ndy sang m6i trudng kh6c thi tAn sO (cf,ng nhu chu ki) cira s6ng kh6ng thay d6i cdn bu6c
s6ng cira s6ng thi thay ddi. S6ng diQn tu truy6n
dugc trong chAn kh6ng, cdn s6ng co thi kh6ng truy6n dugc trong chdn kh6ng.
*Thi dU l. Xdc clinh bi€n d0 A vci pha
ban diu rp cia mQt dao dQng diiu hod
x = Acos(4rur + q)(cm). Bi6t rdng tqi thd'i
tti€m t6 : A vil cd li d0 r0 = 1 cm. tai thoi ,1 diiirrt rt : )'s vqr ci ti ct6 rr = 16 cn',. () Hmimg ddn gidi Khi f - to = 0 =x6 =,4cosrP = 1 cm (1) hay x1= -lsing = .,,6 cm Tt (1) vd (2) suy ra (2) = J + 3 = 2cm tanqr: -* = -..5 = ,p: -+ Khi d6
x = Acos(+rt +e)= 2cos (0", -i) t""1..
*Thi dttr 2. Trong mach dao dQng LC co doo cl|ng di€n tir ttr da. Tu di€n cd diQn clung
C = lpF, cuQn cdm co d6 ng cdm L = l,0nrH.
Bi€t di€n tlch cryc dai tr€n m\t bdn tu diQn lci 4.10-ec.
a) Xac dinh tin td doo tl6ng ri€ng cua mach.
b) Tirn brcrr: song ctia song di€n ti.r md ntach
ndy c6ng hudng.
c) Chqn g6c thd'i gian t : 0 ld l{rc tw di€n bat
ddu phong di€n, viilt biiju thac ardng dQ ddng
diQn trong mgch.
Hwdng ddn gidi. a) Ta c6
Khi r=r,:*s e.x1 =o*r(}+,p) .-6oq
*E+tJLC fr,1101 to* JLC fr,1101 to* ,A ToRN H9c...."... 6r6b 'GtrrdiUA Y,/ Wc aaa. aA 9
Tu bi6u thric
a = 2nf +.[ : *= * = 15923,s (Hz).
b) Bu6c s6ng )" = c.T, trong d6 c ld v6n t6c 6nh siing trong ch6n khong, f :4. Khi
CD
cQng hucmg thiro =
)\-z1tL'=2rct[LC
.l*
= 2.3,14.3.1dV0,l.l0-r.l.l0{ = 1.88.104 (m).c) N6u chon g6c thoi gian /: 0 ld hic tu diQn c) N6u chon g6c thoi gian /: 0 ld hic tu diQn
UitOauph6ngdiQnthi q : qo, suyra e = 0.
Do clo q : qocosruot; cudng dQ ddng diQn
-2 -2
w, :
lC =
#cos2 (r,rr + <p).
-Ndng lugng tu truong tfp trung 6 cu6n cdm
ill Li" 1 , 1 1/
n/t = 2 = lo|Lar sinz (oll + q)
)
qd ^:.
- -------;- 2c. Jrln21ror + q;.
- Ndng lugng diQn tu trong mach dao dQng ZC
b6o todn
[4/ =wc +wL = *: + =ry: aonst.B
*Thi dtt 3. MQt con liic ld xo co ttQ c*ng
/r : l00N/r'n duo ddng diiu hod voi bi€n ctt)
A:6cm.
a) Tinh thl nang vd d6ng ndng c'ia con ldc, khi
li cl6 r:ticr t,ot l:tting *3cm.
b) iVitt tliat' qua c'iu ct)u con ldc bing mot qurt
ciu khtic' co khoi lu'ottg tcn giip 4 lin qua ciu
nuo'c thi c'hu ki vt) c'o'ndng c:ua con ldc thal dt)i
the nt)o'l BiAt hi€n dQ cira dao ttQng tchdng tloi.
Hming ddn gidl a) Co ning ctra con lEc
kA2 7 , ^r2w : w : ; = r.100.(6.10-r) = 0,18(J). Th6 n[ng cua con l6c a 100. [-3.10-r ) =lOsrad/s.Tac6 Jrc . dq ( r\ i :
# = Qo(isin rrrt : {socosIr,. i.,]
/ n)
hay i =locoslror+51
\ .)
voi Io : (nQo: 10s.4.10-e = 4.10-4(4).
vay i = 4.lo+cos (rct, **l tof o
\ z)
DANG 2. Kh:io sft triri tAp dao tlQng vi s6ng
theo phuong phdp ning lugng Phrang phdp gidi
- MOt vflt kh6i lucrng m, dao dQng di6u hod
voi li dQ x : Acos(ror + q), thi c6 vdn t6c
dr
, = ; = -rolsin (r,rl + g) ve d6ng ning
I , *a2A2 .1r
Wa = lntv' =, sin'(<rrf +<p).
- LUc k6o v0 F = -Ax ldm vAt dao dQng cli6u hod vdi th6 ndng
wl : ;# : ;ru,?i = rycos2 (ror + e).
- Co ndng cira vdt dao ctQng diAu hod b6o todn
bA2 ma2A2
W : Wa *W, =
T =;: corSt.