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A thin rod of length 4l, mass 4 m is ben...


A thin rod of length 4l, mass 4 m is bent at the point as shown in the figure. What is the moment of inertia of the rod about the axis passing through O and perpendicular to the plane of the paper?

A

`(m l^(2))/(3)`

B

`(10m l^(2))/(3)`

C

`(m l^(2))/(12)`

D

`(m l^(2))/(24)`

Text Solution

Verified by Experts

The correct Answer is:
B

A thin rod ……………..
The given structure can be broken into 4 parts

For `AB : I = I_(CM)+mxxd^(2)=(ml^(2))/(12)+(5m)/(4)l^(2)`
`, I_(AB)=(4)/(3)ml^(2)`
For `BO : I = (m l^(2))/(3)`
`:.` For composite frame : (by symmetry)
`I = 2[I_(AB)+I_(OB)]= 2[(4m l^(2))/(3)+(m l^(2))/(3)] = (10)/(3)m l^(2).`]
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