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Saturday, 31 October

JEE Main 2024 · PhysicsMultiple choiceSingle correctEasyCalculation

JEE Main 8 April 2024, Shift 2, Physics Q35

Question 35 of 90 in this shift, Physics question 5 of 30, Section A.

A thin circular disc of mass M and radius R is rotating in a horizontal plane about an axis passing through its centre and perpendicular to its plane with angular velocity ω\omega. If another disc of same dimensions but of mass M2\frac{M}{2} is placed gently on the first disc co-axially, then the new angular velocity of the system is :
  1. (1)54ω\frac{5}{4}\omega
  2. (2)23ω\frac{2}{3}\omegaOfficial answer
  3. (3)45ω\frac{4}{5}\omega
  4. (4)32ω\frac{3}{2}\omega

Official answer

Option 2

NTA final key.

Chapter
System of Particles and Rotational Motion
Topic
Angular Momentum
Idea tested
Conservation of Angular Momentum

Same idea in other shifts

Asked 7× in all
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  2. 10 Apr 2023, Shift 1 · Q53If the earth suddenly shrinks to 164\frac{1}{64}th of its original volume with its mass remaining the same, the period of rotation of earth…MediumNumerical value
  3. 11 Apr 2023, Shift 2 · Q53A circular plate is rotating in horizontal plane, about an axis passing through its center and perpendicular to the plate, with an angular…MediumNumerical value
  4. 26 Jun 2022, Shift 1 · Q35A thin circular ring of mass M and radius R is rotating with a constant angular velocity 2 rads−1\mathrm{rads^{-1}} in a horizontal plane…EasySingle correct
  5. 18 Mar 2021, Shift 1 · Q20A thin circular ring of mass M and radius r is rotating about its axis with an angular speed ω\omega. Two particles having mass m each…EasySingle correct
  6. 5 Sep 2020, Shift 1 · Q4A wheel is rotating freely with an angular speed ω\omega on a shaft. The moment of inertia of the wheel is I and the moment of inertia of…EasySingle correct

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.