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For identical discs each of mass \mathrm{m} and radius \mathrm{R} are placed in contract as shown in figure. Find MI of the system about an axis passing through \mathrm{P} and Perpendicular to the plane of the figure.


 

Option: 1

\mathrm{18 m R^2}
 


Option: 2

\mathrm{16 \mathrm{mR}^2}
 


Option: 3

\mathrm{10 m R^2}
 


Option: 4

\mathrm{10 \mathrm{m} R^2}


Answers (1)

best_answer

MI of the system about CM axis and perpendicular to it-

\mathrm{ I_{C M}=4\left[\frac{m R^2}{2}+m(\sqrt{2R})^2\right] }

\mathrm{ I_{C M}=4\left[\frac{m R^2}{2}+2 m R^2\right] \Rightarrow 4\left[\frac{m R^2+4 m R^2}{2}\right] }

\mathrm{ I_{C M}=10 m R^2 }

Now, \mathrm{I_p =I_{C M}+m d^2 }

\mathrm{ =10 m R^2+4 m(\sqrt{2} R)^2 }

\mathrm{ =10 m R^2+8 m R^2 }

\mathrm{ I_p =18 m R^2 }

Hence option 1 is correct.





 

Posted by

jitender.kumar

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