Question

the mass of inertia of a disc about an axis in its plane and tangential to its rim is 15 kg-m*m find its mass of inertia about a transverse axis through its centre

Answer 1

Use the parallel axis theorem, which relates a moment of inertia about an axis through any rigid object's center of mass \(I_{cm}\) and the moment of inertia through a parallel axis \(I\) in terms of the separation of these axes \(R\) and the mass of the rigid object \(M\).\[I=I_{cm}+MR^2\]To solve this problem, you need to know \(M\). Otherwise, you should be set (be sure you don't mix up which is \(I\) and which one is \(I_{cm}\)). Hint: the moment of inertia through the object's center of mass should be the smallest of all possible parallel axes.

Answer 2

first use parallel axis theorem to find out inertia at center and in order to find out inertia about the axis perpendicular to disc u can use perpendicular axis theorem.