Can somone explain this review solution (vibrations)?

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SUMMARY

The discussion centers on understanding the derivation of the term -a(kaθ) in the context of vibrations related to a spring and hinge system. The variable 'a' represents the lever arm length (6 inches) used to relate the spring force to the angle θ. The equation F spring = xk, where x = aθ, establishes the relationship between the spring force and the angular displacement. The negative sign in the moment equation indicates the direction of forces acting on the system, with the weight tending clockwise (CW) and the spring force counterclockwise (CCW).

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Homework Statement


Capture.PNG


Homework Equations


The equations are all given

The Attempt at a Solution


This isn't really a homework question... it's solved, but I'm having a hard time following it. I don't understand where the first term:
-a(kaθ)

comes from. I can see it's the moment relation between the hinge and the spring but why is the a term squared?
 
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Value 'a' is used to relate the force generated by the spring to the angle θ and as the lever arm length for the moment about the pivot generated by the spring force .
 
Last edited:
Nidum said:
View attachment 197634Value 'a' is used to relate the force generated by the spring to the angle θ and as the lever arm length for the moment about the pivot generated by the spring force .
Looking at it again. I'm sorry. I think my problem was just misreading the answer.
Value a just the value used to reference the length? (6in)

This would make:
F spring = xk
x = aθ

Thus a(kaΘ) = M
And it's negative because the fbd assumes the weight is tending CW while the weight and the spring force tend CCW?
 

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