23. 1. , , v . M, m. A ?
? , , . , .
? (20.15). , (20.15) :1) , 2) .
m v2 / 2 + M u2 / 2 0 = A. (23.1)
. u. , . A A.
(23.1) , : A u. (20.2). .:
m v M u = 0. (23.2)
(23.2) (23.1)
A = m v2 (1 + m /M) / 2.
, , . m << M .
.
.
23. 2. m1, v , m2. ? , .
50 , . 1 , . 50 .
u1 u2, , .
x (. 50) :
m1 u1X + m2 u2 m1 v = 0. (23.3)
(23.3) u1X 1, . u1X , 1.
:
m1 u1X2 / 2 + m2 u22 / 2 m1 v2/ 2 = A + A. (23.4)
A ( ) , . A , .
(23.3) (23.4) :
u2 = ; u1X = . (23.5)
, u1X > 0 ( 1 x), m1 > m2. 50 m1 < m2. m1 = m2, u1X = 0, u2 = v . m1 << m2 u2 << v, u1X v; , , .
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23. 3. E0 , 600. , .
, , ? , : , . , , ( ) , , , a (. 51). 2, b .
? , .
, m. : (. 51).
(20.2)
m 1 + m 2 m = 0. (23.6)
(23.6) , .
(20.15)
m v12 / 2 + m v22 / 2 m v2/ 2 = 0. (23.7)
A ( ) , , . A : , , .
? ? ? :
E0 = m v2/ 2; E1 = m v12 / 2; E2 = m v22 / 2. (23.8)
2 b (. 51). ? (23.6) x y (. 51). , v1, v2 b. . (23.6) , 51. (23.7) :
(m v2) = (m v12) + (m v22). (23.9)
(23.9) , 51, , , .
b:
b = 900 600 = 300.
v1 = v / 2, v2 = v / 2. (23.10)
(23.10) (23.8), :
E1 = E0 / 4, E2 = 3 E0 / 4.
.
.
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23. 4. , , . m1 m2, , , v1 v2.
? ? 22. 7 . . , , . , . . , 22. 7, :
Q = A. (23.11)
A? (20.15). (.52):
(m1 + m2) v2/ 2 (m1 v12 / 2 + m2 v22 / 2) = A. (23.12)
. ( ) . A A.
? , : Q, A, v. (20.2) x (. 52). . , 52 . . - vX .
(m1 + m2) vX (m1 v1 m2 v2) = 0. (23.13)
(23.13)
vX = (m1 v1 m2 v2) / (m1 + m2). (23.14)
(23.14) : , .
, v2 = vX2, (23.14), (23.11) (23.12).
Q = .
23. 5*. M l . m, a . , ? ?
, , . .
1 l (. 53). , 2. (M + m) . , , . , Q, , , , , . . , -, (54).
-, , ( ) ( ). - , .
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-. , , F = 0:
(M + m) a = (M +m) g. (23.15)
u2 , -:
a = u22 / l. (23.16)
() (20.15) (. 53), u1 u2. .
(M + m) g 2 l + (M + m) u22 / 2 (M + m) u12 / 2 = 0. (23.17)
. . A = 0. . , .
v () (20.2). . , . .
(M + m) u1 m v cos a = 0. (23.18)
Q . Q () (20.15):
(M + m) u12 / 2 m v2 / 2 = A, A = Q. (23.19)
( ). :
v = , Q = .
.
, -.
. , , , . , , .
, , . .
, : , . . , , , , .
x ,
x = x0 sin (w t + j0) (24.1)
(24.1) x0 , w , j0 .
T = 2 p / w. n = 1 / T =,
w / (2 p), .
24. 1. R w. x, ? ?
55 , . - ? . (3.9) (3.11). 55 ,
x = R sin j . (24.2)
j :
j = j0 + w t, (24.3)
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(3.11). j0 j t = 0.
(24.3) (24.2)
x = R sin (w t + j0), (24.4)
x .
x (. 55) (3.6),
vX = R w cos (w t + j0). (24.5)
, , , (24.4).
(. 55), , (3.10). x (. 55)
aX = R w2 sin (w t + j0). (24.6)
(24.6), , (24.5).
(24.4), (24.6) :
aX = w2 x. (24.7)
vX aX, x, .
, , , (24.7) , (24.1), .
x (24.1) (24.7).
x . , w , j , .
24. 2. m. , , k. . .
T w T = 2 p / w, (24.7). , x ( 56):
m aX = m g 2 F. (24.8)
F , , . , :
F = k D l, (24.9)
D l , x , .
x D l? 17.2. x, 2 x,
D l = 2 x. (24.10)
(24.9) (24.10) (24.8),
aX = 4 (k / m) x + g. (24.11)
(24.11) (24.7)? , x? aX? , x. (24.11):
aX = 4 (k / m) (x m g / (4 k)) Þ
aX = w2 x¢, (24.12)
w2 = 4 k / m, (24.13)
x¢ = x m g / (4 k). (24.14)
x¢. x = x0 = m g / (4 k), x¢ x x0. x = x0 x¢ aX. , x¢, , .
(24.13):
T = 2 p / w = p .
24. 3. , 0, l . , ?
0 = 0, , , .
:
m = m + . (24.15)
= , (. 57).
= 0, (24.15) , m . , ( . 57).
¹ 0. (24.15) x, , .
m aX = m g sin j.
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j, sin j j x / l, , j (. 57).
m aX = m g x / l,
(24.7),
w2 = g / l, T = 2 p . (24.16)
, , ( ) . (24.16). .
, , 0 ¹ 0.
, . (24.15)
m = m + . (24.17)
= , (3.5):
= + = + 0. (24.18)
(24.17) (24.18)
m = m ( 0) + . (24.19)
(24.19) (24.15), ,
¢ = 0. (24.20)
, 0 , ¢, (24.20).
¢. , (24.20) 0.
(24.16) ¢:
T = 2 p .
(24.7).
, .
¢ = 0 , , 0 = 0. , , .
24. 4. , 58, m1 m2 , . k . , , . , .
(24.7). m1 x m2 y (.58):
m1 a1 = F1 k x, (24.21)
m2 a2 = m2 g F2, (24.22)
1 2 , , x (. 58).
a1 = a2 = aX F1 = F2 = F.
(24.21) (24.22)
(m1 + m2) aX = m2 g k x.
aX = .
(24.7) w2 = k / (m1 + m2), :
T = = 2 p .
x¢ = x x0, x0 = m2 g / k. (24.23)
x0 , aX = 0.
, , (20.15) , , .
, x. (E1 = 0). (E1 = 0).
E1 = E1 + E1 = 0.
, :
E2 = k x2 / 2 m2 g x.
(20.15) : , . E2 E1 = 0,
k x2 / 2 m2 g x = 0.
, x = 2 m2 g / k. (24.24)
(24.24) (24.23), , . , x0 , . , x = x0 = m2 g / k.
() , ().
.