Ebook hướng dẫn giải chi tiết đề thi tuyển sinh đại học, cao đẳng môn vật lí phần 2

DE THI TUYEN SINH CAO DANG NAM

2010

M6n: VAT LI - Khoi A
Thdl gian lam bai: 90 phut
Cho biet: H S n g so Plang h = 6,625.10"^'*J.s, toe do a n n sang trong
chan k h o n g c = 3.10^m/s, do Idn dien t i c h nguyen to e = 1,6.10"^^C, so
Avogadro N A = 6,02.102^mor\V = 1,6.10~^^J.
Cdu 1: Cho p h a n uTng h a t n h a n | H + | H ^ ^,He+Qn + 17,6MeV.

Nang

li/cfng toa r a k h i t o n g hgrp duo'c 1 g k h i heU xap x i bang:
A. 5,03.10" J .

B. 4,24.10^ J .

C. 4,24.10^ J .

D. 4,24.10" J .

Gial
N
M o t m o l He c6 4g nen so nguyen tijf t r o n g I g He l a : N = ——.

4
Nang

\Mang

toa r a : E = N.17,6MeV = 6 , 0 2 . 1 0 ' ^ - .17,6.10^1,6.10"'^
4
= 42,38.10'° « 4,24.10" J .

Vay chgn dap an D.
Cdu 2: M o t m a c h dao dong dien tCf LC l i tiidng dang thiic h i e n dao
dong d i e n tii t U do. D i e n t i c h ciTc d a i t r e n m o t ban t u la 2.10'^C, ciro'ng
do dong d i e n ciTc d a i t r o n g mach la 0,1 TTA. Chu k i dao dong dien tif tif
do t r o n g m a c h b k n g :
A.

10'^
3

s.

B.

10"^
3

s.
^

C. 4.10-'s.

D. 4.10-'s.

Glai
N a n g li/grng m a c h dao dong:

2

2

1-

1

Chu k i dao dong: T = 27r>/LC = 2 ? : ^ = ^^"^"^^
1
0,l;r

= 4.10'(s).

Vay chgn dap an D.
Cdu 3: T a i m o t v i t r i t r o n g m o i trifdng t r u y e n a m , k h i cirdng do am
tang gap 10 Ian gia t r i ciXdng do a m ban dau t h i mu'c cu'dng do a m
D. g i a m di 10 d B .

C. t a n g t h e m 10 dB.

B. g i a m d i 10 B.

A. t a n g t h e m 10 B.

84

G i a i Chi ti6t de thi T S DH, C B Mon

Vat li

Giai
Mufc

CLfcfng

do a m ban dau: L, = lOlg —.

Mufc cufdng do a m k h i h = l O I i : L2 = 1 0 1 g ^ .
Ta c6: L ^ - L , = lOlg — - l O l g ^ - lOlg-^ = lOlglO = l O ( d B ) .

^0

^0

^1

Vay chgn dap an C.
Cdu 4: B a n dau ( t = 0) c6 m o t mau chat phong xa X nguyen chat. O
thdi diem t i mau chat phong xa X con l a i 2 0 % h a t n h a n chtfa b i p h a n
ra. D e n thcfi d i e m t2 = t i + 100 (s) so h a t n h a n X chtfa b i p h a n r a c h i
con 5% so v d i so h a t n h a n ban dau. Chu k i b a n r a ciia chat phong xa
do l a :
A. 25 s.

B. 200 s.

C. 50 s.

D . 400 s.

Giai
T a i thofi diem t i :

N„

ii

N

_ 20%No
OAO/.M _
0
N, = -_0f =
=—^=>2T
=5

(1)

T a i tho-i diem ts = t i + 100:

N„

1, + lUO

N

N2=-TTlW = 5 % N „ = - f ^ 2
2

'

=20

(2)

T
f'iil^.lil

Chia (2) cho (1) t a diXtfc: 2^ ^

,AA

= 4 - 2" => - ^ ^ = 2 «

T = 50(s).

Vay chon dap an C. .
Cdu 5: D u n g h a t p r o t o n c6 dong n a n g 1,6 M e V b a n vao h a t n h a n U t i
( j L i ) dufng yen. Gia suf sau p h a n ufng t h u dUgfc h a i h a t giong nhau c6
cung dong n a n g va k h o n g k e m theo t i a y. B i e t n a n g liiofng t o a r a cua
phan ufng l a 17,4 MeV. Dong n a n g ciia m 5 i h a t s i n h r a l a :
A. 15,8 MeV.

B. 19,0 MeV.

C. 7,9 MeV.

D . 9,5 MeV.

Giai
Trong triTcfng hcfp k h o n g k e m theo t i a y, theo d i n h luat bao toan
nang Itfdng, t o n g dong n a n g cua h a t s i n h r a p h a i bfing n a n g lifcfng cua
Giai Chi tiet de thi TS DH, CD Won Vat If

85


p h a n ufng t o a r a cpng vdri dong n a n g b a n dau. Theo do, neu goi K la
n a n g lufcfng cua m 6 i h a t t h i t a c6:
2 K = 17,4 M e V + 1,6 M e V = 19 M e V ^

K = 9,5 MeV.

Vdy chgn dap an D.
Cdu 6: M o t k h u n g day d i n phSng det h i n h chOr n h a t c6 500 vong day,
dien t i c h m o i v o n g l a 220 cm^. K h u n g quay deu v d i toe do 50 vong/giay
quanh m o t true doi xufng n a m t r o n g m a t p h i n g cua k h u n g day, trong
m o t tCr trtroTng deu c6 vectcf cam ufng tCf B vuong goc vdti true quay va
eo do Idfn — T . Suat d i e n dong cire d a i t r o n g k h u n g day bang:

571
A. 2 2 0 V 2 V .

B . 220 V .

C. I I O V 2 V .

D. I I O V .

Giai
Suat d i e n dong ciic d a i t r o n g k h u n g day b k n g :
f?
E g = coNOo = coNBS = 271.50.500.—.200.10-'= 2 2 0 ^ / 2 ( V ) .

571

Vdy chgn dap an A.
Cdu 7: M o t stfi day A B c6 chieu d a i 1 m cang ngang, dau A co dinh,
dau B gSn vdri m o t n h a n h cua a m thoa dao dong dieu hoa vdfi t a n so
20Hz. T r e n d a y A B eo m o t song dCrng o n d i n h vdri 4 bung song, B ducfc
eoi l a n u t song. Toe do t r u y e n song t r e n day l a :
A. 50 m/s.

• B. 2,5 cm/s.

C. 10 m/s.

D . 2 cm/s.

Giai
H a i dau A B dirde eoi l a n i i t song. Do vay t r e n day c6 4 m u i song.
Ta c6: I = 4-^2X=>X

=- =

0,5(m).

Toe do t r u y e n song: v = ^if = 0,5.20 = 10(m/s).

Vdy chgn dap an C.
Cdu

8: M o t nguon sang c h i p h a t r a a n h sang dcfn s^c eo t a n so

5.10^^Hz. Cong suat bufe xa dien tCf cua nguon l a l O W . So photon ma
nguon p h a t r a t r o n g m o t giay x a p x i hkng:
A. 0,33.10^^

B . 3,02.10^°.

C. 3,02.10^^

86

D . 3,24.10^^

Giai Chi tigt 66 thi TS DH, CD M6n V$t II


Giai
So photon m a nguon p h a t r a t r o n g m o t giay x a p x i bang:

N =— =
~
- r « 3,02.10'^
hf 6.625.1(r'-'.5.10'-'
Vay chgii dap an C.
Cdu 9: Theo thuyet luang tijf a n h sang, p h a t bieu nao dvidi day la sai?
A. P h a n tijf, ngiiyen tuf phat xa h a y h a p t h u a n h sang, cung c6

nghia la chung phat xa hay h a p t h u photon.
B. A n h sang diioc tao t h a n h bdi cac h a t goi l a p h o t o n .
C. N a n g iLfgtng ciia cac photon a n h sang l a nhtf nhau, k h o n g p h u
thuoc t a n so' ciia a n h »ang.
D . T r o n g chan k h o n g , cac photon bay doc theo t i a sang v d i toe do
c = 3.10^m/s.

Giai
N a n g lifcJng cua cAc photon s = h f n e n t a n so a n h sang khac nhau
thi nSng li/cfng e khac nhau.
Vay chgn dap an C.
Cdu 10: D a t dien ap u - Uocoscot c6 co thay doi dixac vao h a i dau doan
mach gom cuon cam t h u a n c6 do t\i cam L , di$n t r d t h u a n R va t u dien
CO dien dung C mSc n o i tiep. K h i co <

J — thi:
VLC

A. ciidng do dong dien t r o n g doan mach cung pha v d i dien a p giufa
hai dau doan mach.
B. dien ap hieu dung giufa h a i dau dien trcf t h u a n R n h o h o n dien
ap hieu dung giufa h a i dau doan mach.
C. cUdng do dong dien t r o n g doan mach tr§ pha so vdri d i e n ap giufa
hai dau doan mach.
D. dien ap hieu dung giffa h a i dau dien t r d t h u a n R b a n g d i e n ap
hieu dung giu:a h a i dau doan mach.

Giai
Khi

CO

<

t h i Z , - Zp > 0.

Khi

do Z = ^ R ' + ( Z ,

- Z , ) ' > R . Suy r a U R < U .

Vay chgn dap an B.
G\iii Chi ti^t de thi T S D H , C D Mon Vat li

87

.


Cdu 11: T r o n g scf do k h o i cua m o t may phat t h a n h dung song v6 tuyen
k h o n g C O bo p h a n nao diTdfi day?
D. Anten.

C. M a c h khuech d a i .

B. M a c h tach song.

A. M a c h b i e n dieu.

T r o n g scf do k h o i cua m o t m a y phdt t h a n h dung song v6 tuyen,
k h o n g can bo p h a n tach song.
Vdy chon dap an B.
Cdu 12: Song d i e n tCf
A. C O t h a n h p h a n dien tnfcfng va t h a n h phan tCf triTdng t a i mot diem
dao dong cung phi/cfng.
B. la d i e n tCr trLfomg Ian t r u y e n trong k h o n g gian.
C. l a song doc hoSc song ngang.
D . k h o n g t r u y e n dtfcfc t r o n g chan khong.
GiSi
Song d i e n tCr l a song ngang, t r u y e n diTcfc t r o n g chan k h o n g va k h i
t r u y e n t h l vectcf E va B luon vuong goc vdfi nhau.
Vdy chgn dap an B,
Cdu 13: M a c h dao dong l i t i i d n g gom cuon cam t h u a n c6 do i\S cam L
va tu d i e n c6 d i e n dung C dang thifc h i e n dao dong dien tCf tiT do. Goi
Uo l a d i e n ap ciic d a i giufa h a i ban t u ; u va i la dien ap giufa h a i ban t u
va ciTcfng dp dong d i e n t r o n g mach t a i thofi diein t . He thufc d u n g l a :

D. i ^ = ^ ( U ^ u ^ ) .

C.i^=LC(U^u^).

B. i ^ = ^ { U ^ u - \ ) .

A. i ^ = V L C ( u ^ - u = ) .

Giai
A p dung d i n h l u a t bao t o a n n a n g liTong cho mach L C , t a c6:
-CU^ =-CU^+lLi^ o i ^ =-(u^-ir).
Vdy chgn dap an B.

Cdu 14: M o t v a t dao dong dieu hoa v(5fi bien do 6 cm. Moc the nSng d
v i t r i can b^ng. K h i v a t c6 dong nkng b k n g ^ I a n ccf n a n g t h i v a t each
v i t r i can bSng m o t d o a r .
A. 4,5 cm.

B. 6 cm.

C. 4 cm.

D. 3 cm.
Giai chi tiet cJe thi T S OH, C D M6n VSt 1(

88


Gial
K h i dong n a n g bSng — ccf n a n g t h i the n a n g bang:
4
Wt = W - Wd = W - - W = - W .
4
4
K h i do t a c6: - k x " = - . - k A " <=> x = — <=> x = — = 3 ( c m ) .
2

4 2

4

2

^ ^

. Vay chgn dap an D.
Cdu 15: Dat dien ap xoay chieu u =
CO

dien

UQCOS

cot vao h a i dau doan mach chi

t r d thuan. Goi U la dien ap hieu dung giOfa h a i dau doan mach;

i, lo yk I Ian liJc/t l a gia t r i tilc t h d i , gia t r i
cua

CLTcfng

dai va gia t r i hieu dung

do dong dien t r o n g doan mach. He thufc nao sau day

A. - ^ - 1 = 0.
Uo

C L T C

sai?

B.-^-i.O.

lo

U

C. — + — = 1.

D.

1

+— = yjl.

Giai
Tac6:

. _ ^ . Jo_
V2U0
V2I0
^0
^^'0

U„
u

i _ uV2coscot

ij~T~
U

Uo

1
V2

l>^coscot

u

I •

1

1

1

lo

V2

72

1 . 0.
V2
= 0.

• + — = —p= + -

Vdy chqn dap an C.

Cdu 16: T r o n g cac loai t i a : Rcfn-ghen, h o n g ngoai, tuf ngoai, dofn sac
mau luc; t i a c6 t a n so nho n h a t l a :
A. t i a h o n g ngoai.

' B. t i a Rcfn-ghen;

C. t i a dofn sAc mau luc.

D. t i a tuf ngoai.

Giai
T i a h o n g ngoai c6 bifdc song I d n n h a t nen c6 t a n so nho n h a t .
Vay chgn dap an A.
Cdu 17: D ^ t dien ap xoay chieu vao h a i dau doan mach gorh d i e n t r d
thuan 4 0 Q va t u dien mic n o i tiep. B i e t dien ap giufa ha^.dau doan
Giai Chi tiet tie thi T S B H , C D Mon Vat li

89


mach lech pha y so vdi cifcfng do dong dien trong doan mach. Dung
khang ciia tu dien bkng:
A. 40V3Q.

B. 20V3Q.

C. 40Q.

Giai
Do lech pha: tancp =

R

Zc
= tan-o ^
= V3 « Z"^ = R V 3 = 40V3 ( Q ) .
3
R

Yay chon dap an A.

•

'

Cdu 18: Hieu dien the giufa hai dien cifc cua ong Cu-lit-gitf (ong tia X)
la UAK = 2.10^V, bo qua dong nang ban dau cua electron k h i buft ra
khoi catot. Tan so Idn nhat cua tia X ma ong c6 the phat ra xap xi
bang:
D. 4,83.10'^ Hz.

C. 4,83.10'^ Hz.

B. 4,83.10^' Hz.

A. 4,83.10^^ Hz.

Giai
Ta c6: eU = hf =^ f -

6,625.10-'-'

h

1,6.10-".2.10'

eU

= 4,83.10".

Vay chon dap an C.
Cdu 19: Mot song ccf truyen trong mot moi tri/dng doc theo true Ox vdi
phirctog t r i n h u = .Scos(67rt-7rx) (cm) (x tinh bSng met, t tinh hkng
giay). Toe do truyen song bang:
A. 3 m/s.

D. i m/s.
3

C. - m/s.
6

B. 6 m/s.

GiSi
So sanh phi/orng t r i n h song u = 5cos(6;rt-7tx) vdri phiTorng trinh
tong quat u = UQ COS cot

(0

ta thay: co = 671; — = 7i.

X

V

Taco: v = - = — = 6(m/s).
71

71

Vay chon dap an B.
Cdu 20: Trong so cae hanh tinh sau day cua he Mat Trori: Thuy tinh,
Trai Dat, Tho t i n h , Moc t i n h ; hanh tinh xa Mat Trcfi nhat la
A. Moc t i n h .

B. Thuy tinh.

C. Tho tinh.

D. Trai Dat.

Giai Chi tiet d e thi T S D H , CO M 6 n V | t l(

90


Giai
Trong so cac h a n h t i n h t h i Tho t i n h xa M a t Tro'i n h a t .
Vay chgn dap an C.
Cdu 21: K h i n o i ve song am, phat bieu nao sau day la s a i ?

A. Song a m t r o n g k h o n g k h i la song ngang.
B. Song a m t r u y e n dxiac t r o n g cac m o i trUdng rAn, l o n g va k h i .
C. Song a m t r o n g k h o n g k h i l a song doc.
Cling m o t n h i e t do, toe do t r u y e n s o n g a m t r o n g k h o n g

D. d

khi

nho han toe do t r u y e n s o n g a m trong nUdc.

Giai
Song a m t r o n g k h o n g k h i la song doc n e n p h a t bieu A sai.
Vay chgn dap an A.
Cdu 22: N g u y e n tijf h i d r o chuyen ttf t r a n g t h a i dUng c6 n a n g l u g n g
En = - l , 5 e V sang t r a n g t h a i dCfng c6 nSng l i i o n g E m = -3,4eV. Budtc
song cua bufe xa ma nguyen tiu h i d r o p h a t r a xap x i b k n g :
A. 0,654.10-^ m.

B. 0,654.10-^ m .

C. 0,654.10"^ m .

D. 0,654.10"^ m .

Giai
Taco:—= E2-E,
^ , . ^ . _ ^ 6 2 5 . 1 0 - 3 . 1 0 E^-E,

3^^^.

(1,5 + 3,4)1,6.10""

Vay chgn dap an B.
Cdu 23: M o t con iSc 16 xo gom v i e n b i nho va 16 xo nhe c6 do cufng
lOON/m, dao dong dieu h6a vdfi b i e n do 0,1 m . Mo'c the n a n g d v i t r i
can bang. K h i v i e n b i each v i t r i can bSng 6 cm t h i dong n a n g cua eon
l^c bang:
A. 0,64 J .

B. 0,32 J .

C. 3,2 m j .

D. 6,4 m J .

Giai
Ccf n a n g cua con l^c: W = ^ k A ^
The nSng cua con lac k h i each v i t r i can h^ng

6cm:

W=-k.6.10-'.
' 2
Giai Chi ti^t 66 thi T S B H , C D Mon Vat If

91


Dong n a n g cua con lac k h i do:

Wd = W - Wt = - 1 0 0 ( 1 0 - ' ) ' - { 6 . 1 0 - ' ) '
2

= 0.32J.

Vay chgn dap an B.
Cdu 24: DSt d i e n ap u = 2 2 0 V 2 c o s l 0 0 7 t t (V) vao h a i dau doan mach
A B g o m ' h a i d o a n m a c h A M va M B mSc n o i t i e p . D o a n A M

gom

d i e n tror t h u a n R mSc n o i t i e p vdfi cuon cam t h u a n L, doan M B chi
CO t u d i e n C. B i e t d i e n ap giufa h a i dau doan m a c h A M va d i e n ap
giufa h a i dau d o a n m a c h M B c6 gia t r i hieu d u n g b ^ n g nhau nhUng
lech pha nhau — . Dien ap hieu dung giCfa hai dau doan mach A M bkng:
A. 110 V.
C. 220 V2

V.

B

220

s

V.

AM

D. 220 V.
Giai

Diia vao de b a i , t a c6 g i a n do vector nhtf
h i n h ve. Diia vao g i a n do vector t a c6 the t h a y
UAM = UAB = U C

= 220 (V).

Vay chqn dap an D.
Cdu 25: K h i m o t v a t dao dong dieu hoa t h i
A. liJc keo ve tac dung len vat c6 do Idn ciic dai k h i vat 6 vi t r i can bkng.
B. v a n toe cua v a t c6 do Idn ciSc dai k h i v a t of v i t r i can bkng.
C. gia toe cua v a t c6 do Idfn c\Xc dai k h i v a t d v i t r i can bang.
D. liic keo ve tac dung len vat c6 do Idn t i le vdri b i n h phiidng bien do.
Giai
K h i m o t v a t dao dong dieu hoa t h i v a n toe cua v a t c6 do Idn cxlc
dai k h i v a t d v i t r i can bang.
Vay chon dap an B.
Cdu 26: M o t l a n g k i n h t h u y t i n h c6 goc chiet quang A = 4°, dat trong
k h o n g k h i . C h i e t suat cua l a n g k i n h doi v d i a n h sang do va t i m Ian
lUgrt 1^ 1,643 va 1,685. Chieu mot chijm t i a sang song song, hep gom
hai bufc xa do va t i m vao m a t ben eua l a n g k i n h theo phiicfng vuong
goc v d i m a t nay. Goc tao bdi t i a do va t i a t i m sau k h i 16 r a k h o i mat
ben k i a ciaa l a n g k i n h xap x i bang:
A. 0,336°.

B. 1,416°.

C. 13,312°.

92

D. 0,168°.

Giai Chi ti6't de thi TS DH. CD M6n Vat li


Giai
Goc l e c h cua t i a s a n g d o : D i = A(nd - 1) = 4 ( 1 , 6 4 3 - 1) = 2,572°.
Goc l e c h cua t i a s a n g t i m : Dg = A(nt - 1) = 4 ( 1 , 6 8 5 - 1) = 2,74°.
Goc l e c h giffa h a i t i a : A D = Dz - D i = 2,74 - 2 , 5 7 2 = 0,168°.
Vay chgn

dap an D.

Cau 27: T a i m o t n o i t r e n m a t d a t , con l a c dofn c6 c h i e u d a i C d a n g dao
dong d i e u h o a v d i c h u k i 2s. K h i t a n g c h i e u d a i c u a c o n iSc t h e m 2 1 c m
t h i c h u k i dao d o n g d i e u h o a cua n o l a 2,2s. C h i e u d a i t b a n g :
A . 2,5 m .

B. 2 m.

C. 1 m .

D . 1,5 m .

Giai
B a n d a u , c h u k i dao d o n g c u a c o n l&c l a :
T, =271 -

= 2(s)

(1)

Sau k h i t a n g t h e m 2 1 c m , c h u k i dao d o n g c u a c o n ISc l a :

T,=2.Alil=2.2(s)

(2)

TCr (1) v a (2) t a c6:
= 1.1- = 1 , 2 1 <::><: + 21 = l , 2 K « f

= 100(cm).

g
Vdy chgn

dap an C.

,

Cdu 28: D a t d i e n a p u =

coscot v a o h a i d a u c u o n c a m t h u ^ n c6 do t t f

cam L . T a i t h d i d i e m d i e n a p giOra h a i d a u c u o n c a m c6 do Idfn cifc d a i
thi

CLfdng

do d o n g d i e n q u a c u o n c a m b a n g :

A . 0.

B.

c.

ii,

coL

2coL

D.
V2COL'

Gi^i
Cucfng do d o n g d i e n c h a y q u a c u o n c a m : i = IQ COS cot

K h i u = UoCoscot = Uo t h i coscot = 1 . K h i do
Vay chgn

cos cot

—
2
n

—
2

= 0.

dap an A.

Giai Chi tiet a6 thi TS DH, CD IVIon Vat li

"

93


Cdu 29: M o t m a y p h a t dien xoay chieu m o t pha c6 p h a n cam la roto
quay vdri toe do 375 vong/phut. T a n so ciia suat dien dong cam ufng ma
m a y p h a t tao r a la 50 Hz. So cap cifc cua roto b k n g :
A. 16.

B. 8.

C. 4.

D. 12.

Giai
Ta c6: 375 vong/phut = 6,25 vong/giay.
T a n so dong d i e n p h a t r a l a : f = p.n => p = — =
= 8.
n

6.25
Vay chgn dap an B.
Cdu 30: H i e n tiTofng nao sau day k h a n g d i n h a n h s a n g c6 t i n h chat song?

A. H i e n tMng quang d i e n t r o n g .
B. H i e n tiiofng quang dien ngoai.
C. H i e n ti/o'ng quang p h a t quang.
D. H i e n tiTdng giao thoa a n h s a n g .

Giai
Hien tiiong giao thoa anh sang khang dinh anh sang c6 t i n h chat song.
Vay chgn dap an D.
Cdu

31: C h u y e n d o n g ciia m o t v a t la t o n g ho'p cua h a i dao

dong

dieu hoa cung phuo'ng. H a i dao dong nay c6 phiTo'ng t r i n h I a n lugrt la
X, = 3coslOt(cm)

va x , = 4 s i n

1,

(cm). Gia toe ciia v a t c6 do Idn

ciic dai b a n g :
A. 1 m / s l

B. 5 m / s l

C. 7 m/s^

D. 0,7 m / s l

Giai
Ta c6: x , = 4sin ' l O t + ^ ' = 4 c o s l 0 t ( c m ) .
2
H a i dao dong x i , X 2 cung pha nen dao dong t d n g hdp c6 bien do:
A = A i + A2 = 7 (cm).
Gia toe ciia v a t : a = x " = - C O " A cos (cot+ 9 ) .
Do Idrn cifc d a i cua gia toe: a,„^^ = co"A = 10".0,07 = 7 ( m / s " ) .
Ydy chgn dap an C.
94

Giai Chi tigt de thi T S OH, C D M6n V§t li


Cdu 32: Treo con \kc do'n vao t r a n m o t oto t a i noi c6 gia toe t r o n g
trUdng g = 9,8 m/s^. K h i oto dufhg yen t h i chu k i dao dong dieu hoa cua
con lac la 2s. Neu oto chuyen dong t h i n g n h a n h dan deu t r e n diTcfng n&m
ngang v d i gia toe t h i chu k i dao dong dieu hoa cua con iSe xap x i bang:
A. 1,98 s.

B . 2,00 s.

C. 1,82 s.

D. 2,02 s.

Giai
Gia toe bieu k i e n ciia con lac:
g, = 7 g - V a - = V l 0 - + 2 - = 1 0 , 0 4 ( m / s - ) .
Chu k i dao dong:

X
T

V

l i ^ T = To^«l,98(s).

Vdy chon dap an A.
Cdu 33: Chleu a n h sang t r S n g do mot nguon n o n g sang p h a t r a vao
khe hep F cua m o t may quang pho l a n g k i n h t h i t r e n t a m k i n h a n h
(hoac t a m k i n h mcj) ciia buong a n h se t h u diroc:
A. a n h sang trSng.
B. bay vach sang tCf do den t i m , ngan each nhau hang nhOfng
khoang t o i .
C. eac vach mau sang, t o i xen ke nhau.
D. m o t dai c6 mau tCr do den t i m n o i l i e n nhau m o t each l i e n tuc.
Giai
T r e n t a m k i n h a n h (hoac t a m k i n h mo') ciia buong a n h se t h u diio'e
quang pho ciia a n h sang t r S n g gom m o t dai mau tCf do den t i m .
Vdy chon dap an D.
Cdu 34: K h i n o i ve t i a a p h a t bieu nao sau day la s a i ? ,
A. T i a a la dong cac h a t n h a n h e l i (^He).
B. IChi d i t r o n g k h o n g k h i , t i a a l a m ion hoa k h o n g k h i va m a t
dan nang lUcfng.

C. K h i d i qua d i e n trUcfng giijfa h a i b a n t u d i e n , t i a a b i lech ve
phia ban a m cua t u d i e n .
D. T i a a phong r a tCr h a t n h a n v6'\e do bang 2000 m/s.
Giai
Tia a phong r a tCr h a t n h a n vdfi toe do b k n g k h o a n g 2.10'm/s.
Vdy chon dap an D.
Giai Chi tiet de thi TS DH, CD M6n Vat If

95


Cdu 35: K h i n o i ve t i a h o n g ngoai, p h a t bieu nao dufdri day la sai?
A. Tac dung n o i b a t n h a t cua t i a hong ngoai la tac dung nhiet.
B. T i a h o n g ngoai c6 t a n so Idn hofn t a n so cua a n h sang do.
C. Tia hong ngoai cung c6 the bien dieu difoc nhiT song dien tii cao tan.
D. T i a h o n g ngoai c6 k h a n a n g gay r a m o t so p h a n ufng hoa hoc.

Giai
T i a h o n g ngoai c6 biidrc song d a i hcfn a n h sang do v i the t a n so cua
no phai nho ho'n t a n so cua a n h sang do.
Vay chon dap an B.
Cdu 36: M o t v a t dao dong dieu hoa vdri chu k i T. C h o n goc t h d i gian
la liic v a t qua v i t r i can bSng, v a n toe ciia v a t b a n g 0 I a n dau t i e n or
thcfi d i e m :
A.

I.
4

B.

I.

C.

6

T
8

a I.
2

Giai
Chon goc thofi gian Itic v a t d v i t r i can b l n g . Ta c6:
+ Phi/tfng t r i n h dao dong: x = A cos (ot —
2)
+ Phi/Ong t r i n h v a n toe: v = -coA sin cot —
2)
Khi

V

0 t h i sin
sin cot-—
2)
V
2n
— t
T

=

n

—2 =

2n^
n
T
— t = - < = > t = —.
T
2
4

Vay chon dap an A.
Cdu 37: D a t d i e n ap u = 200cosl007ct (V) vao h a i dau doan mach gom
m o t b i e n t r d R m^c n o i t i e p v d i m o t cuon cam t h u a n c6 do t i f cam
— H . Dieu c h i n h b i e n tror de cong suat toa n h i e t t r e n b i e n t r d dat cUc
7t

,

•

•

d a i , k h i do ctfcfng do dong d i e n hieu dung t r o n g doan mach bSng:
A. 2 A.

B. 1 A . ^

C.

- t

96

D. V2 A.

A.

Giai Chi tiet <36 thi TS OH, CD M6n V4t I


Giai
2r.

Cong suat cua b i e n tror l a : P = I^R =

U=

U-R

R
Theo bat dang thu'c Cosi, cong suat dat gia t r i

CLTC

dai k h i :

R = Z L = coL = 100<:i
CuoTng do dong d i e n hieu dung t r o n g doan mach:
, ^ U ^
Z

2 0 0 _ - ^
^/2.VlOQ=+100=

Vay chqn dap an B.
Cdu 38: T r o n g t h i n g h i e m Y-ang ve giao thoa a n h sang, cac khe hep
dLfgfc

chieu sang hdi anh sang dcfn sac. Khoang v a n t r e n m a n la 1,2mm.

Trong khoang giOfa h a i d i e m M va N t r e n m a n or cung m o t p h i a so v d i
van sang t r u n g t a m , each v a n t r u n g t a m I a n Itfgft 2 m m va 4 , 5 m m , quan
sat di/cfc:
A. 2 v a n sang va 3 v a n t o i .

B. 2 v a n sang va 1 v a n t o i .

C. 3 v a n sang va 2 v a n t o i .

D . 2 v a n sang va 2 v a n t o i .

Giai
T a c o : Ad = 4 , 5 - 2 = 2 , 5 ( m m ) .
So khoang v a n : n =

2 5
1,2

« 2 v a n (n nguyen).

Vay ta chi quan sat dticfc 2 v a n sang (each v a n t r u n g t a m 2,4mm
va 3,6mm) va 2 v a n t o i (each v a n t r u n g t a m 3 m m va 4,2mm).
Vay chgn dap an D.
Cdu 39: M o t dong ccf k h o n g dong bo ba pha mac theo k i e u h i n h r.ao
dUcfc noi vao mach dien ba pha c6 dien ap pha Upha = 220V. Cong suat
dien cua dong cof la 6,6 V3 k W ; he so cong suat cua dong ccf ia

.

Cif&ng do dong di$n hieu dung qua m 6 i cuon day cua dong ccf bang:
A. 20 A .

B. 35 A .

C. 60 A .

D . 105 A .

Giai
Ta c6: P = 3.Pi = S.UIeoscp =^ I =

3Ucos(p

= 6,6.73.10^.2 ^
3.220.V3

Vay chgn dap an A.
QAi chi tiet de thi TS DH, CD Mon Vat If

97


Cdu 40: So vdi h a t n h a n ^^Si, h a t n h a n ^Ca

c6 nhieu hofn:

D . 6 n o t r o n va 5 proton.

C. 5 ncftron va 12 p r o t o n .

B. 5 n o t r o n va 6 p r o t o n .

A . 11 ncftron va 6 p r o t o n .

Giai
H a t n h a n " S i c6 14 p r o t o n , 15 ncftron.
H a t n h a n 20
Vdy chgn dap
Cdu

41:

c6 20 p r o t o n , 20 ncftron.
an

B.

D a t d i e n ap u =

UoCOS

cot + — ( V )
6

vao hai dau doan mach

gom d i e n trof t h u a n R va cuon cam t h u a n c6 do t i i cam L mac noi tiep
t h i dicing do dong dien qua doan mach la i =

sin cot + 12

( A ) . T i so

giiJa dien t r d t h u a n R va cam k h a n g cua cuon cam la:
C. 1.

B. V3.

A. 1.

D.

2

Giai

Ta c6: u =

'
71
2n
cos cot + — = UQ sin cot + — + — = UQ sin cot + 6
2
V
6
3 )

Do lech pha giC?a dien ap va ctfcfng do dong dien:
_

271

571

_

71

^ ~ T ~ T 2 ~ 4 '
Ta c6: ^ = t a n - = l .
R
4
Vdy chgn dap

an A.

Cdu 42: D a t d i e n ap u =

cos cot vao h a i dau doan mach gom dien tror

t h u a n R va t u d i e n C mAc n o i t i e p . Biet dien ap giua hai dau dien t r d
t h u a n va d i e n ap giCa h a i ban t u dien c6 gia t r i hieu dung bang nhau.
P h a t bieu nao sau day la sai?
A. CiTorng do dong d i e n qua doan mach tre pha

so v d i dien ap

giiJa h a i dau doan mach.
98

Giai Chi tietde thi T S D H . C D Mon Vatii

?


B. D i e n ap giuTa h a i dau d i e n trof t h u a n sdm pha — so v d i dien ap
4
giOfa h a i dau doan mach.
C. CiTcfng do dong dien qua doan mach scJm pha — so v d i dien ap
4
giOfa h a i dau doan mach.
D. D i e n ap giufa h a i dau t u dien t r e pha — so v d i d i e n ap giuTa h a i
4
dau doan mach.
Giai

Phat bieu sai: "CiTdng do dong dien qua doan mach t r i pha — so
•
•
4
vdfi dien ap giufa h a i dau doan mach".
Vay chon dap an A.
Cdu 43: T r o n g cac h a t scr cap: pozitron, p r o t o n , p h o t o n , n p t r o n ; h a t c6
khoi liJcfng n g h i bang 0 l a :
A. pozitron.

B. p r o t o n .

C. ncftron.

D. photon.

Giai

Photon la h a t scf cap c6 k h o i Itfcfng n g h i bang 0.
Vay chgn dap an D.
Cdu 44: P h a n ufng n h i e t hach la
A. phan ufng trong do mot hat nhan nang v9 t h a n h 2 m a n h nhe hom.
B. p h a n ufng h a t n h a n t h u n a n g liTgrng.
C. S L T k e t hcfp h a i h a t n h a n c6 so k h o i t r u n g b i n h tao t h a n h h a t
nhan nang hon.
D. p h a n ufng h a t n h a n toa n a n g lUcfng.
Giai

Phan ufng n h i e t hach la p h a n ufng h a t n h a n toa n a n g lucfng.
Vay chgn dap an D.

Cdu 45: M a c h dao dong l i tudng gom cuon cam t h u a n c6 do t i f cam L
khong doi va t u dien c6 dien dung C t h a y doi dtfofc. K h i C = C i t h i t a n
so dao dong r i e n g cua mach b k n g 30 k H z va k h i C = C2 t h i t a n so dao
Giai Chi tiet de thi TS DH, CD M6n Vat li

-

99


c c
d o n g r i e n g cua m a c h b a n g 40 k H z . N e u C = —

t

h

i

t a n so dao

d o n g r i e n g cua m a c h b a n g :
A . 10 k H z .

B.'*IO

kHz.

C. 2 4 k H z .

D

50 k H z .

Giai

=

K h i C = Ca t h i

f, =

Khi C = Ci thi

1

<=> f, = •

1

47t'LC,

1

1

n''

27r7Lq « f; = 4 7 i ' L C , •

1

1

1

4n~L
(vdi C =

Suy r a :

1

2 y

C.+C, _
C,C

~ 4n'L'

47r'LC

C,C
1^2

f,' + f^' = f ' =i> f = yjf^+f^

=

V30-+40- = 5 0 ( k z ) .

V g y c / i o n d d p an D.
Cdu

46: O m a t t h o a n g cua m o t c h a t l o n g c6 h a i n g u o n k e t h o p A v a B

dao d o n g d i e u h o a c u n g p h a v d i n h a u v a t h e o phiTdng t h a n g dufng. B i e t
t o e do t r u y e n s o n g k h o n g d o i t r o n g q u a t r i n h I a n t r u y e n , biTdfc s o n g do
moi

n g u o n t r e n p h a t r a b a n g 12 c m . K h o a n g e a c h n g a n n h a t giufa h a i

d i e m d a o d o n g v 6 i b i e n do
A. 6 cm.

CLTC

d a i n a m t r e n doan t h a n g A B l a :

B . 12 e m .

C. 3 c m .

D . 9 em.

Giai
K h o a n g e a c h giufa h a i d i e m dao d o n g v d i b i e n do ciTe d a i nkm t r e n
1
X
\2

d o a n t h a n g A B l u o n b k n g — biTdc s o n g n e n M - — = — = 6 ( c m ) .
Vdy
Cdu

chon

dap an A.

47: 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 a n h s a n g , h a i k h e di/gfc

c h i e u s a n g d o n g t h c f i b d i h.ai bufc x a d d n sac c6 budc s o n g I a n liTcft l a
A, 1 v a ^ 2 - T r e n m a n q u a n s a t c6 v a n s a n g b a e 12 c u a X i t r u n g v o i v a n
s a n g b a c 10 c u a > . 2 - T i so —

A.

2.

B.

3

bSng:

I6

C.

1.

D.

100

I.

Gi4i Chi ti^t 0% thi TS DH. CD Mon Vat If


Giai
T a i v i t r i 2 v a n sang t r u n g nhau, ta c6:
\2X, =10?i, = > ^

= -.

Vdy chgn dap an B.

,

Cdu 48: M o t con iSc 16 xo dao dong dieu hoa v d i t a n so 2 f i . D o n g nang
cua con iSc bien t h i e n t u a n hoan theo t h 6 i gian vdri t a n so' £2 b k n g :
A.i.
2

B.fi.

C. 4 f i .

D. 2fi.

GiSi
V i chu k i cua dong nang b k n g m o t nufa chu k i cua dao dong n e n
t a n so dong n a n g gap 2 Ian t a n so dao dong: fa = 2fo = 4 f i .
Vdy chgn dap an C.
Cdu

49:

Mot

con

iSc

16 xo gom

vat

nho

va

16 xo nhe

c6

do

cufng

lOON/m. Con l^c dao dong dieu h6a theo phifofng ngang v d i phiTcfng
t r i n h x = Acos((ot + (p) . Moc the nkng t a i v i t r i can bang. K h o a n g t h 6 i
gian giufa hai I a n l i e n t i e p con l&c c6 dong n a n g b a n g the nSng la 0,1s.
Lay 71^ =10.

Kho'i Itfgfng v a t nho bang:

A. 400 g.

B. 100 g.

C. 200 g.

D . 40 g.

T r o n g m o t chu k i dao dong, c6 4 I a n dong nSng b a n g the nSng nen
t a c o : T = 4At = 4.0,1 = 0 , 4 ( s ) .
m
cong thufc T = 2n — suy r a :
k

T\

m =-

4TI^

4.10

= 0,4(kg) = 400(g).

Vdy chgn dap an A.
Cdu 50: M o t chat c6 k h a n a n g p h d t ra a n h sdng p h a t quang vdfi birdrc
s6ng0,55^m. K h i dung a n h sang c6 birdc song nao dudi day de k i c h
thich t h i chat nay k h o n g the p h a t quang?
A. 0,45 ^ m .
G\k\i tiSt

B. 0,35 j ^ m .

thi TS DH, CD M6n V^t If

C. 0,50 ^ m .

D . 0,60 ^ i m .
101


Giai
Theo d i n h l u a t Xtoc, a n h sang k i c h t h i c h p h a i c6 h'Jdc song nho
hcfn hiXdc song a n h sang p h a t quang. Trong cac hiidc song t r e n t h i hu6c
song CO g i a t r i 0,60 p. m k h o n g the phat quang.
Vqy chon dap an D.
Cdu 51: P o l o n i ^^Po phong xa a va b i e n d d i t h a n h c h i Pb. Biet k h o i
lUcfng cac h a t n h a n Po; u ; Pb I a n \\iat l a : 209,937303u; 4,001506u;
MeV
205,929442u v a l u = 931,5 — — . N a n g liTcfng t o a r a k h i m o t h a t n h a n
c
poloni p h a n r a x a p x i bang:

D. 2,96 MeV.

C. 5,92 M e V .

B . 29,60 MeV.

A . 59,20 M e V .

Giai
Do h u t k h o i : Am = mp^ - (n^Pb +

)

= 209,937303U - 205,929442u -4,001506u = 0,006355u.
AE = A m . c ' = 5 , 9 1 9 6 8 2 5 « 5,92 MeV.
Vay chgn dap an C.
Cdu 52: M p t scfi d a y chieu d a i i cSng ngang, h a i dau co d i n h . T r e n
day dang c6 song d t o g v o i n b u n g song, toe do t r u y e n song t r e n day
la v. K h o a n g t h d i g i a n giuTa h a i I a n l i e n tiep scfi day duoi t h a n g l a :
A. ^ .
n£

B.

5^.

C. ^ .
2nv

£

D.

'
nv

GiSi
Ydi

I l a hudc song t h i - = - = > > . = — .
2
n
n

\
Chu k i dao dong: T = - = — .
V
nv
K h o a n g thcfi gian giufa h a i I a n l i e n t i e p scri day du6i t h i n g l a :
2

nv

•

Vay chgn dap an D.
102

Giiichitigt

Cdu 53: K h i v a t r a n quay b i e n doi deu quanh m o t true co d i n h t h i
A. gia toe goe eua v a t k h o n g doi.
B. tdng roomen eua eae ngoai life tac dung l e n v a t doi vdti true nay
bang khong.
C. gia toe toan p h a n eua m o t d i e m t r e n v a t luon k h o n g doi.
D. toe do goe eua v a t k h o n g doi.

Giai
K h i v a t ran quay b i e n doi deu quanh m o t true eo d i n h t h i gia toe
goe eua v a t k h o n g doi.
Vay choii dap an A.
Cdu 54: Trong eac nguon bufe xa dang hoat dong: ho quang d i e n , m a n
hinh may v6 t u y e n , 16 siTofi dien, 16 v i song; nguon p h a t r a t i a tuf ngoai
manh n h a t la
A. ho quang dien.

B. 16 v i song.

C. m a n h i n h m a y v6 t u y e n .

D. 16 sirdi d i e n .

Giai
V a t or n h i e t do eao hcfn se p h a t r a n h i e u t i a tuf ngoai hcfn. T r o n g
cac nguon bufe xa t r e n t h i ho quang dien d n h i e t do eao n h a t .
Vay chgn dap an A.
Cdu 55: M o t b a n h xe dang quay quanh m o t true eo d i n h v10 rad/s t h i h i h a m . B a n h xe quay eham dan deu, sau 5 s ke tCf liic
ham t h i dCfng h i n . Gia toe goe eua b a n h xe eo do I d n l a :

A. 2 r a d / s l

B. 0 , 2 r a d / s l

C. 5 0 r a d / s l

D. 0,5rad/sl

Gi^i
Gia toe goe: y = -^

=

= - 2 rad/s^.

V i xet ve do Idrn n e n t a ehon gia t r i 2 rad/s^.
Vay chgn dap an A.
Cdu 56: D a t dien ap u = uV2coscot (V) vao h a i dau doan mach

gom

cuon earn t h u a n mae n o i tie'p vdri m o t b i e n t r d R. l?ng v d i h a i giA t r i
Ri = 20 Q va R2 = 80 Q eua b i e n t r d t h i cong suat t i e u t h u t r o n g
doan maeh deu bang 400 W. Gia t r i eua U l a :
A. 400 V .

B. 200 V .

Giii Chi l\6t 06 thi TS DH, CD M6n V$t li

C. 100 V2 V .

D . 100 V .
1 03


Giai

K h i cong suat tieu thu trong doan mach hang nhau, ta c6:
z

20^+Zl
20

r - =-.

O

8 0 + Z'L
80

20'+Zl
.
1

SO + Zl
4

« 2 0 ' . 4 + 4 Z ' ^ = 8 0 + Z'L « 3 Z [ •= 4 8 0 0

^

Taco:

P(Rf+zM

U ' - - ^ ^ ^

R,

^

=

ZL =

40(Q).

400(400 + 1600)
^ = 40000 =^ U =

20

,

,

200(V).

^ ^

Vay chgn dap an B.
Cdu 57: Mot vat dao dpng dieu hoa doc theo true Ox. Moc the nang d
vi tri Cfin bkng. CJ thcfi diem do Idfn van toe cua vat bang 5 0 % van toe
cifc dai thi ti so giufa dong nang va ccf nang cua vat la:
A.!.
2

B.'i.

C . l .

4

D.l.
3

4

Giai
Goi

V 1^ v a n

toe

cua

vSt,

K h i V = 50%vo = ^ ,
2

VQ la

van

toe

CLTC

dai.

taco:

+ Ca nang cua vat: W = mv^ =
,

.

+ Dong nang cua vat:

, , r

mvl mvl
=^
=

=—

W

«

mv^

1

2

Ti so giufa dong nang va ccf nang: — - = — ^ =
-.
r- = - .
W
mvp
^
mvo
4
.
~2~
•

Vdy chgn dap an B.
Cdu 58: V a t r ^ n quay quaiih mot true eo dinh A . Goi Wa, I va L Ian
luat la dong nang quay, momen qudn tinh va momen dong lUcfng cua
vat doi vdi true A . Moi lien he giO:a Wa, I va L la:
A. W, = — .
B. Wd = 21.V.
C . W, = — .
104

'

D. W, =

Giaichitigtd^thiTSOH, CDM6nV4tl(


Giai

Dong

nang quay:

Momen dong
Suy

Wa = — I©'.

liTdng:

L = Ico ^

= I^co\

Wd = — .
21'
Vdy chon dap an C.
Cdu 59: Mot dong ho chuyen dong t h i n g deu v6i toe do v = 0,8c (vdfi e
la toe do anh sang trong chan khong). Sau 12 phut (tinh theo dong ho

do), dong ho nay chay cham hofn dong ho g i n vdri quan sat vien dufng
yen la:
A. 4,8 phut.
B. 20 phut.
C. 8 phut.
D. 7,2 phut.
ra:

Giai

Vi V = 0,8c nen J l - \ ^ 1 - 0 , 6 4 = 0,6.
Taco: At = ^ ^ ^ ^ = — - = 20.
0,6

rv

ThcJi gian chay cham hofn: t = At-Atg = 20 - 12 = 8 (phut).
Vdy chgn dap an C.
Cdu 60: Mot con \Ac vat li la m6t vat r^n c6 khoi lilgrng m = 4 kg dao
dong dieu hoa vdri chu ki T = 0,5s. Khoang each tCf trong t a m cua vat
den true quay cua no la d = 20 cm. Lay g = 10 m/s^ va =10. Momen
quan tinh cua vat doi v6i true quay la:
A. 0,025kg.ml
B. 0,64kg.ml
C. 0,05kg.m'.
D. 0,5kg.ml
GiSi

Taco: T = 2;r^
\mgd

Vdy chon dap an C.
Giai Chi tiSi
T^mgd^ 0,25.4.10.0,2 = 0,05(kg.m').
4.10
105


DE THI TUYEN SINH DAI HOC NAM 2011
Mon: VAT U - K h d l A
Thdi glan lam bai: 90 phut
Cho biet: H a n g so Plang h = 6,625. lO'^^J.s; do \6n dien tich nguyen
to e = 1,6.10"^^C; toe do a n h sang t r o n g ehan k h o n g e = S . l O W s ;
l u = 931,5 M e V / c l
Cdu 1: P h a t bieu nao sau day la d i i n g k h i n o i ve song ecf?
A. Biidc
cung m o t
.

song la khoang each giiJa h a i diem gan nhau n h a t t r e n

phucfng

t r u y e n song ma dao dong t a i h a i d i e m do cung pha.

B. Song ca t r u y e n t r o n g chat l o n g luon la. song ngang.
C. Song ccf t r u y e n t r o n g chat r a n luon la song doe.
D. Bu6c song la k h o a n g each

giOTa

h a i diem t r e n cung m o t

phiiofng

t r u y e n song ma dao dong t a i h a i diem do cung pha.

Glai
Bu'd'c song

la

k h o a n g each

pha t r e n cung m o t

phtTOng

ngSn

nhat

giijfa

h a i d i e m dao dong cung

t r u y e n song. Vqy chon dap an A.

Cdu 2: D a t d i e n ap u = u V 2 c o s 2 7 r f t ( U k h o n g d c i , t a n so f thay doi
diigfe) vao h a i dau doan mach mac n o i t i e p gom dien tror t h u a n R, cuon

can:- t h u a n c6 do tiT cam L va t u dien c6 dien dung C. K h i t a n so la fi
t h i cam k h a n g vk dung k h a n g cua doan mach eo gia t r i I a n

la 6 Q

va 8 Q . K h i t a n so la f2 t h i he so cong suat cua doan mach bSng 1. He
thufc l i e n he giiJa fi va ^2 l a :
A. f 2 = i f l .

B.

s

f 2 = — f l .

C.f2=

-fl.

D.f2=

-fl.

Giai
Ta c6: cos(p = 1 k h i mach xay r a cong hiidng hay i.^ =

271

V L C '

M a t khac ufng v d i fi t a c6: Z, = — Zp <=> 27if,L - —.—^—
1

\

o f , 2 =-f,^ <=>f, =

Vdy chgn dap an A.

106

Gi&i Chi m

(i6 thi T S D H , C D M6n V * t l(


Cdu 3: Gia

troiig mot

sijf

h a t triTdc p h a n

ufng h a t n h a n , t o n g k h o i liJOng c u a

phan

cac

ufng n h o hcfn t o n g k h o i lifgfng c a c h a t s a u p h a n ufng l a

0,02u. P h a n ufng h a t n h a n n a y :
A. t o a n a n g l i / o n g 1,863

MeV.

B. t h u n a n g liTcfng 1,863

MeV.

C. t o a n a n g liicfng 18,63

MeV.

D . t h u n a n g liTcfng 18,63

MeV.

Giai
A p dung cong thufc:
AE =

m^+mg -(m^. + mp)
'
V
'
tnldc phan I'mg

>

=-0,02.931,5 = -18,63 M e V .

^
'
sau phan ilng

Ta t h a y phan ufng t h u nang lucfng 18,63 M e V .
Vdy chon dap an D.
Cdu 4: Trong mach dao dong L C 11 tifdng dang c6 dao dong dien t\I t i i
do. T h d i gian ngSn n h a t de nang l U O n g dien triicfng g i a m til gia t r i cifc
dai xuong con m o t nufa gia t r i

CLTC

dai la l,5.10"'*s. T h d i gian ngSn n h a t

de dien t i c h t r e n t u g i a m tCr gia t r i ciic dai xuong con m o t nufa gia t r i
do la:
A. 2.10-^s.

B. 3.10-''s.

C. e.lO-^s.

D. 12.10-*s.

Giai
Ta c6:

2C

2 2C

•"

V2 '

T h d i gian nang liicfng dien g i a m tCf ctfc d a i xuong m o t nufa bang
thdi gian q g i a m tCr Q Q —>

:

'•

71

t = -:^ = ^
271

2TC

T

Y

= -

8

= l , 5 . 1 0 - ' s = > T = 12.10-^8.

Thc/i gian de d i e n t l c h g i a m tii cUc dai xuong m o t nufa:
t = ^ = i
= I = 2.10-s.
CO
27t
6
T
Vdy chon dap an A.
Giii Chi ti6t dS thi T S D H , C D M6n V$t I

107


Cdu

5: C h a t p h o n g x a p o l o n i

g°Po

phat ra t i a a va bien doi t h a n h

c h i ^s'Pb. C h o c h u k i b a n r a cua '^°Po

l a 138 n g a y . B a n d a u ( t = 0) c6

m o t m a u p o l o n i n g u y e n c h a t . T a i thofi d i e m t i , t i so giuTa so h a t n h a n
p o l o n i v a so h a t n h a n c h i t r o n g mku

la

. T a i thcfi d i e m t2 = t i + 276

n g a y , t i so giufa so h a t n h a n p o l o n i v a so h a t n h a n c h i t r o n g m l u l a
A.

25'

B.

16

C. i .

D.

9

_1_
15

Giai

93,75%

6,25%

4

1:7

87,5%

12,5%

3

1:3

75%

25%

2

1:1

50%

50%

1

AN,

No

No

AN,

N,

t
n = —
T

D i i a v a c b a n g suy r a t i = 2 T = 2 7 6 n g a y v a
t i n h la

N,

1:15
= 4 T . V a y t i le c a n

1:15.

Vay chgn
Cdu

dap

an

D.

6: M o t c h a t d i e m dao d o n g d i e u h o a t r e n t r u e O x . K h i c h a t d i e m

d i q u a v i t r i c a n b a n g t h i toe do cua n o l a 20 c m / s . K h i c h a t d i e m c6

t o e do l a 10 c m / s t h i g i a t o e cua n o c6 do 16n l a 4 0 \ / 3 c m / s ^ . B i e n do
dao d o n g c u a c h a t d i e m l a :
A. 4 cm.

B. 5 cm.

C. 8 e m .

D . 10 c m .

Giai
Taco:

(V,,CBU

Khi

2,

"

=

(1)

= 20 cm/s

( o ' A = 40V3 cm/s^

thi

T h a y (1) v a o (2) s u y r a : co = 4 ( r a d / s )
Vay chgn

dap

an

(2)

A = 5cm.

B.

t r u e CO d i n h

mot

7: M o t k h u n g d a y d f i n p h ^ n g q u a y d e u v d i t o e do g6c

Cdu

nam

t r o n g m a t p h d n g k h u n g day,

trtforng d i u co veetcf c a m ufng tCf v u o n g goc

co

quank,

t r o n g m o t tiif

vdfi t r u e q u a y cua k h u n g .

108

Gi4ichiti6t(3SthiTSDM,

CDMSnV^tK