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Friday, 9 October

NEET UG 2017 · Physics · Question 39

NEET 2017 Physics, question 39

Question 39 of the NEET 2017 paper (code A) is a Physics question from System of Particles and Rotational Motion. Its idea, Coupled Rotating Bodies, was asked only this once in NEET 2017–2026. The CBSE official answer key gives option 2.

Updated 2026-10-08

Q39 · Physics

Two discs of same moment of inertia rotating about their regular axis passing through centre and perpendicular to the plane of disc with angular velocities ω1\omega_1 and ω2\omega_2. They are brought into contact face to face coinciding the axis of rotation. The expression for loss of energy during this process is

  1. 112I(ω1+ω2)2\frac{1}{2}I(\omega_1+\omega_2)^2
  2. 214I(ω1−ω2)2\frac{1}{4}I(\omega_1-\omega_2)^2Official answer
  3. 3I(ω1−ω2)2I(\omega_1-\omega_2)^2
  4. 4I8(ω1−ω2)2\frac{I}{8}(\omega_1-\omega_2)^2

Official answer: option 2 · CBSE official answer key

Same idea

The only question on Coupled Rotating Bodies

No other NEET paper from 2017–2026 tested this exact idea.

Coupled Rotating Bodies: every question and how it was framed

The chapter

System of Particles and Rotational Motion in ten years of NEET

25 questions from 2017–2026, asked in 10 of 10 papers, about 2.4 a paper. Rotational Motion alone had 21.

Chapter analysisStudy this chapterPractise this chapter

System of Particles and Rotational Motion: questions per paper

0243’174’182’192’202’213’221’232’243’253’26