JEE Main 2024PhysicsRotational MotionMediumNumerical

JEE Main 2024 — Rotational Motion Question with Solution

JEE Main 2024 (30 Jan Shift 1)

Question

Consider a disc of mass 5 kg, radius 2 m, rotating with angular velocity of 10 rad s-1 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.

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Show full solutionCorrect answer: 250
Correct answer
250

Step-by-step explanation

Initial angular momentum, Li=Iωi=MR22·ω=100 kg m2 s-1

Initial kinetic energy, Ei=12·MR22·ω2=500 J

From conservation of angular momentum, we can write

L→i=L→f⇒100=2Iωf

⇒ωf=5 rad s-1

Ef=2×12·5(2)22·(5)2=250 J

Therefore, required energy loss ΔE=250 J

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About this question

This is a previous-year question from JEE Main 2024, covering the Rotational Motion chapter of Physics. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.