System Of Particles And Rotational Motion Ques 71
71. Moment of inertia of a uniform circular disc about a diameter is $I$. Its moment of inertia about an axis $\perp$ to its plane and passing through a point on its rim will be
[1990]
(a) $5 $ $I$
(b) $3 $ $I$
(c) $6 $ $I$
(d) $4 $ $I$
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Answer:
Correct Answer: 71.(c)
Solution:
- (c) M.I of uniform circular disc about its diameter $=I$
According to theorem of perpendiclar axes,
M.I. of disc about its axis $=\frac{1}{2} m r^{2}=2$ $ I$
Applying theorem of $||$ axes, $(\because I=\frac{1}{4} m r^{2})$
M.I of disc about the given axis
$= 2I + mr^2=2I +4I =6$ $I$
BETA
