1. = 3 , = 0,2 l = 1,2 . , = 2 , : ) ux,t t = 7 ; ) . .
:
= 3
= 0,2
l = 1,2
= 2
t = 7
_______________
ux,t ? 
x,t ? 
x,t ?
. г :
ux,t = A cos (wt - kx), (1)
w = 2p/ ;
k = 2p/l .
(1):
; (2)
. (3)
) = 2 t = 7 ,
)
=
= 0,2 × 10-3.2093 sin 
= 0,031 /.
)
=
= 0,2.10-3.20932 s 
= 873,3 /2.
³: ux,t = 0,12 ; 
= 0,031 /; = 873,3 /2.
2. г
ux,t = 6,0 ×10-2 cos (1800t 5,3x) . (1)
: ) ; ) ; ) .
. г :
ux,t = A cos 
. (2)
) (1) (2), . , :
= 6,0 × 10-5 ; 2 p/ = 1800 -1,
= 2p/1800 = 3,49 × 10-3 .
2p/l = 5,3 -1, l = 2p/5,3 = 1,18 .
= 5,08 × 10-5.
) , (1)
= 6,0 × 10-5 × 1800 sin (1800×t 5,3×x) /,
(
)max = 6,0 × 10-5 × 1800 = 0,11 / .
= 339 /.
³
) (2):
;(3)
; (4)
(4) (3)
=υ
;
;
υ .
³: /l = 5,08 × 10-5; = 0,11 /;
= 3,19 × 10-4; 
.
3. 85 . 340 /, , n0 = 1250 . : ) ; ) .
|
|
|
:
l = 0,85
υ = 340 /
n0 = 1250
____________
n1 ? n2 ?...
. , . , , , .7.
7
) l/4,
l = (2k +1) l/4,
k = 0, 1, 2,...;
l , l = υ/n.
l = (2k + 1) 
, n = 
.
k = 0; n1 = 
= 100 .
k = 1; n2 = 
= 300 .
k = 2; n3 = 
= 500 .
k = 3; n4 = 
= 700 .
k = 4; n5 = 
= 900 .
k = 5; n6 = 
= 1100 .
n6;
) , , , ,
l = k 
, k = 1, 2, 3,....
, l = 
,
l = k 
, n = 
.
k = 1; n1 = 
= 200 . k = 2; n2 = 
= 400 .
k = 3; n3 = 
= 600 . k = 4; n4 = 
= 800 .
k = 5; n5 = 
= 1000 . k = 6; n6 = 
= 1200 .
4. u1 = 30 /c u2 = 20 /. n1 = 600 . , 䳺 : ) ; ) . c = 340 /.
:
u1 = 30 /
u2 = 20 /
n0 = 600
c = 340 /
____________
? 
?
. :
)
× 600 = 696 ;
)
× 600 = 519 .
³: 
= 696 ; 
= 519 .
5. , r = 25 R 20 /2. 㳿 
?
:
r = 25
R = 20 /2
_____________
N ? ?
. ³, 㳿
R = 
,
W , ;
S , 㳿;
Dt .
N = 
N = R S.
ϳ
N = 20 × 10-3 × 4 × 3,14 × 625 = 157 .
ᒺ 㳿
R = 
= 
,
, 340 /.
5,88 × 10-5 /3.
³: 157 ; 5,85×10-5 /3.
