Easy MCQ +4 / -1 PYQ · JEE Mains 2025

A rod of linear mass density 'λ' and length 'L' is bent to form a ring of radius 'R'. Moment of inertia of ring about any of its diameter is.

  1. A <p>$ \frac{\lambda L^3}{8 \pi^2} $</p> Correct answer
  2. B <p>$ \frac{\lambda L^3}{16 \pi^2} $</p>
  3. C <p>$ \frac{\lambda L^3}{4 \pi^2} $</p>
  4. D <p>$ \frac{\lambda L^3}{12} $</p>

Solution

<p>First, relate the length of the rod to the circumference of the ring:</p> <p>$ L = 2\pi R $</p> <p>The mass of the ring, denoted by $ M $, is the product of the linear mass density and the length of the rod:</p> <p>$ M = \lambda \times L $</p> <p>The moment of inertia of a ring about a diameter is given by the formula:</p> <p>$ I = \frac{MR^2}{2} $</p> <p>Substituting the expression for mass $ M $ and using the relation for $ R $ derived from the circumference:</p> <p>$ I = \frac{\lambda \times L}{2} \times \left(\frac{L}{2\pi}\right)^2 $</p> <p>Simplifying the expression, we arrive at:</p> <p>$ I = \frac{\lambda L^3}{8\pi^2} $</p> <p>This is the moment of inertia of the ring about any of its diameters.</p>

About this question

Subject: Physics · Chapter: Rotational Motion · Topic: Centre of Mass

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