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Friday, 9 October

JEE Main 2026 · PhysicsMultiple choiceSingle correctMediumMulti-step

JEE Main 4 April 2026, Shift 1, Physics Q30

Question 30 of 75 in this shift, Physics question 5 of 25, Section A.

A solid sphere of mass MM and radius RR is divided into two unequal parts. The smaller part having mass M/8M/8 is converted into a sphere of radius rr and the larger part is converted into a circular disc of thickness tt and radius 2R2R. If I1I_1 is moment of inertia of a sphere having radius rr about an axis through its centre and I2I_2 is the moment of inertia of a disc about its diameter, the ratio of their moment of inertia I2/I1=I_2/I_1= ______.
  1. (1)3535
  2. (2)7070Official answer
  3. (3)140140
  4. (4)210210

Official answer

Option 2

NTA final key.

Chapter
System of Particles and Rotational Motion
Topic
Moment of Inertia
Idea tested
MOI Changes During Reshaping

Same topic in other shifts

All Moment of Inertia questions
  1. 2 Apr 2026, Shift 2 · Q50Moment of inertia about an axis ABAB for a rod of mass 40 kg and length 3 m is same as that of a solid sphere of mass of 10 kg and radius…MediumNumerical valueHas a figure
  2. 6 Apr 2026, Shift 1 · Q31A solid sphere of radius 4 cm and mass 5 kg is rotating (rotation axis is passing through the centre of the sphere) with an angular…MediumSingle correct
  3. 2 Apr 2025, Shift 1 · Q32Moment of inertia of a rod of mass 'M' and length 'L' about an axis passing through its center and normal to its length is 'α\alpha'. Now…MediumSingle correct
  4. 2 Apr 2025, Shift 2 · Q28The moment of inertia of a circular ring of mass MM and diameter rr about a tangential axis lying in the plane of the ring is :EasySingle correct
  5. 7 Apr 2025, Shift 1 · Q46A, B and C are disc, solid sphere and spherical shell respectively with same radii and masses. These masses are placed as shown in figure.…HardNumerical valueHas a figure
  6. 7 Apr 2025, Shift 2 · Q46MM and RR be the mass and radius of a disc. A small disc of radius R3\frac{R}{3} is removed from the bigger disc as shown in figure. The…MediumNumerical valueHas a figure

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 42 of the 174 JEE Main shifts held from 2017 to 2026.