Let the moment of inertia of a hollow cylinder of length 30 cm (inner radius 10 cm and outer radius 20 cm) about its axis be I. The radius of a thin cylinder of the same mass such that its moment of inertia about its axis is also I, is

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JEE Mains Previous Paper 1 (Held On: 12 Jan 2019 Shift 1)
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  1. 16 cm
  2. 14 cm
  3. 12 cm 
  4. 18 cm

Answer (Detailed Solution Below)

Option 1 : 16 cm
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JEE Main 04 April 2024 Shift 1
90 Qs. 300 Marks 180 Mins

Detailed Solution

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Concept:

Moment of inertia of hollow cylinder about its axis is given as:

\(x = {-b \pm \sqrt{b^2-4ac} \over 2a}\)

Where,

R1 = Inner radius and R2 = Outer radius

Moment of inertia of thin hollow cylinder of radius ‘R’ about its axis is given as:

I2 = MR2

Calculation:

From question, we know that,

⇒ I1 = I2

 

Both cylinders have same mass (M)

⇒ R2 = 250 = 15.8

∴ R ≈ 16 cm 

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