Question

Let the moment of inertia of a hollow cylinder if length$0cm$ (inner radius $10cm$ and outer radius$20cm$), 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____?

• A. 12cm
• B. 18cm
• C. 16cm
• D. 14cm

Answer 1

The correct option is C 16cm

$m\frac{{20}^2+{10}^2}{2}=m{k}^2$

$k\sqrt{\frac{400+100}{2}}$

$k=\sqrt{2}50$

$k=5\sqrt{1}0$

$k=16$