Rotational Motion Question 192
Question: Three particles, each of mass m gram, are situated at the vertices of an equilateral triangle ABC of side f. cm . The moment of inertia of the system about a line AX perpendicular to AB and in the plane of ABC, in gram-cm2 units will be
Options:
A) $\frac{3}{2}m{{\ell }^{2}}$
B) $\frac{3}{4}m{{\ell }^{2}}$
C) $2m{{\ell }^{2}}$
D) $\frac{5}{4}m{{\ell }^{2}}$
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Answer:
Correct Answer: D
Solution:
[d]
$I _{AX}=m{{(AB)}^{2}}+m{{(OC)}^{2}}$
$=m{{\ell }^{2}}+m{{(\ell \cos 60^{o})}^{2}}$
$=m{{\ell }^{2}}+m{{\ell }^{2}}/4=5/4m{{\ell }^{2}}$
