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A large mirror is hung from a nail. The supporting ?

  1. Dec 7, 2012 #1
    This is the last problem of my weekly physics hw and I'm having trouble

    A large mirror is hung from a nail. The supporting steel wire has a diameter of 0.20 mm and an unstretched length of 1.70 m. The distance between the points of support at the top of the mirror's frame is 1.40 m. The mass of the mirror is 30.0 kg.

    What is the distance between the nail and the top of the frame when the mirror is hung?

    2. Relevant equations
    Formula im using
    mgL^3/2pir^2Y(L^2-a^2)




    3. The attempt at a solution
    (30kg)(9.81m/s^2)(0.85)^3/ 2pi(0.0001)^2(2e11)[(0.85^2) - (0.70^2]

    = 0.06186

    This is wrong
     
  2. jcsd
  3. Dec 7, 2012 #2

    TSny

    User Avatar
    Homework Helper
    Gold Member

    Hi, and welcome to PF!

    Can you explain how you arrived at the formula that you are using?
     
  4. Dec 8, 2012 #3
    I really don't know but I got help from a friend. Thanks anyways.
     
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