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Dynamics cheat sheet

my dynamics notes - 12000.org

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Hence<br />

The first eigen vector is<br />

Similarly for ω 2 = 0.438<br />

ϕ 21 = 0.475<br />

−2 = −0.237<br />

⎧ ⎫ ⎧ ⎫<br />

⎨ϕ 11 ⎬ ⎨<br />

ϕ 1 =<br />

⎩<br />

ϕ<br />

⎭ = 1 ⎬<br />

⎩<br />

21 −0.237<br />

⎭<br />

⎛⎡<br />

⎤ ⎡ ⎤⎞<br />

⎧ ⎫ ⎧ ⎫<br />

⎝⎣ 3 −2 ⎦ − 0.438 2 ⎣ 1 0 ⎨ϕ ⎦⎠<br />

12 ⎬ ⎨<br />

−2 2<br />

0 3<br />

⎩<br />

ϕ<br />

⎭ = 0⎬<br />

⎩<br />

22 0<br />

⎭<br />

⎡<br />

⎤ ⎧ ⎫ ⎧ ⎫<br />

⎣ 2.808 −2 ⎨ 1 ⎬ ⎨<br />

⎦<br />

−2 1.425<br />

⎩<br />

ϕ<br />

⎭ = 0⎬<br />

⎩<br />

22 0<br />

⎭<br />

This gives one equation to solve for ϕ 22 (the first row equation is only used)<br />

2.808 − 2ϕ 22 = 0<br />

Hence<br />

The second eigen vector is<br />

ϕ 22 = −2.808<br />

−2<br />

= 1.404<br />

⎧ ⎫ ⎧ ⎫<br />

⎨ϕ 12 ⎬ ⎨<br />

ϕ 2 =<br />

⎩<br />

ϕ<br />

⎭ = 1 ⎬<br />

⎩<br />

22 1.404<br />

⎭<br />

Now step 4 is applied, which is mass normalization of the shape vectors (or the eigenvectors)<br />

µ 1 = ϕ T 1 [M] ϕ 1<br />

Hence<br />

Similarly, µ 2 is found<br />

Hence<br />

⎧ ⎫<br />

⎨ 1 ⎬<br />

µ 1 =<br />

⎩<br />

−0.237<br />

⎭<br />

= 1. 169<br />

⎧ ⎫<br />

⎨ 1 ⎬<br />

µ 2 =<br />

⎩<br />

1.404<br />

⎭<br />

= 6.914<br />

⎤ ⎧ ⎫<br />

⎣ 1 0 ⎨ 1 ⎬<br />

⎦<br />

0 3<br />

⎩<br />

−0.237<br />

⎭<br />

T ⎡<br />

µ 2 = ϕ T 2 [M] ϕ 2<br />

⎤ ⎧ ⎫<br />

⎣ 1 0 ⎨ 1 ⎬<br />

⎦<br />

0 3<br />

⎩<br />

1.404<br />

⎭<br />

T ⎡<br />

11

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