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Saturday, 31 October

JEE Main 2024 · PhysicsNumerical answerNumerical valueEasyCalculation

JEE Main 30 January 2024, Shift 1, Physics Q52

Question 52 of 90 in this shift, Physics question 22 of 30, Section B.

Consider a Disc of mass 5 kg, radius 2 m, rotating with angular velocity of 10 rad/s about an axis perpendicular to the plane of rotation. An identical disc is kept gently over the rotating disc along the same axis. The energy dissipated so that both the discs continue to rotate together without slipping is ________ J.

The figure, in words

Disc rotating about a vertical axis through its centre with omega = 10 rad/s, mass = 5 kg, radius = 2 m marked.

Official answer

250

NTA final key.

Chapter
System of Particles and Rotational Motion
Topic
Angular Momentum
Idea tested
Kinetic Energy Loss in Rotational Coupling

Same idea in other shifts

Asked 5× in all
  1. 30 Jan 2024, Shift 2 · Q52Two discs of moment of inertia I1=4 kg m2I_1 = 4\ kg\,m^2 and I2=2 kg m2I_2 = 2\ kg\,m^2, about their central axes & normal to their planes, rotating with…EasyNumerical value
  2. 27 Aug 2021, Shift 2 · Q3Two discs have moments of intertia I1I_1 and I2I_2 about their respective axes perpendicular to the plane and passing through the centre.…EasySingle correct
  3. 2 Sep 2020, Shift 2 · Q4Two uniform circular discs are rotating independently in the same direction around their common axis passing through their centres. The…EasySingle correct
  4. 4 Sep 2020, Shift 1 · Q22A circular disc of mass M and radius R is rotating about its axis with angular speed ω1\omega_1. If another stationary disc having radius…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 108 of the 174 JEE Main shifts held from 2017 to 2026.