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El_Psy_Congroo!!
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dw:1350922648157:dw

El_Psy_Congroo!!
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RolyPoly
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r(lambda) d(theta)?

El_Psy_Congroo!!
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RolyPoly
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R^3 (lambda) d(theta)?

El_Psy_Congroo!!
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correct ...
the shape of ring goes all the way round to 360 and varies with d(theta) ... so what do we do?

RolyPoly
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You mean....?

El_Psy_Congroo!!
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RolyPoly
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whole ring?
length = r theta
I = r^3 theta (lambda)

El_Psy_Congroo!!
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no ... this varies with theta ... so we integrate it along 0 to 2 Pi

El_Psy_Congroo!!
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RolyPoly
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I think I got it..

El_Psy_Congroo!!
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so what is the final answer?

RolyPoly
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(lamda) R^3 (2 pi)

El_Psy_Congroo!!
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yep .. what would (lamda) (2 pi) R = ??

RolyPoly
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M?

RolyPoly
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Wait.. I was partly right..
length = r theta
I = r^3 theta (lambda)
One more condition there is theta = 2 pi
I = r^3 (2pi) lambda

El_Psy_Congroo!!
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yeah the moment of Inertia of ring is MR^2

El_Psy_Congroo!!
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El_Psy_Congroo!!
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RolyPoly
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Wait, surface / unit area? What's that?

El_Psy_Congroo!!
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sorry ... mass per unit area ... typo.

RolyPoly
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Mass = sigma (area)
= sigma (pi)[(r_2)^2(r_1)^2)
= sigma (pi) (dr) (2r+dr)
Have to go now. I'm sorry!

El_Psy_Congroo!!
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