Home Physics System of Particles Rotational Motion Moment of Inertia Three particles, each of mass m grams situat…
Physics System of Particles Rotational Motion Moment of Inertia MCQ (Single Correct)

Three particles, each of mass m grams situated at the vertices of an equilateral triangle ABC of side λ cm (as shown in the figure). The moment of inertia of the system about a line AX perpendicular to AB and in the plane of ABC, in gram-cm 2 units will be :

A
(3/4) m λ 2
B
2 m λ 2
C
(5/4) m λ 2
D
(3/2) m λ 2

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Text Solution

Verified by Experts
The correct answer is:
C

Moment of inertia of the system about AX is given by

M Ι = m A r 2A + m B r 2B + m C r 2C

M Ι = m(0) 2 + m( λ ) 2 + m( λ sin30°) 2

= m λ 2 + = m λ 2

Alternative : Moment of inertia of a system about a line OC perpendicular to AB, in the plane of ABC is

Ι CO = m× 0 + m × + m ×

∴ Ι CO =

According to parallel-axis theorem

Ι AX = Ι CO + Mx 2

where x = distance of AX from CO, M = total mass of system

Ι AX =

I AX =

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