Seven identical circular planar disks, each of mass M and radius R are welded symmetrically as shown. The moment of inertia of the arrangement about the axis normal to the plane and passing through the point P is: ![JEE Main 2018 Physics, Rotational Motion — question figure](https://prepforbharat.s3.ap-south-1.amazonaws.com/exam/615f0e999476412f48314daf/Physics/images/Rotational_Motion/648b5a65417cc3fb48d661fe/question_1__q_648b5a65417cc3fb48d661fe__cdn-question-pool.getmarks.app__342daea2-3c3e-4e75-9595-9c02e7e18bc4-image__206f80073d_final_ppt_sync.png)

Seven identical circular planar… - JEE Main 2018 Physics PYQ

JEE Main 2018 — Physics Mechanics

2018mcqmedium

Seven identical circular planar disks, each of mass M and radius R are welded symmetrically as shown. The moment of inertia of the arrangement about the axis normal to the plane and passing through the point P is:

JEE Main 2018 Physics, Rotational Motion — question figure

Official previous-year question

Held on 8 Apr 2018 · Verified 6 Jul 2026.

Options

A
$\frac{181}{2}M{R}^{2}$
B
$\frac{19}{2} M{R}^{2}$
C
$\frac{55}{2}M{R}^{2}$
D
$\frac{73}{2}M{R}^{2}$

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Solution

The motion of inertia of the system about $O$ ,

$\frac{1}{2}M{R}^{2}+6\times \frac{1}{2}M{R}^{2}+6\times M\times {(2R)}^{2}$

$\Rightarrow {I}_{1}=\frac{7}{2}M{R}^{2}+24M{R}^{2}$

The motion of inertia of the system about $P$ ,

${\Rightarrow I}_{1}+7M{D}^{2}$

$\Rightarrow \frac{7}{2}M{R}^{2}+24M{R}^{2}+7M\times {(3R)}^{2}$

$\Rightarrow \frac{181}{2}M{R}^{2}$

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Solution

The motion of inertia of the system about $O$ ,

$\frac{1}{2}M{R}^{2}+6\times \frac{1}{2}M{R}^{2}+6\times M\times {(2R)}^{2}$

$\Rightarrow {I}_{1}=\frac{7}{2}M{R}^{2}+24M{R}^{2}$

The motion of inertia of the system about $P$ ,

${\Rightarrow I}_{1}+7M{D}^{2}$

$\Rightarrow \frac{7}{2}M{R}^{2}+24M{R}^{2}+7M\times {(3R)}^{2}$

$\Rightarrow \frac{181}{2}M{R}^{2}$

Options

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Solution

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Options

Did you get this right?

Solution

Your note

JEE Main Mechanics in other years

More JEE Main Mechanics questions

Other Physics topics for JEE Main

Electromagnetism

Modern Physics

Optics

Thermodynamics

Waves & Oscillations

Keep practicing Mechanics