JEE Main 2022PhysicsRotational MotionHardNumerical

JEE Main 2022 — Rotational Motion Question with Solution

JEE Main 2022 (28 Jul Shift 1)

Question

Four identical discs each of mass 'M' and diameter 'a' are arranged in a small plane as shown in figure. If the moment of inertia of the system about OO' is x4Ma2. Then, the value of x will be _____ .

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Show full solutionCorrect answer: 3
Correct answer
3

Step-by-step explanation

Considering four identical discs as 1, 2, 3 and 4.

Moment of inertia of disc about diagonal is I1=I3=MR24

Now using parallel axis theorem, 

Moment of inertia of disc 2 and 4 is 

I2=I4=MR24+MR2=54MR2

So, net moment of inertia about OO' is 

 I=I1+I2+I3+I4

=2MR24+254MR2

 =MR22+52MR2=3MR2

Putting R=a2

I=3Ma24, so,x=3

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About this question

This is a previous-year question from JEE Main 2022, covering the Rotational Motion chapter of Physics. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.