Class 15: Calculation of natural frequency Class 15: Calculation of - - PowerPoint PPT Presentation

class 15 calculation of natural frequency class 15
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Class 15: Calculation of natural frequency Class 15: Calculation of - - PowerPoint PPT Presentation

Class 15: Calculation of natural frequency Class 15: Calculation of natural frequency Old Slide Origin of simple harmonic motion U(x) = kx 2 Total energy Total energy F = - kx x V=0 a is max V=0, a is max. V=0 a is max V=0, a is max. a=0, v


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SLIDE 1

Class 15: Calculation of natural frequency Class 15: Calculation of natural frequency

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SLIDE 2

Origin of simple harmonic motion Old Slide U(x) = ½ kx2 Total energy Total energy

kx

  • F=

x V=0 a is max V=0 a is max V=0, a is max. V=0, a is max. a=0, v is max.

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SLIDE 3

Arbitrary potential Arbitrary potential Taylor expansion of arbitrary potential about x=x :

L ) x

  • x

)( (x U" 1 ) x

  • x

)( (x U' ) U(x U(x)

2

+ + + =

Taylor expansion of arbitrary potential about x=x0:

) )( ( 2 ) )( ( ) ( ( )

F i l h i i For simple harmonic motion, U(x0) ‐‐‐ Irrelevant, just an offset U’( ) 0 Si l h i i U’(x0)=0 ‐‐‐ Simple harmonic motion always occur at the i i t ti l minimum potential

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SLIDE 4

Simple harmonic motion of arbitrary potential Given arbitrary potential U(x) Suppose U(x )=0

) x x )( (x U" 1 ) U(x U(x)

2

+

Given arbitrary potential U(x). Suppose U(x0)=0

) x

  • x

)( (x U" 2 ) U(x U(x)

0 +

≈ ) (x U" k = ∴ ) (x U" k = = ω m m