Question bank/JEE Main/Physics

JEE MainPhysicsModerateRigid Body Dynamics

A uniform disc of radius R lies in the x-y plane, with its
centre at origin. its moment of inertia about zaxis is equal to its

moment of inertia about line
y=x+cy = x + c. The value of c will be

Show answer and solution
IPQR=14MR2+M(C2)2I_{PQR} = \frac{1}{4}{MR}^{2} + M{(\frac{C}{\sqrt{2}})}^{2}
But
IPQR=12MR2I_{PQR} = \frac{1}{2}{MR}^{2}
∴C=±R2\therefore C = \pm \frac{R}{\sqrt{2}}
Hence (2) is correct.

Source: Grass-G / P-18 Physics paper 27 Nov Third.docx

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