MCQ
Let $I$ be the moment of inetia of a uniform square plate about an axis $AB$ that passes though its centre and is parallel to two of its sides. $CD$ is a line in the plane of the plate that passes through the centre of the plate and makes an angle $\theta $ with $AB$ . The moment of inertia of the plate about the axis $CD$ is then equal to
  • $I$
  • B
    $I\,{\cos ^2}\theta $
  • C
    $I\,{\sin ^2}\theta $
  • D
    $I\,{\cos ^2}(\theta /2)$

Answer

Correct option: A.
$I$
a
According to the perpendicular axes theorem

$I_{z}=I_{x}+I_{y}$

since the plate is quite symmetrical about

$AB$ and $CD$ we can use again perpendicular axes theorem

$I_{A B}=I_{C D}=I$

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