**Question:**

**Mass per unit area of a circular disc of radius a depends on the distance $r$ from its centre as $\sigma(r)=A+B r$. The moment of inertia of the disc about the axis, perpendicular to the plane and passing through its centre is:**

$2 \pi a^{4}\left(\frac{A}{4}+\frac{a B}{5}\right)$

$2 \pi a^{4}\left(\frac{a A}{4}+\frac{B}{5}\right)$

$\pi a^{4}\left(\frac{A}{4}+\frac{a B}{5}\right)$

$2 \pi a^{4}\left(\frac{A}{4}+\frac{B}{5}\right)$

Question of from chapter.

JEE Main Previous Year 7 Jan. 2020

Correct Option: 1

**Solution:**

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