, (, ) .
s(t,x)=Acos[w (tx/c)]Acos[w (t+x/c)]=2Asin[w x/c]sinw t
w, : ()=2|sin[wx/c]|
, . . ( ) ( , ).
, . ( ) .
, , . , , , . .
:
, , .. ( ) , . . .
, . , .
L = n l/2,
l- , L, n .
27.
. , . dA = FdS = FdScosa.
, 0 , , : , . F L. 2- .
F=dp/dt, ds=v dt Þ A=ò(v dp)=[p=mv, v dp=mv dv, ]=mv2/2. A12=m , 1 2. K=(mv2/2)=p2/2m . . . . . . .., - .
|
|
? : v=v+V Þ (Mv2)/2 = (mv2)/2 + (mV2)/2 + mvV
K =K+(mV2)/2+(pV), =mv S.
. . ( ) K=K+(mV2)/2 + m(Vv)/2
ʸ:
. . . , , . . .
28.
. . . , :
Dpi=mivi dmi XYZ, ri - dmi , . L w., , m, (. 2.3). w , . :
L=mri´vi+ mr2´v2=2mr2w, , : r1 =r2 =r, v1=v1=wr.
, L , w. , . , . 2.4. L , . ri - Dmi , w . :
ri, w L XYZ, xyz, ( , ). xyz , r i ( XYZ ), L .
. Jxy=Jyx, Jxz=Jzx, Jzy=Jyz, . .
Ox, Oy, Oz , . Jxx=Jx, Jyy=Jy, Jxx=Jz . , : Lx=Jxwx . . . .
, . , , . , .
. , . , , . , , . , . . . Jxx, Jyy, Jxx.
|
|
29.
. , .
, .
, .
. . . , . , . . , N W . , .
2.
, . . ( ) ( , ).
, . ( ) .
() - , 20 20 000 .
. . , s, dx.
r0 s dx 2S/t2 = [Px Px+dx] s
r0 2S/t2 = - P/x
p0:
dP=(P/r)r0 dp=c2 dr
-P/x=-c2 dr/x=c2 /x[r0 (-S/x)]=c2ro 2S/x2
2S/t2 = c2 2S/x2, c2= P/r, r=r0
:
P=rRT/m P=const rg g=/V dP/dr= g const rg-1= g P0/r0 Þ
Þ C2=g P0/r0= g RT/m
, x .
x, , , , -: .
, -: .
, -. (5)
: .(6)
(5) (6) Þ (7)
dv/v0=dr/r0 (8)
dp/dr=g p0/r0
(8),(9) Þ Dp= g p Dr /r =g pu/c=r cu, .. (1). (10)
. - . , SDx. h= dv/v0, (10) , S, SDp =ghp. dh Dx× dh dA=S×Dx×gp×h×dh.
u=SDxg p
wU=g ph2/2 (14)
T=r SDxu2/2 wT= ru2/2. (7) , wU=wT. w=gp×h2. .. h cos, h2 cos2, h2=h02/2, w =g ph02/2. .. (7) D h, Þ w =(Dp0)2c/2g p, Dp0 - .
|
|
, , , .
I= w c=(Dp0)2c/2g p = =(Dp0)2/2r c (. . 2=g p/r) /2×.
30.
1.
. XYZ x 0 y 0 z 0, , , : j=j(t), y=y(t), q=q(t).
: , , j , . C : , . , . XYZ ( x 0 y 0 z 0) . . xyz, , . : v=w´r, r - XYZ ( x 0 y 0 z 0), .
2. . , , . , . , v /, , : , . . , / , +v f 1 (f-), 1 , f=f/(1+v/c) , f=f/(1-v/c); , , v 1 f, f , f=f(1+v/c) f=f(1-v/c);