Physics · 2019
JEE Main · 12 April 2019, Shift 1 · Q5
A circular disc of radius b has a hole of radius a at its centre (see figure). If the mass per unit area of the disc varies as ((σ_0)/r), then the…
A circular disc of radius $\displaystyle b$ has a hole of radius $\displaystyle a$ at its centre (see figure). If the mass per unit area of the disc varies as $\displaystyle \left(\frac{\sigma_0}{\mathrm{r}}\right)$, then the radius of gyration of the disc about its axis passing through the centre is :
Official answer
(4)
$\displaystyle \sqrt{\frac{a^2+b^2+a b}{3}}$
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JEE Main 2019 Physics question, with the answer from NTA’s final answer key. Where our answers come from.