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Question 30304
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Rigid Body Dynamics: MOI — Ring vs Disc MCQ

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MOI — Ring vs DiscEasyQuestion 30304

Question

A ring and a disc of same mass M and radius R about their central axis. Their moments of inertia are:
  1. A
    Equal
  2. B
    Ring: MR², Disc: MR²/2
    Correct
  3. C
    Ring: MR²/2, Disc: MR²
  4. D
    Ring: 2MR², Disc: MR²

Correct answer

Ring: MR², Disc: MR²/2

Explanation

All mass of a ring is at radius R: I_ring = MR². A disc has mass distributed from 0 to R: I_disc = MR²/2.

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