61. 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 \[\left( \frac{{{\sigma }_{0}}}{r} \right),\]then the radius of gyration of the disc about its axis passing through the centre is : |
[JEE Main Held on 12-4-2019 Morning] |
A) \[\frac{a+b}{2}\]
B) \[\frac{a+b}{3}\]
C) \[\sqrt{\frac{{{a}^{2}}+{{b}^{2}}+ab}{2}}\]
D) \[\sqrt{\frac{{{a}^{2}}+{{b}^{2}}+ab}{3}}\]
Correct Answer: D
Solution :
[d] |
Radius of gyration |
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