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Chad Jensen
- 11
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Homework Statement
I am studying for a test and am struggling with this question on the practice exam. The answer is 9.9 I am not sure how she got to the answer though
A hoop of mass 300 g. and a radius of 20 cm rotates about an axle at the edge of a hoop. The hoop starts at highest position(pi/2) and is given a very small push. What is the angular speed when the hoop is in the lowest position(3pi/2)
Homework Equations
[/B]I am not sure about the relevant equations. I am sure it will take the formula for I=mr2 and I am pretty sure it takes the off-center axis of rotation. Inew=Icenter mass +Md2 I am not sure the common thread they have to tie them together. Is torque also involved? If it is it would have to be an integral because the pull of gravity on the hoop varies with sin(θ) and we haven't integrated except on one exam this year, so i doubt that's the route.
The Attempt at a Solution
I knew it wasn't right but I tried the formula W2f=W2i+2αΔθ.
Edit: Here are my thoughts after looking at it again. I can find "I" and there are 3 equations given on my exam formula sheet that have "I" as a factor; Στ=Iα for torque, L=Iω for momentum and 1/2Iω2 for energy. I believe you tie everything together with the energy formula. Is that right?
Any help would be appreciated.
Thank you
Chad
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