Verified Solution • 2025–26 Session moderate

QJEEM21Phf128: JEE Main 2021 Physics - Class 11 JEEM21Phf128 Solution: Four identical solid spheres each of mass 'm' and radius 'a'…

Four identical solid spheres each of mass 'm' and radius 'a' are placed with their centres on the four corners of a square of side 'b'. The moment of inertia of the system about one side of square where the axis of rotation is parallel to the plane of the square is :

Multiple Choice Options

  • A 45ma2{4 \over 5}m{a^2}
  • B 85ma2+mb2{8 \over 5}m{a^2} + m{b^2}
  • C 45ma2+2mb2{4 \over 5}m{a^2} + 2m{b^2}
  • D 85ma2+2mb2{8 \over 5}m{a^2} + 2m{b^2}

Step-by-Step Verified Solution

JEE Main 2021 (Online) 26th February Morning Shift Physics - Rotational Motion Question 113 English Explanation
I=25ma2+25ma2+[25ma2+mb2]+[25ma2+mb2]I = {2 \over 5}m{a^2} + {2 \over 5}m{a^2} + \left[ {{2 \over 5}m{a^2} + m{b^2}} \right] + [{2 \over 5}m{a^2} + m{b^2}]

I=4×25ma2+2mb2I = 4 \times {2 \over 5}m{a^2} + 2m{b^2}

=85ma2+2mb2= {8 \over 5}m{a^2} + 2m{b^2}

Related Learning Resources & Exam Preparation

JEE Main PYQ Question Bank
Browse year-wise authentic previous years' questions with solutions
Authentic CBT Mock Tests
Simulate official exam environment with live timer and percentile scoring