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Old Mar 5th 2016, 10:44 PM   #1
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Stability of object

is it necessary to find the meta center for this question ? the formula of meta center is I /Vd , the I ( moemtn of inertia ) for rectangle is (ab^3) / 12 , but what is a ? what is b ? i'm confused now


ρ
gVsubmerged = weight(579N)
1025(9.81)Vsubmerged = weight(579N)
Vsubmerged = 0.058m^3

0.058m^3 = (1.2x0.9x hsubmerged)
hsubmerged =0.054m

center of buoyancy = 0.054/2 = 0.027m
metacenter = I / Vd = [(ab^3) / 12 ] /Vd
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Stability of object-dsc_0497.jpg  
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Old Mar 6th 2016, 11:56 PM   #2
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it depends around which axix you are checking, i think you are suposed to check both cases. b is the edge perpedicular to the axis of rotation
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Old Mar 7th 2016, 05:23 PM   #3
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Originally Posted by shai View Post
it depends around which axix you are checking, i think you are suposed to check both cases. b is the edge perpedicular to the axis of rotation
In this case, which is the axis or rotation??
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Old Mar 8th 2016, 12:17 AM   #4
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rotation around x
I = [(ab^3) / 12 ] b=1.2, a=0.9

rotation around y
I = [(ab^3) / 12 ] b=0.9, a=1.2

see attached
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Stability of object-dsc_0497.jpg  
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Old Mar 8th 2016, 01:36 AM   #5
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Originally Posted by shai View Post
rotation around x
I = [(ab^3) / 12 ] b=1.2, a=0.9

rotation around y
I = [(ab^3) / 12 ] b=0.9, a=1.2

see attached
after substituiting the values inside , i have moment about y = 1.25cm , moment about x = 2.22cm , which value should i take ? 2.22cm mor 1.25cm ?

i dont have the answer with me for this question, is my working and ideas correct?
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Old Mar 8th 2016, 03:34 AM   #6
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you should take the more severe case. Are you a college student? what do you study?
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Old Mar 8th 2016, 03:51 AM   #7
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Originally Posted by shai View Post
you should take the more severe case. Are you a college student? what do you study?
which more severe case do you mean ?
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Old Mar 8th 2016, 09:17 PM   #8
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Originally Posted by ling233 View Post
which more severe case do you mean ?
Should I add both moment together ???
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Old Mar 11th 2016, 04:53 AM   #9
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Originally Posted by shai View Post
it depends around which axix you are checking, i think you are suposed to check both cases. b is the edge perpedicular to the axis of rotation
it is the rotation about the x-axis (Ixx) , am i right ? but , i am confused with a and b , what is the value of a and b should i use?
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