi mtruyn thng t S1n S2.im phn x l J chia HI theo t l 9:1 (tam gic ng dng) AB v JBgn song song nn c th giao thoa.

AJ + JB AB = 1,75m.

Cc i nu :340

k k. 1,75 vi k = 1 f = 194,3 Hzf

Cu 28:Hai ngun kt hp S1, S2cch nhau khong S1S2= 2d c tns50Hz gy ra sng trn mt nc trong mt chu ln. Ngi ta t

mt ci a nha trn bn knh r = 1,2 cm ln y nm ngang ca

chu, tm a l S2. Vn tc ca sng ch nc su l v1= 0,4 m/s;


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ch nc nng hn v c a, vn tc l v2< v1. Tm gi trln nht

ca v2, bit ng trung trc ca S1S2l mt ng nt (bin dao

ng cc tiu) v r < d.

A. 0,2 m/s. B. 0,1 m/s. C. 0,3m/s. D. 0,15m/s.

Hng dn: T = 0,02 s.Sng i tS1n A mt thi gian t1= d/v1Sng i tS2n A mt thi gian : t2= r/v2+ (d r)/v1t = t2 t1= 0,012/v20,03. Trung im ca S1S2l cc tiu giao thoa nu hai sng ti ngc pha nhau.

k 02 2 max2 T 0,6

t t 2k 1 t 2k 1 v v 0,3 m / sT 2 k 2

Cu 29:Trn mt h nc yn lng, ti hai im A v B cch nhau 3,0m c hai ngun ng bgingnhau dao ng theo phng vung gc vi mt nc vi chu k l 1,00 s. Cc sng sinh ra truyn trn mt

nc vi tc 1,2m/s. O l trung im ca on AB. Gi P l mt im rt xa so vi khong cch l= AB

v to gc POx vi Ox l trung trc ca AB. Khi P nm trn ng cc tiu gn trung trc ca AB

nht, gc c ln:

A. 11,530. B. 23,580. C. 61,640. D. 0,40.Hng dn : = 1,2m

P rt xa ngun, da vo hnh v ta thy :d2 d1= d = AB.sin

P thuc cc tiu giao thoa :d2 d1= d = AB.sin= (k + 0,5)

Theo bi k = 0 sin= 0,2 = 11,530.

III. IN XOAY CHIU.Cu 30:(Chuyn H Vinh 2014 - Ln 1)Trong qu trnh truyn ti in nng i xa, in nng nitiu th khng i. Coi cng dng in trong qu trnh truyn ti lun cng pha vi in p. Ban u

gim in p trn dy bng n ln in p ni truyn i. Sau , ngi ta mun gim cng sut hao ph

trn ng dy i m ln th phi tng in p ni truyn i ln bao nhiu ln?

A. .mn/]nm[ B. .m/]n)n1(m[ C. .m/)]n1(nm[ D.

.mn/]1)n1(mn[

Hng dn :


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Cu 31:(Chuyn H Vinh 2014 L1) t in p ft2cos2Uu (trong U khng i, f thay ic) vo hai u on mch gm R v C mc ni tip. Khi tn sl 1f hoc 12 f3f th hscng sut

tng ng ca on mch l 1cos v 2cos vi .cos2cos 12 Khi tn sl 2/ff 13 hscng sut

ca on mch 3cos bng

A. .4/7 B. .5/7 C. .4/5 D. .5/5

Cu 32:(Chuyn H Vinh 2014 L3) t mt hiu in thxoay chiu )V(t100cos2120u vo haiu mt mch in xoay chiu ni tip gm 1R v cun dy thun cm L th u lch pha so vi i l ,4

ng thi .A25,1I Sau , ni tip thm vo mch trn in tr 2R v tC th cng sut ta nhit trn

2R l .W90 Gi trca 2R v C phi l

A. ).F(10v40 4 B. ).F(10v50 4 C. ).F(10.5,2v40 4 D.

).F(10.5,2v50 4

Hng dn :Cch 1 : Cch gii ny c v "t o"

Cch 2 :

* Mch R1L c 1 LZ U

R Z 402 2.I

* Mch R1LR2C

222 2

R2 2 22 2 2 2

1 2 L C 2 C

2 2 2 22 C 2 2 C

C

120 RUP I R .R 90

R R Z Z 40 R 40 Z

40 R 03 40 R 3 40 Z 480R 40 R 3. 40 Z 0

40 Z 0

Cu 33:(Chuyn H Vinh 2014 ln 3)t hiu in thxoay chiu )V()t100cos(Uu 0 hai uon mch ni tip theo th t gm 21 R,R v cun thun cm c t cm L thay i c. Bit

.3200R2R 21 iu chnh L cho n khi hiu in thtc thi gia hai u on mch cha 2R v L

lch pha cc i so vi hiu in th hai u on mch. Gi trca tcm lc l

A. ).H(/2L B. ).H(/3L C. ).H(/4L D. ).H(/1L Hng dn:


14/30

Cu 34:(Chuyn H Vinh 2014 ln 3) C ba dng cgm in trthun ,30R cun cm thun Lv t in C. t in p xoay chiu )V()tcos(Uu 0 ln lt vo hai u on mch ni tip gmRL v RC khi cng dng in trong mch )A()7tcos(6i1 v ).A()2110tcos(6i2 t

in p trn vo hai u on mch RLC mc ni tip th cng sut mch in lc bng

A. .W960 B. .W720 C. .W480 D. .W240 Hng dn :

01 02 RL RC

2 21 2 1 2 L C

RL RC

i1 i 2 2 1

2 2RL L 1 RL

2

L C max

I I Z Z

R R Rcos ; cos Z Z 10 3

Z Z 2 6 3

3

* Z R Z 20 3 U I .Z 60 6 V

U* M ach RLC Cong hng do Z Z P 720 W

R

Cu 35:(Chuyn H Vinh 2014 ln 3) Mt my pht in xoay chiu mt pha c cng sut P = 4932kW cung cp in thp sng bnh thng 66 bng n dy tc cng loi W60V220 mc song song

vi nhau ti mt ni kh xa my pht. Coi in tr cc on dy ni cc bng vi hai dy ti l rt nh

v u cng pha i. Hiu in thhiu dng hai cc ca my pht bng

A. 274 V. B. 254 V. C. 296 V. D. 300 V.Hng dn :

Cu 36:(Chuyn H Tnh 2014 - Ln 1)

Hng dn :


15/30

Cu 37:Chuyn H Tnh 2014 - Ln 1

Hng dn :

Cu 38:(Chuyn H Tnh 2014 - Ln 2) in p u = U0cos(100.t) (t tnh bng s) c t vo hai uon mch gm cun dy v t in mc ni tip. Cun dy c tcm L = 0,15/ (H) v in trr =

5 3 , t in c in dung C = 10-3/(F). Ti thi im t1(s) in p tc thi hai u cun dy c gi

tr 15 V, n thi im t2= t1+ 1/75 (s) th in p tc thi hai u t in cng bng 15 V. Gi trca U0

bng

A. 15 V. B. 30 V. C. 15 3 V. D. 10 3 V.

Hng dn:Cch 1


16/30

1

2

2

Ld d A B A B

0AM 1d t

AB C C 0C

0C 1 0C 1C t

C t

Z 1tan 3 tan

r 3 63

u 15 U cos 100 t 16

2 2* u nhanh pha hn u goc u U cos 100 t

3 3

1 2 2u 15 U cos 100 t U cos 100 t

75 3 3

* Dethay u

1 1 2

0C 0 0d 0

2 2

0d t d t C t

0d 0C

U U ; U 3U

vau vuong pha nhau U 10 3 Vu u1

U U

Cch 2ZL= 15, ZC= 10

dZ 10 3 ; Z = 10.

Ta c U0d= 3 U0C; U0

= U0C; udnhanh pha hnuCmt gc 5/6.M1biu din trng thi udti thi im t1; N1, N2

biu din trng thi uCtithi im t1v t2.

Gc quay tthi im t1n t2l = 4/3. Ta c = 4/3 5/6 = /2. Ta c:22 2 2

0 00 0 0 0

15 15 15 151 1 10 3

3C

C d C C

U V UU U U U

Cu 39:(Chuyn H Tnh 2014 - Ln 2) on mch xoay chiu gm in trR0mc ni tip vi mthp kn X. Khi t vo hai u mch mt in p xoay chiu c gi trhiu dung U th in p hiu dng

hai u R0v hp X ln lt l 0,8U v 0,5U. Hscng sut ca mch chnh bng

A. 0,87. B. 0,67. C. 0,50. D. 0,71.

Hng dn :2 2 2 2 2

0

0

1 0,8 0,5cos 0,87

2 . 2.1.0,8R X

R

U U U

U U

.

Cu 40:(Chuyn H Tnh 2014

- L

n 2)Mt trm hp cp in cho mt nng tri thp sng cc

bng n si t cng loi c in p nh mc 220 V. Nu dng 500 bng th chng hot ng ng nh

mc, nu dng 1500 bng th chng ch t 83,4% cng sut nh mc. Coi in trca bng n khng

i. in p ra cun thcp ca my hp l

A. 310 V. B. 250 V. C. 271 V. D. 231 V.

I

UR0

U

UX

I

/3

5/

Ud

UC4/

15uU0dU0C

5/

M1

N1

N2

O


17/30

Hng dn:- Gi in p ni pht l U1; in p ni tiu thl U2. in tr cc n ni tiu th l Rtt; in tr ng dyl R.

- Th nghim 1 : Mc 500 n song song, cc n sngbnh thng:

222 tt 2

1 2 1 1

tt 1 2 2

1 1 2

2 1 2 1tt

U 220 V I UP R R

R U N N RR U IR U R U 1

N R U URU .N R U NIR

- Th nghim 2: Mc 1500 n song song, hiu sut 83,4%

222

2 tt 2tt 1

2 2

2 2tt

U '

R I ' U 'R ' P' I R R R

N N R

U ' .NI '

R

-bi : 22

1 2 22 22

1 22

P' RU ' U '. 0,834 U ' 0,834U 2

P R UU

-Khi : 2 21 tt 2 2

U ' NU I ' R U ' .R U ' 3

R

- Thay R/R v (2)vo (3) ta c phng trnh :

1 2 11 2 2 1FX570ES2 1

U U U 220U 0,834U N . 1 0,834.220 1500. 1 U 230,97 V

U N 220.500

-ny cn bsung thm cc bng trong nng tri phi mc song songCu 41:(Chuyn H Tnh 2014 - Ln 2) t in p xoay chiu u (c gi trhiu dng U v tn sf thayi c) vo hai u on mch RLC mc ni tip. Cho R/L = 100rad/s. Nu f = 50 Hz th in p uR

hai u in trR c gi trhiu dng bng U. uRtrpha /4 so vi u th ta phi iu chnh f n gi tr

f0. f0gn nhtvi gi tr no sau y ?

A. 80 Hz. B. 65 Hz. C. 50 Hz. D. 25 Hz.Hng dn : Khi f = 50Hz th UR= U => ZL0= ZC0

0

1100 /rad s

LC .

M R/L = 100rad/s => R = ZL0= 100Khi uRchm pha hn u mt gc /4

=>2 2

2 2 2100 100 100 0L C LZ Z R L L

.

Cu 42:(Chuyn H Tnh 2014 - Ln 2) Ni hai cc ca my pht in xoay chiu mt pha vo hai umt on mch RLC mc ni tip. Khi rto quay vi tc 17 vng/s hoc 31 vng/s th cng dng

in hiu dng trong mch c cng gi tr. cng dng in hiu dng trong mch t gi trcc i

th rto phi quay vi tc

A. 21 vng/s. B. 35 vng/s. C. 23 vng/s. D. 24 vng/s.Hng dn: Ta c U~n, ZL~n, ZC~1/n. Ta c:

I

Ud

U

/3

UL

UC

R Rtt

pht

U1 U2


18/30

2 22

4 2

1~

2

L C

U nI

c a bcR Z Z c ba bn n nn

.

Biu thc trong cn di mu c dng: 2 2, 1/y Ax Bx C x n .Imaxkhi yminkhi 201/ / 2x n B A . M theo Viet:

2 21 2 1 21 / 1 / /x x n n B A .

Vy: 02 2 20 1 2

1 1 1 121 v ng

2n

n n n

.

Cu 43:(Chuyn H Tnh 2014 - Ln 2)Cho mch in nh hnh v.C l t xoay cn L l cun dy thun cm. V1 v V2 l cc vn k l

tng. iu chnh gi tr ca C s ch ca V1cc i l U1, khi s

ch ca V2l 0,5U1. Hi khi

s ch ca V2cc i l U2, th s ch caV1lc l bao nhiu ? in p

xoay chiu hai u A B c gi n nh.

A. 0,7U2. B. 0,6U2. C. 0,4U2. D. 0,5U2.Hng dn: Khi V1cc i th ZC1= ZL=> UC1= UL= 0,5U1; U = UR= U1=> UR= 2UL=> R = 2ZL.

Khi V2cc i:2 2

25L

C LL

R ZZ Z

Z

;

2 2

2 2

5

2

L

C

R ZU U U U

R

.

Li c: 2

22 2 2 2 22

55 2 5 0

2 2R

R L C R R R

UU U U U U U U U U U

.

2

2 2 2

1 2 25 2 5 1 0 5 0,4

55 5R R R

R R

U U UU U U U U U

U U U

.


Hng dn : Chn A

R R R DL D

D D R D

2 1 2 1

C LR R1 2 1 1

CL

2

CC L L

U U ' U ' U '* V trong 2 trng hp R vaZ khong oi nen : cos 3

U U ' U U

* 90 cos sin

Z ZU U '* cos & cos sin tan 3 1

U U RZ

Z1 3* Tng ttan 23 R

ZT1 2 Z Z 9 Z3

C

L

d

2 2 22L C L

Z 5RZ 2R

U U 30 U* TH1 U 30 2 V

R 5 R 10R Z R Z Z

Cu 45:(Chuyn KHTN 2014 - Ln 1) t in p xoay chiu vo hai u on mch RLC ni tip,cun dy thun cm. Khi ni tt tC th in p hiu dng gia hai u in tr R tng 3 ln v dng in

trong hai trng hp vung pha vi nhau. Hscng sut lc sau bng:

C

A B

R r,L

V2V1


19/30

2 1 1 3A . B. C. D.

5 10 5 10

Hng dn : Chn DCch 1

22R 1R 1 2 1

1 2

1 2 1 2 2 1

22 2 2 2

2 2 2

2

cosR RU 3U Z 3Z cos 1

Z 3z 3

i i sin cos 22

coscos sin 1 cos 1

3

3cos 0,949

10

Cch 2

1R1

12R 1R

22R2

2 1 1 2

2 2

U 3U

UBan au : cos cos 1U 1

cos 3ULuc sau : cos

U

Theo ebai : cos sin 22

1 31 2 tan cos

3 10

Cu 46:(Chuyn KHTN 2014 - Ln 4) Cho mch in xoay chiu RLC c CR2< 2L. t vo hai uon mch mt in p xoay chiu c biu thc u = U. 2 cos(t) , trong U khng i, b in thin.

iu chnh gi trca in p hiu dng gia hai bn t t cc i. Khi UL= 0,1UR. Tnh hs

cng sut ca mch khi .

A. 117

B. 126

C. 213

D. 37

Hng dn:

Cch 1:

L C1 2 2

R

FX 570ES2 2

U 1tan . tan . tan

U 2

1tan 5 cos 0,196

26

Cch 2

2

22

C CCmax

C

L R C

22 2 2 2C C C

C

2 222

CC

L RX L RC 2 L 1

U L L C 2U L U

U 0,1U 0,1. .R L 0,1R 2Z Z

L R 1Thay 2 vao 1 .L L 1 50 51 L 5,1R

C 2 C

R R 1cos

26R 0,1R 5,1R1R L

C

Cu 47:(Chuyn KHTN 2014 Ln 4) on mch AB gm hai hp en X, Y mc ni tip, trong mihp chcha mt linh kin thuc loi in trthun, cun dy hoc t in. t vo hai u on mch

ZC(C)- ZL(C)

2

1

ZL(C)R

O

Z


20/30

AB mt in p u 100 2cos2 f t V vi f thay i c. Khi iu chnh tn s n gi trf0th in p

hiu dng gia hai u hp X v Y ln lt l UX= 200(V) v YU 100 3 V . Sau bt u tng f th

cng sut ca mch tng. Hscng sut ca on mch AB lc tn sc gi trf0l:

A. 0,5. B.1

2. C. 1. D.

32

.

Hng dn :

2

0 2 2L

* M ach tieu thucong suat nen bat buoc phai coR.

U .R* Neu mach khong coC, khi tang f tgi atr f th Z tang nen P = segi am. Trai vi e

R Z

M ach bat buoc phai coC.

2 2 2 2 2 2 2 2X Y R C X Y* X l aC Y l ag?

* U U U Y khong thechcha R v neu chcoR, mach RC luon coU U U U U

Y phai lacuon day.

* GVT

D dng tnh c :100 3 3

cos200 2

Cu 48:(Chuyn KHTN 2014 - Ln 4) Mch in xoay chiu gm bin tr, cun dy khng thun cmv t in ghp ni tip. t vo hai u on mch in p c biu thc l u U 2 sin t V . Trong

U v khng i. Khi bin trR = 75 th cng sut tiu thtrn bin tr t gi trln nht. Xcnh

in trthun ca cun dy v tng trca mch AB; bit rng chng u c gi trnguyn.

A. r = 15 v Z = 100. B. r = 35 v Z = 105.

C. r = 21 v Z = 120. D. r = 12 v Z = 157.

Hng dn:

2 22 2 2L C L C

R max

2 2

L C

2 2

2

R r Z Z R r Z ZPr R 75

* Z R r Z Z 2R R r 150 75 r 5 6 75 r

* Do r vaZ nguyen nen 75 + r = 6k r 6k 75

* Vi 0 < r = 6k 75 75 3, 53 k 5 k 4 r 21 Z 120

UX=200

YU 100 3

U=100


21/30

Cu 49:(Chuyn khtn 2014 - Ln 4) Ti mt im M c mt my pht in xoay chiu mt pha c cngsut pht in v hiu in thhiu dng hai cc ca my pht u khng i. Ni hai cc ca my pht

vi mt trm tng p c hs tng p l k t ti . T my tng p in nng c a ln dy t i cung

cp cho mt xng c kh cch xa im M. Xng c kh c cc my tin cng loi, cng sut khi hot

ng l nh nhau. Khi hsk = 2 th xng c kh c ti a l 120 my tin cng hot ng. Khi hsk

= 3 th xng c kh c ti a 130 my tin cng hot ng. Do xy ra sctrm tng p, ngi ta phi

ni trc tip dy ti in vo hai cc ca my pht in. Khi xng c kh c th cho ti a bao nhiumy tin cng hot ng. Coi rng chc hao ph trn dy ti in lng k. in p v dng in trn

dy ti in lun cng pha.

A. 120 B. 84. C. 93. D. 66.

Hng dn :

-Khng dng tng p : P P kx 1 k la somay,x lacong suat tieu thumot may

-Tng p vi hs2 (hao ph gim 4 ln) : P = P/4 + 120.x (2)

-Tng p vi hs3 (hao ph gim 9 ln) : P = P/4 + 130x (3)

- T(2) v (3) 5P = 690xx= P/138 ; P = 12P/23 (4). Thay vo (1) c k = 66

Cu 50:Chuyn Nguyn Hu2014 - Ln 2 on mch AB gm hai on mch AM v MB mc nitip. on mch AM c in tr 1 20R mc ni tip vi t in C, on mch MB c in tr 2R mc

vi cun dy thun cm c tcm L. t vo hai u on mch AB in p xoay chiu c gi trhiu

dng v tn s khng i th cng dng in tc thi sm pha12

so vi in p ca hai u on

mch. in p gia hai u on mch AM v MB lch pha2

v gi trhiu dng ca in p gia hai

im A, M gp 3 ln gi trhiu dng ca in p gia hai im M, B. Gi trca 2R l

A. 30 B. 20 C. 20 3 D.20

3

Vgin :t Uab=U (Hiu dng). Tam gic AMB vung ti Mnn

1

2

2 21 2

1 1

2.

3tan / / 6

2.cos

4 2

3 1 20

2 2 3 3

AM R

AM

R MB

RR

R

U U

MB AM U U

U U

U RU U R

U R

Cu 51:(Chuyn Nguyn Hu2014 - Ln 3) on mch AB gm hai on mch AM v MB mc nitip. on mch AM gm in tr 1R mc ni tip vi t C c in dung

310

2F

, on mch MB l cun

A

M

B

N

1RU

2RU

/12

H


22/30

dy c in tr 2R v t cm L. t gia hai u on mch AB in p xoay chiu

2 cos100 06 Vu t th in p hiu dng gia hai im A v M l 24 5V, nu ni tt hai u tC

bng dy dn c in tr khng ng k th in p hiu dng ca hai on AM v MB ln lt l

20 2Vv 20 5 .V Hscng sut trn mch AB khi cha ni tt l

A. 0,86 B. 0,81 C. 0,95 D. 0,92Zc=200 . Khi ni tt C. nh l hm scos tam

gic AMB2 2 2

2 ' 1 2

' 2

1 1cos cos

2. . 10 10

' .cos 10 2 2

' .sin 30 2 3

AM BM

AM BM

R M B

L M B L

U U U

U U

U U V R R

U U V Z R

Ban u:

2 2 2 21 1

2 2 221 2

1 1

2 2 2 2 2 21 1 1 1 1

1

2

5 9 3.

4 2

5 5 18 4 12 13 12 0

100200 300 tan os 0,95

300

C CAM

L CC

C C C C C

C L

R Z R ZU

U R R Z ZR R Z

R Z R Z R Z R R Z Z

R Z Z c

Cu 52:t in p xoay chiu u=200 2cos(t+ )V6

vi bin thin vo hai on mch RLC ni tip

vi cun dy thun cm. Thay i n khi ts9

41L

C

Z

Z th in p hiu dng hai u t in cc i.

Gi trcc i l

A. 200 V. B. 200 2 V . C. 205 V. D. 250 V.

Thay i C sao cho Ucmax khi max 21

C

C

L

UU

f

f

Trong 21

2CL R

L C l tn s khi in th trn

t t gi tr cc i.2

1 1

2

L C L R

C

l tn s khi hiu in th trn cun dy t cc i. =>

21.L C oLC Vi 0 tn s khi trong mchxy ra hin tng cng hng.

Vy:2 2

12 2

C

L

f C L R R C

f L C L

Vi

A

M

B

N

1RU

2RU

M

B


23/30

2 2 2 2 2

2 64 64 32 3229 9 2 9 41

LL C L

Z L R C LCR Z Z Z

L

Vy max 2 2200

2059

1141

C

C

L

UU V

f

f


24/30

IV. DAO NG IN TCu 53:(Chuyn H Tnh 2014 - Ln 1)

Hng dn :

Cu 54:(Chuyn H Tnh 2014 - Ln 3)Cho mch dao ngLC ang c dao ng in tt do, intch cc i trn mt bn tl Q0. Dy dn ni mch dao ng c tit din S, lm bng kim loi c mt

lectron tdo l n. Gi v l tc trung bnh ca cc lectron i qua mt tit din thng ca dy cng

mt thi im. Gi trcc i ca v l

A. vmax= .

e.n.S

LCQ0 B. vmax= .

LCQ

e.n.S

0

C. vmax= .

Q

LCe.n.S

0

D. vmax= .

LCe.n.S

Q0

Hng dn : 00 0Q

I QLC

. 00 max maxQdq

i enSv I enSv vdt enS LC

.

Cch 2 Ta c: 0 0max max 0 0 max

Q QI neS.v v khi I I Q v

neS neS LC

Cu 55:(Chuyn KHTN 2014 Ln 4) Cho mch in nh hnh v,ngun c sut in ng E = 12V, in tr trong r = 1, t in c in

dung C = 100F, cun dy c h s t cm L = 0,2(H) v in tr l R0=

5; in tr R = 18. Ban u K ng, khi trng thi trong mch n

nh ngi ta ngt kha K. Tnh nhit lng ta ra trn in tr R trong

thi gian t khi ngt K n khi dao ng trong mch ngt hon ton (b

qua mt mt nng lng do bc x in t)

A. 28,45mJ. B. 5,175mJ. C. 25mJ. D. 24,74mJ.

Hng dn :

-Khi ng kha K, ngun in cung cp dng in cho cun dy v np in cho t.

-Nng lng ca mch dao ng khi l : 2 2ttrng ien trng 01 1

W W W L I CU2 2

2 260

0

EI 0,5 A 1 1R R r W .0, 2. 0,5 .100.10 . 11,5 31,61 mJ

2 2U E Ir 12 0,5.1 11, 5 V

- Nhit lng ta ra trn R : R R0

RR0

R0 0

Q W Q QR

Q .Q 24, 74 mJQ RR R

Q R

E,r C

R0, L

k

R


25/30

Cu 56:(Chuyn Nguyn Hu2014 - Ln 2) Mt mch dao ng l tng gm cun cm thun c tcm L khng i v t in c in dung C thay i c. Khi in dung ca tl 1Cth tn s dao ng

ring ca mch l 30 MHz. Tgi tr 1Cnu iu chnh tng thm in dung ca tmt lng C th tn

s dao ng ring ca mch lf. Nu iu chnh gim t im ca tmt lng 2 C th tn sdao ng

ring ca mch l 2f. Tgi tr 1Cnu iu chnh tng thm in dung ca tmt lng 9 C th chu k

dao ng ring ca mch l

A. 840

.103

s B. 84

.103

s C. 820

.103

s D. 82

.103

s

Hng dn :

60

1

11 2 1

11 1

6 80

11

1f 30.10

2 L C

C C1 1f f ; f 2f 2 C 3 C 1

C 2 C2 L C C 2 L C 2 C

f1 1 20f ' 2 f ' 15.10 T ' .10 s

f ' 32 L .4C2 L C 9 C

Cu 57:Chuyn H Vinh 2013 ln 4

Hng dn : Chn A.

2 201 02

1 2

2 21 201 02

1 21 2

CU CUW 4W 4 NL mach1gap 4 lanNL mach 2.

2 2

i 2iL I L I* Do i luon cung pha i va 42 2 u 2u

222 2 111 1

1 2 12

2 2

2 2

1 21 1 t2

2

2 2 t2 2 2

1 W 120L iW 40 L i 1 1 1t t L i . 20 L i 802

2 2 4 2 W 30W W 20

L i ' L i 'W W ' 20 20 4. 20 W ' 5

t t 2 2

W W ' W ' 30 W ' 5 W ' 25


26/30

V. SNG NH SNGCu 58:(Chuyn H Vinh 2014 L1) Trong th nghim Y-ng giao thoa nh sng n sc vi Dkhngi, a c th thay i c. Ban u ti im M trn mn quan st l vn sng bc 6. Nu ln lt tng

hoc gim khong cchgia hai khe mt lng a th ti M l vn sng bc 3k hoc k; by ginu tng

khong cch gia hai khe thm mt lng a/3 (ngun S lun cch u hai khe) th ti M l vn sng bc

A. 9. B. 7. C. 8. D. 10.Hng dn :


Hng dn :

Cu 60:(Chuyn H Tnh 2014 - Ln 3)Trong th nghim Y-ng vgiao thoa nh sng, nh sng trngchiu vo khe S c bc sng t 415 nm n 760 nm. M l mt im trn mn giao thoa, c ng 3

bc xcho vn sng v mt trong ba bc x l bc x mu vng c bc sng 580 nm. M l vn

sng bc my ca bc xmu vng ni trn ?A. 5. B. 6. C. 3. D. 4.

Hng dn : Vtr 3 bc xcho vn sng, vn vng c bc l kv.

Ta c: 580v v vv vD k kD

x k ka a k k

. M 415 63 1,397v vk k k .

kv= 3: 2,3 k 4,2 => k = 3, 4 (khng tha mn).kv= 4: 3,1 k 5,6 => k = 4, 5 (khng tha mn).kv= 5: 3,8 k 6,99 => k = 4, 5, 6 (tha mn).kv= 6: 4,6 k 8,4 => k = 5, 6, 7, 8 (khng th a mn).



27/30

Hng dn : Chn B a L D

7, 63 %a L D

(Xem cng thc SGK bi thc hnh o bc sng nh sng bng hin tng giao thoa)


28/30

VI. LNG TNH SNGCu 62:(Chuyn H Vinh 2014 Ln 3) lectron trong nguyn tHidr chuyn tqu o dng cmc nng lng ln vqu o dng c mc nng lng nh hn th vn tc lectron tng ln 2,5 ln.

lectron chuyn tqu o

A. O vL. B. O vK. C.N vK. D.N vL.Hng dn :

2

00

kq2 2 2 2 at vmr2 0

2 2 0

2

5

vv q kq kqKhi electron chuyen ong tren quyao : m k v v

r mr nr m.n .rv

2,5 Chuyen tO Lv


Hng dn :


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VII. VT L HT NHNCu 64:(Chuyn H Vinh 2014 L3) K hiu c l vn tc nh sng trong chn khng. Mt ht vi m,c nng lng nghE0v c vn tc bng 12c/13 th theo thuyt tng i hp, nng lng ton phn ca

n bng

A. .12/E13 0 B. .E4,2 0 C. .E6,2 0 D. .13/E25 0

Hng dn : 0 0 0 021

E W E 1 E E 2,6Ev

1c

Cu 65:(Chuyn H Tnh 2014 - Ln 3)i vi nhng ht c tc ln, nu tnh ng nng theo c hcc in W= m0v

2/2 th sc sai s ng k. Nu mt ht c sai sni trn l 5% th ht c nng lng ton

phn gp bao nhiu ln nng lng ngh?

A. 1,035. B. 1,065. C. 1,084. D. 1,104.

Hng dn : ng nng tng i tnh: 20 2 21

11 /

K m cv c

. ng nng c in: 20

1W

2dm v .

* ng nng tng i tnh ng trong mi trng hp, ng nng c in c sai sl 5% tc ltnh chnh xc ca n l 95% so vi ng nng tng i tnh:

22 2

0 0 22 2

20 0

W 1 1 1 10,95% 0,95 1 0,95 1 0,0663

2 2 11 /

11,035

1

d vm v m c x xK cxv c

E m

E m x

.

Cu 66:(Chuyn H Tnh 2014 - Ln 3) Cho phn ng ht nhn .MeV8,23HeXD 4221 Nc trongthin nhin cha 0,003% khi lng ng v D21 (c trong nc nng D2O). Hi nu dng ton b teri

c trong 1 tn nuc thin nhin lm nhin liu cho phn ng trn th nng lng thu c l bao nhiu ?

Ly khi lng nguyn t teri l 2u.

A. 6,89.1013J. B. 1,72.1013J. C. 5,17.1013J. D. 3,44.1013J.

Hng dn :2 2

23 243030 2 . 2. .6,023.10 4,5.104D D D A

m g N n N .

Phn ng: 2 2 41 1 2 23,8 .D D He MeV Mi phn ng cn 2 ht nhn D.

Nng lng ta ra t1 tn nc: 24 13 131

W .4, 5.10 .23,8.1,6.10 1, 72.102

J .


Hng dn : Chn

2D p n

20p n

E m m m c 2, 2356 M eV

Gay ra phan ng hat nhan trenNL cua ti a can cung cap e

+ Cung cap cho hai hat san pham mot ong nang ban au

hf E W W f 6, 46.10 Hz


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