Question 5. Calculate the M.I. of a thin uniform ring about an axis tangent to the ring and in a plane of the ring, if its M.I. about an axis passing through the centre and perpendicular to plane is 4 kg m². (a) 12 kg m² (b) 3 kg m² (c) 6 kg m² (d) 9 kg m² Answer
Correct option is C) Given , M.I. of a thin uniform ring about an axis passing through the centre and perpendicular to plane is 4kgm 2 =mr 2 . Using Perpendicular axix theorem, M.I. of a thin uniform ring about an axis passing through the centre and in the plane of the ring is 2kgm 2 = 2 1 mr 2 . Now, Using Parallel axix theorem, M.I. of ring about an axis tangent to the ring and in a plane of the ring 2 1 mr 2 +md 2 = 2 3 mr 2 =( 2 3 )4kgm 2 =6kgm 2 . Therefore, C is correct option.
