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JEE Main 26 February 2021, Shift 1, Physics Q5

Question 5 of 90 in this shift, Physics question 5 of 30, Section 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 :

(1) $\frac{4}{5}\mathrm{ma}^{2}+2\mathrm{mb}^{2}$
(2) $\frac{8}{5}\mathrm{ma}^{2}+2\mathrm{mb}^{2}$ Official answer
(3) $\frac{8}{5}\mathrm{ma}^{2}+\mathrm{mb}^{2}$
(4) $\frac{4}{5}\mathrm{ma}^{2}$

Official answer

Option 2

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

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.