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utm01
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Homework Statement
A uniform 4.5 kg square solid wooden gate 1.5 m on each side hangs vertically from a frictionless pivot at the center of its upper edge. A 1.1 kg raven flying horizontally at 5.0 m/s flies into this gate at its center and bounces back at 2.0 m/s in the opposite direction. What is the angular speed of the gate just after it is struck by the unfortunate event.
Homework Equations
L=mvl and L=Iw
The Attempt at a Solution
First I calculated the momentum for the bird using L=mvl
L = (1.1 kg)(5.0 m/s)(1.5m/2) = 4.125 kg m/s^2
Then the total momentum after it strikes the square
L(total) = raven + the square
I wasn't sure about the moment of interia equation for the square so I used the one a thin rectangular plate axis along edge = Mr^2/3
= (1.1kg)(-2.0 m/s)(1.5m/s) + (4.5 kg)(.75)^2/3(wf) = -1.65 kg m/s^2 + 0.84375(wf)
I equated this to the intial momentum of the bird
4.125 kg m/s^2 = = -1.65 kg m/s^2 + 0.84375(wf)
wf = 6.8 rad/s which is way off
Answer = 1.71 rad/s
I think I'm having trouble as I can't visual the scenario properly...and help would be great!