Physics Help Forum Stability of object

 Thermodynamics and Fluid Mechanics Thermodynamics and Fluid Mechanics Physics Help Forum

 Mar 5th 2016, 10:44 PM #1 Senior Member   Join Date: Jun 2014 Posts: 306 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 Attached Thumbnails
 Mar 6th 2016, 11:56 PM #2 Junior Member   Join Date: Feb 2016 Posts: 16 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
Mar 7th 2016, 05:23 PM   #3
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 Originally Posted by shai 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??

 Mar 8th 2016, 12:17 AM #4 Junior Member   Join Date: Feb 2016 Posts: 16 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 Attached Thumbnails
Mar 8th 2016, 01:36 AM   #5
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 Originally Posted by shai 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?

 Mar 8th 2016, 03:34 AM #6 Junior Member   Join Date: Feb 2016 Posts: 16 you should take the more severe case. Are you a college student? what do you study?
Mar 8th 2016, 03:51 AM   #7
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 Originally Posted by shai you should take the more severe case. Are you a college student? what do you study?
which more severe case do you mean ?

Mar 8th 2016, 09:17 PM   #8
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 Originally Posted by ling233 which more severe case do you mean ?
Should I add both moment together ???

Mar 11th 2016, 04:53 AM   #9
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 Originally Posted by shai 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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