1. §12.3 二维简谐振动的合成
)cos( 11 ϕω += tAx CAI
)cos( 22 ϕω += tAy
)(sin)cos(
2
12
2
12
21
2
2
2
2
1
2
ϕϕϕϕ −=−−+
AA
xy
A
y
A
x
)210(2)1( 12 ,...,,kk ±±==− πϕϕ
x
y
O 1A
2Ax
A
A
y
1
2
=
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2. )210()12()2( 12 ,...,,kk ±±=+=− πϕϕ
x
y
O
1A
2A
x
A
A
y
1
2
−=
)210(2
2
)3( 12 ,...,,kk ±±=+=− π
π
ϕϕ
x
y
2A
1A
12
2
2
2
1
2
=+
A
y
A
x
沿顺时针方向运动CAI
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3. )210(2
2
)4( 12 ,...,,kk ±±=+−=− π
π
ϕϕ
x
y
2A
1A
12
2
2
2
1
2
=+
A
y
A
x
沿逆时针方向运动
12)5( ϕϕ − 为其它量值
x
y
斜椭圆
CAI
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4. dt
xd
bvbFd
r
rr
−=−=
2
2
dt
xd
m
dt
dx
bkx =−−
m
b
m
k
o == αω 22
α damping factor
1.阻尼振动
02
2
2
2
=++ x
dt
dx
dt
xd
oωα
Damped Harmonic Motion
natural frequency0
damping force
b 阻尼系数 damping coefficient
ω
§12.3 阻尼振动和受迫振动
阻尼因子
CAI
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固有角频率
11. Turbulent winds set up standing waves in the
Tacoma Narrows suspension bridge leading to
its collapse on November 7, 1940, just four
months after it had been opened for traffic
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