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Rotational Motion question

2018 · Q146
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Rotational Motion question

2018 · Q146

NEETPhysicsRotational MotionMCQ+4 / −1
Three objects, A : (a solid sphere), B : (a thin circular disk) and C : (a circular ring), each have the same mass M and radius R. They all spin with the same angular speed ω\omegaω about their own symmetry axes. The amounts of work (W) required to bring them to rest, would satisfy the relation
  1. A
    WC > WB > WA
  2. B
    WA > WB > WC
  3. C
    WB > WA > WC
  4. D
    WA > WC > WB
View written solutionFree

Correct answer: A

Work done required to bring them rest

Δ\Delta ΔW = Δ\Delta ΔKE (work-energy theorem)

Δ\Delta ΔW = 12Iω2{1 \over 2}I{\omega ^2}21​Iω2

For same ω\omega ω, Δ\Delta ΔW ∞\infty ∞ I

For a solid sphere, IA = 25MR2{2 \over 5}M{R^2}52​MR2

For a thin circular disk, IB = 12MR2{1 \over 2}M{R^2}21​MR2

For a circular ring, IC = MR2

∴\therefore∴ IC > IB > IA

So, WC > WB > WA

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