Cdu 17: Mot con lit dan difcfc treo vao tran mot thang may.. Khi thang may chuyen dong thang dufng di len nhanh dan deu vdi gia toe c6 do Idfn a thi chu k i dao dong dieu hoa cua con la
Trang 1Cdu 12: M o t l a n g k i n h c6 goc chiet quang A = 6° (coi la goc nho) dtfcfc
dat trong khong k h i Chieu mot chum a n h sang trSng song song, hep
vao mat ben cua lang k i n h theo phifcng vuong goc vdi m a t phang phan
giac cua goc chiet quang, r a t gan canh cua lang k i n h D a t mot m a n E
sau lang k i n h , vuong goc vdi phucfng cua chCim t i a t<Ji va each m a t
phang phan giac cua goc chiet quang 1,2 m Chiet suat cua l a n g k i n h
doi vdi anh sang do la n^ = 1,642 va doi vori anh sang t i m la nt = 1,685
Do rong ti^ mau do den mau t i m cua quang pho l i e n tuc quan sat dUdc
tren m a n la
A 36,9 m m B 10,1 m m C 5,4 m m D 4,5 m m
Giai
Ta c6:
DT = L ( n , - n j A - l , 2 ( l , 6 8 5 - l , 6 4 2 ) 6 — = 5,4.10"'m = 5,4mm
180
rad
Vdy chgn dap an C ^ Cdu 13: ThiTc h i e n t h i nghiem Y-ang ve giao thoa vdri a n h sang dcfn
sic mau lam ta quan sat difofc he van giao thoa t r e n m a n Neu thay
anh sang dcfn sic mau lam bang anh sang dan sac mau vang va cac
dieu k i e n khac ciia t h i nghiem dtrgfc giiif nguyen t h i
A khoang v a n k h o n g thay doi B v i t r i v a n t r u n g t a m thay doi
C khoang van t a n g len D khoang v a n giam xuong
Ta c6: 1= — V i X vang > X\am nen khoang van i t a n g len k h i thay
lam
bang X v a n g
-Vay chgn dap an C
Cdu 14: Doan mach A B gom hai doan mach A M va M B mac n o i tiep
Doan mach A M gom dien t r d thuan- 3 R i = 4 0 Q mSc n o i tiep vdi tu
dien c6 dien dung C = ^ - ^ F , doan mach M B gom d i e n t r d t h u a n R 2
471 • •
mac r o i tiep voi cuon cam t h u a n Dat vao A, B dien ap xoay chieu c6
gia t r i hieu dung va t a n so k h o n g doi t h i dien ap tufc thcfi of h a i dau
111
Trang 2do an m ac
h A
M v
a M
B I an
\\iat
l a:
UA
M = 50>y2
co
sf 10
0;
rt
- —
U|^B = 150cosl007rt
(V )
He
so co ng s ua
t cii
a d oa
n ma ch A
B l
a:
(V
) v
a
A 0,84
Ta c6:
B
0, 71
C 0,95
D 0,86
Giai
7c
In
7 1
9M B=
0-9i
=
-U^B
= UI
M +U
L + 2U ,^
.U MB CO S^
= 10 4,8
V 12
U^ecoscp = U^^
, -coscp^^
, +
U^3Cos
(p^,B ^ cosc
p = 0,84
Vay chon dap an
A
Cau 15:
M ot c ha
t d ie
m da
o don
g die
u ho
a the
o phirorn
g t ri nh = 4co
—
(x
t in
h ba ng c m; t t in
h bk ng s)
Ke t
tf t = 0 , c ha
t di em d
i q ua
v
i t
ri c
6
li d
o X
=
-2 cm I an thuf 20 11
ai th
di di em :
A 30 16
s
B
30 15
s C 603
0 s
D
60 31
s
Giai
Nhdn xet:
Q ua
y mo
t v on
g c
6 2 I an c an t im
; qua
y 100
5
vo
ng
c6
20 10 I an c an t im d on
g tho'
i va
t t rd ve d un
g v
i t
ri bi en b an
d
au
; qua
y
th em m ot goc ^ t
hi va
t d
i t he
m m ot I an njjfa
Va
y to ng go
c qu
et
c p =
1005(27:
)
+ ^ = =
> t = 30 16 (s )
Vay chqn dap an
A
Cdu 16:
T he
o th uy
et ti/cfn
g doi,
m ot e le ct ro
n c
6 do ng n an
g
bS
ng
m
ot
nijfa na ng luofng ng
hi cu
a n
o t
hi ele ct ro
n n ay c hu ye
n d on
g vdr
i to
e d
o bang
:
A, 2,41.10^nVs
B
2, 24 1 0V
s
C 1, 67 l OW
s ' D
2, 75 1 0W
s
Giai
Ta co : Wd = E -E o=
^ Eo
^E
=^
Eo
112
Giai Ch i
m d
e th
i T
S DH
, C
D M6
n Va
t l
i
Trang 32 -i
= -moc' « v = 2,24.10'm/s
1
-Vdy chgn dap an B
Cdu 17: Mot con lit dan difcfc treo vao tran mot thang may Khi thang
may chuyen dong thang dufng di len nhanh dan deu vdi gia toe c6 do Idfn a thi chu k i dao dong dieu hoa cua con lac la 2,52s Khi thang may chuyen dong thing dufng di len cham dan deu vdri gia toe eung c6 do Idn a thi chu k i dao dong dieu hoa cua eon l i e la 3,15s Khi thang may dufng yen thi chu k i dao dong dieu hoa cua con l&c la:
A 2,84 s B 2,96 s C 2,61 s D 2,78 s
Giai
* Khi nhanh dan thi f giam dan, khi do dong ho ehay nhanh Suy ra T i < TQ
g + a -•To^g + a = g (1)
* Khi cham dan' thi f tang dan, khi do dong ho ehay eham Suy ra Tg > TQ
V g - a
Vay chgn dap an D
Cdu 18: Mot chat phat quang diicfc kich thich bang anh sang c6 bifdc
song 0,26 |am thi phat ra ^nh sang c6 btfdc song 0,52 ^ m Gia suf cong
suat cua chum sang phat quang hkng 20% cong suat cua chum sdng
kich thich Ti so giufa so photon anh sang phat quang va so photon anh sang kich thich trong cung mot khoang thoi gian la:
10"
Giai
Cong thufe anh sang kich thich: P^., = N he