Question

A disc is recast into a thin hollow cylinder of same radius. Which will have larger
cynnder of same radius. Which will have larger moment of inertia?​

Answer 1

A disc is recast into a thin walled cylinder of same radius. Which will have large moment of inertia? Answer: Hollow cylinder will have larger moment of inertia because most of its mass is located at comparatively larger distance from the axis of rotation.

Answer 2

Given that,

A disc is recast into a thin hollow cylinder of same radius.

According to question ,

Radius of disc and thin hollow cylinder are same.

Disc is recast into a thin hollow that means material is same so the volume will be same .

The mass will be also same.

We need to calculate the moment of inertia

Using formula of moment of inertia

So, The moment of inertia of disc is

$I_{d}=\dfrac{MR^2}{2}$

The moment of inertia of hollow cylinder is

$I_{c}=MR^2$

Hence, The moment of inertia of hollow cylinder is larger than the disc.