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Friday, 9 October

JEE Main 2022 · PhysicsNumerical answerNumerical valueMediumMulti-step

JEE Main 28 July 2022, Shift 1, Physics Q60

Question 60 of 90 in this shift, Physics question 30 of 30, Section B.

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\frac{x}{4}Ma^2. Then, the value of xx will be __________.

The figure, in words

Four identical touching discs: one at top, two side by side in the middle, one at bottom; vertical axis OO' passes through the centres of the top and bottom discs and touches (is tangent to) the two middle discs.

Official answer

3

NTA final key (2022 Session 2).

Chapter
System of Particles and Rotational Motion
Topic
Moment of Inertia
Idea tested
MOI of Composite Bodies

Same idea in other shifts

Asked 4× in all
  1. 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
  2. 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
  3. 6 Apr 2023, Shift 1 · Q60Two identical solid spheres each of mass 2 kg and radii 10 cm are fixed at the ends of a light rod. The separation between the centres of…MediumNumerical value

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. This question needs a figure we do not reproduce; it is described in words above. Lumi analyses 42 of the 174 JEE Main shifts held from 2017 to 2026.