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MyNewPony
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Homework Statement
The 20 cm-long wrench in the figure swings on its hook with a period of 0.92s. When the wrench hangs from a spring of spring constant 350 N/m, it stretches the spring 3.5 cm.
What is the wrench's moment of inertia about the hook?
http://session.masteringphysics.com/problemAsset/1070606/9/14.EX25.jpg
Homework Equations
I = m*g*L*T^2/2pi
The Attempt at a Solution
Fsp = Fg
kx = mg
m = kx/g
m = (350)(0.035)/9.8 = 1.25
I = (1.25)(9.8)(0.14)(0.92)^2/2pi = 0.23 kg*m^2
This isn't the correct answer however. Can someone explain what I did wrong?