1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Can somone explain this review solution (vibrations)?

  1. Apr 30, 2017 #1
    1. The problem statement, all variables and given/known data

    2. Relevant equations
    The equations are all given

    3. The attempt at a solution
    This isn't really a hw question... it's solved, but i'm having a hard time following it. I don't understand where the first term:

    comes from. I can see it's the moment relation between the hinge and the spring but why is the a term squared?
  2. jcsd
  3. May 1, 2017 #2


    User Avatar
    Science Advisor
    Gold Member


    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: May 1, 2017
  4. May 1, 2017 #3
    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?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted