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MHT CET 2023 (13 May, Shift 2) · Moment of Inertia & Radius of Gyration

Moment of Inertia & Radius of Gyration question from MHT CET 2023 (13 May, Shift 2)

Q93MHT CET 2023 · 13 MAY · SHIFT 2Medium

Moment of Inertia & Radius of Gyration

Four identical uniform solid spheres each of same mass MM and radius RR are placed touching each other as shown in figure with centres A,B,C,D. IA,IB,IC,IDA, B, C, D.\ I_A, I_B, I_C, I_D are the moment of inertia of these spheres respectively about an axis passing through centre and perpendicular to the plane, then

Figure

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Answer: (c)

  1. Each is the system MI about an axis through that centre; the 85MR2\frac{8}{5}MR^2 part is common.
  2. End axes (A, D): M(4+16+36)R2=56MR2M(4+16+36)R^2 = 56MR^2; inner axes (B, C): M(4+4+16)R2=24MR2M(4+4+16)R^2 = 24MR^2.
  3. So the answer is (c) IA=ID>IB=ICI_A = I_D > I_B = I_C.
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