Lecture 8 Notes

# Lecture 8 Notes - Today Forced vibrations Newtons 2nd Law...

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Today • Forced vibrations • Newton’s 2nd Law with external forcing. • Forced mass-spring system without damping away from resonance. • Forced mass-spring system without damping at resonance. • Forced mass-spring system with damping. • Review questions.

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Forced vibrations (3.8) • Newton’s 2nd Law: ma = kx γ v + F ( t )
Forced vibrations (3.8) • Newton’s 2nd Law: ma = kx γ v + F ( t ) spring force

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Forced vibrations (3.8) • Newton’s 2nd Law: ma = kx γ v + F ( t ) spring force drag force
Forced vibrations (3.8) • Newton’s 2nd Law: ma = kx γ v + F ( t ) spring force drag force applied/external force

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Forced vibrations (3.8) • Newton’s 2nd Law: ma = kx γ v + F ( t ) mx °° + γ x ° + = F ( t ) spring force drag force applied/external force
Forced vibrations (3.8) • Newton’s 2nd Law: ma = kx γ v + F ( t ) mx °° + γ x ° + = F ( t ) spring force drag force applied/external force • Forced vibrations - nonhomogeneous linear equation with constant coef±cients.

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Forced vibrations (3.8) • Newton’s 2nd Law: ma = kx γ v + F ( t ) mx °° + γ x ° + = F ( t ) spring force drag force applied/external force • Forced vibrations - nonhomogeneous linear equation with constant coef±cients. • Building during earthquake, tuning fork near instrument, car over washboard road, polar bond under EM stimulus (classical, not quantum).
Forced vibrations (3.8) • Without damping ( ). γ =0

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Forced vibrations (3.8) • Without damping ( ). γ =0 mx °° + kx = F 0 cos( ω t )
Forced vibrations (3.8) • Without damping ( ). γ =0 mx °° + kx = F 0 cos( ω t ) forcing frequency

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Forced vibrations (3.8) • Without damping ( ). γ =0 mx °° + kx = F 0 cos( ω t ) mx °° + forcing frequency
Forced vibrations (3.8) • Without damping ( ). γ =0 mx °° + kx = F 0 cos( ω t ) mx °° + x h ( t )= C 1 cos( ω 0 t )+ C 2 sin( ω 0 t ) forcing frequency

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Forced vibrations (3.8) • Without damping ( ). γ =0 mx °° + kx = F 0 cos( ω t ) mx °° + x h ( t )= C 1 cos( ω 0 t )+ C 2 sin( ω 0 t ) ω 0 =? forcing frequency
Forced vibrations (3.8) • Without damping ( ). γ =0 mx °° + kx = F 0 cos( ω t ) mx °° + x h ( t )= C 1 cos( ω 0 t )+ C 2 sin( ω 0 t ) ω 0 = ° k m forcing frequency

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Forced vibrations (3.8) • Without damping ( ). γ =0 mx °° + kx = F 0 cos( ω t ) mx °° + x h ( t )= C 1 cos( ω 0 t )+ C 2 sin( ω 0 t ) ω 0 = ° k m natural frequency forcing frequency
Forced vibrations (3.8) • Without damping ( ). γ =0 mx °° + kx = F 0 cos( ω t ) mx °° + x h ( t )= C 1 cos( ω 0 t )+ C 2 sin( ω 0 t ) ω 0 = ° k m • Case 1: ω ° = ω 0 natural frequency forcing frequency

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Forced vibrations (3.8) • Without damping ( ). γ =0 mx °° + kx = F 0 cos( ω t ) mx °° + x h ( t )= C 1 cos( ω 0 t )+ C 2 sin( ω 0 t ) ω 0 = ° k m • Case 1: ω ° = ω 0 natural frequency forcing frequency x p ( t A cos( ω t B sin( ω t )
Forced vibrations (3.8) • Without damping ( ).

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Lecture 8 Notes - Today Forced vibrations Newtons 2nd Law...

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