We said above that G(w) does not depend on the number of people or their mass, and that it increases with smaller B; why are these state- ments true? Which terms in Equation 5 persist for large times? For large times, what happens to the dependence of the solution on the initial conditions? What is the amplitude of the equilibrium oscillation in Equation 5? How does the gain function relate the amplitude of the equilibrium oscillation to the amplitude of a forcing term in the form of Equation 3? In particular, what is the maximum displacement of the bridge given a gain function G(w), a walking frequency w, a number of people N, and the lateral force per person W?

Elements Of Electromagnetics
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ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Sadiku, Matthew N. O.
ChapterMA: Math Assessment
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Please show all work for Exercise 2 please!

The general solution to Equation 3, unless w = √ and B = 0, is
X(t) = G₁e¬Bt/(2M) cos (t√/1² – (B/(2M)}²)
+ C₂e-B²/(2M) sin t√√23 - (B/(2M))²)
NW
(5)
Bw
- cos (wt -atan (M(W² 525)))
/M² (S2² - w²)² + B²w²
where
and atan(x) = arctan(x), the inverse tangent of x. It is useful
to have a measure of how a certain system (for this lab, the bridge), amplifies or
reduces forces (resulting from walking humans) applied to it. The ratio of the
amplitude of the input (i.e., the right hand side of the equation) to the long-
term amplitude of the output (i.e., the solution to the differential equation) as
a function of input frequency is called gain (we explore this in class in §4.6 of
Brannan & Boyce). The gain function for Equation 3 is
1
(6)
G(w) =.
/M² (S2²3 - w²)² + B²w²
There are a number of important observations to make about G(w): (1) be-
cause it's a ratio of output to input amplitudes, it doesn't depend on the input
amplitude (for our bridge, the number of people or their mass); (2) it gets larger
as the damping B decreases; and (3) in general, it gets larger as the forcing
frequency w approaches the value 2o-though the maximum amplitude will not
occur exactly at w = No. (Be sure you can see how these are reflected in the
expression above.)
Exercise 2: The primary utility of the gain function is to tell us how the
solution to an oscillator responds to a forcing term.
Transcribed Image Text:The general solution to Equation 3, unless w = √ and B = 0, is X(t) = G₁e¬Bt/(2M) cos (t√/1² – (B/(2M)}²) + C₂e-B²/(2M) sin t√√23 - (B/(2M))²) NW (5) Bw - cos (wt -atan (M(W² 525))) /M² (S2² - w²)² + B²w² where and atan(x) = arctan(x), the inverse tangent of x. It is useful to have a measure of how a certain system (for this lab, the bridge), amplifies or reduces forces (resulting from walking humans) applied to it. The ratio of the amplitude of the input (i.e., the right hand side of the equation) to the long- term amplitude of the output (i.e., the solution to the differential equation) as a function of input frequency is called gain (we explore this in class in §4.6 of Brannan & Boyce). The gain function for Equation 3 is 1 (6) G(w) =. /M² (S2²3 - w²)² + B²w² There are a number of important observations to make about G(w): (1) be- cause it's a ratio of output to input amplitudes, it doesn't depend on the input amplitude (for our bridge, the number of people or their mass); (2) it gets larger as the damping B decreases; and (3) in general, it gets larger as the forcing frequency w approaches the value 2o-though the maximum amplitude will not occur exactly at w = No. (Be sure you can see how these are reflected in the expression above.) Exercise 2: The primary utility of the gain function is to tell us how the solution to an oscillator responds to a forcing term.
(1) We said above that G(w) does not depend on the number of people or
their mass, and that it increases with smaller B; why are these state-
ments true?
(2) Which terms in Equation 5 persist for large times? For large times, what
happens to the dependence of the solution on the initial conditions?
(3) What is the amplitude of the equilibrium oscillation in Equation 5? How
does the gain function relate the amplitude of the equilibrium oscillation
to the amplitude of a forcing term in the form of Equation 3? In
particular, what is the maximum displacement of the bridge given a
gain function G(w), a walking frequency w, a number of people N, and
the lateral force per person W?
Transcribed Image Text:(1) We said above that G(w) does not depend on the number of people or their mass, and that it increases with smaller B; why are these state- ments true? (2) Which terms in Equation 5 persist for large times? For large times, what happens to the dependence of the solution on the initial conditions? (3) What is the amplitude of the equilibrium oscillation in Equation 5? How does the gain function relate the amplitude of the equilibrium oscillation to the amplitude of a forcing term in the form of Equation 3? In particular, what is the maximum displacement of the bridge given a gain function G(w), a walking frequency w, a number of people N, and the lateral force per person W?
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