1.

A square plate of side / has mass M. What is its moment of inertia about one of its diagonals ?

Answer»

`(Ml^2)/(6)`
`(Ml^2)/(12)`
`(Ml^2)/(3)`
`(Ml^2)/(4)`

Solution :Moment of inertia of a SQUARE about an axis through its centre and perpendicular to its PLANE
`I_(O) = (M)/(12) (l^(2) + l^(2)) = (Ml^(2))/(6)`

ACCORDING to theorem of perpendicular axes , we get
`I_(1) + I_(2) = I_(O) = (Ml^(2))/(6)`
But `I_1 = I_2` (By SYMMETRY)
`therefore 2I_(1) = (Ml^(2))/(6) or I_(1) = (MI^(2))/(12)`


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