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Saturday, 31 October

JEE Main 2021 · PhysicsMultiple choiceSingle correctMediumCalculation

JEE Main 31 August 2021, Shift 2, Physics Q14

Question 14 of 90 in this shift, Physics question 14 of 30, Section A.

A system consists of two identical spheres each of mass 1.5 kg and radius 50 cm at the ends of a light rod. The distance between the centres of the two spheres is 5 m. What will be the moment of inertia of the system about an axis perpendicular to the rod passing through its midpoint ?
  1. (1)19.0519.05 kgm2^2Official answer
  2. (2)1.905×1051.905\times10^5 kgm2^2
  3. (3)18.7518.75 kgm2^2
  4. (4)1.875×1051.875\times10^5 kgm2^2

Official answer

Option 1

NTA final key.

Chapter
System of Particles and Rotational Motion
Topic
Moment of Inertia
Idea tested
Parallel Axis Theorem

Same idea in other shifts

Asked 7× in all
  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. 31 Jan 2024, Shift 2 · Q52Two identical spheres each of mass 2 kg and radius 50 cm are fixed at the ends of a light rod so that the separation between the centers…MediumNumerical value
  3. 26 Aug 2021, Shift 2 · Q10The solid cylinder of length 80 cm and mass M has a radius of 20 cm. Calculate the density of the material used if the moment of inertia…MediumDiagram basedHas a figure
  4. 27 Aug 2021, Shift 1 · Q2Moment of inertia of a square plate of side ll about the axis passing through one of the corner and perpendicular to the plane of square…EasySingle correct
  5. 26 Feb 2021, Shift 1 · Q5Four 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’.…MediumSingle correct
  6. 4 Sep 2020, Shift 2 · Q5For a uniform rectangular sheet shown in the figure, the ratio of moments of inertia about the axes perpendicular to the sheet and passing…EasyDiagram basedHas 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 108 of the 174 JEE Main shifts held from 2017 to 2026.