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

[rvbplayer123]

This is the last problem of my weekly physics homework 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?

Homework Equations

Formula I am using
mgL^3/2pir^2Y(L^2-a^2)

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

 

[TSny]

Hi, and welcome to PF!

Can you explain how you arrived at the formula that you are using?

 

[rvbplayer123]

I really don't know but I got help from a friend. Thanks anyways.