JEE Main 2017 — Rotational Motion Question with Solution
From: JEE Main 2017 (Online) 8th April Morning Slot
Question
Moment of inertia of an equilateral triangular lamina ABC, about the axis
passing through its centre O and perpendicular to its plane is Io as shown in the figure. A cavity DEF is cut out from the lamina, where D, E, F are the mid points of the sides. Moment of inertia of the remaining part of lamina about the same axis is :
This question includes a diagram. The text above accompanies the figure.
Choose an option
Show full solutionCorrect option: B
Correct answer
B Io
Step-by-step explanation
Let, side of triangle ABC =
According to perpendicular axes theorem, moment of inertia of triangle about it center and perpendicular to its plane,
IO = m2
In, triangle DEF,
DE = DF = EF = AB =
moment of inertia of triangle DEF,
IDEF =
=
=
Moment of inertia of the remaining part,
Iremain = IO =
According to perpendicular axes theorem, moment of inertia of triangle about it center and perpendicular to its plane,
IO = m2
In, triangle DEF,
DE = DF = EF = AB =
moment of inertia of triangle DEF,
IDEF =
=
=
Moment of inertia of the remaining part,
Iremain = IO =
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