Question

why does a soild sphere have smaller moment od inertia than a hollow cylinder of same mass and radius , about an axis passing through their axes of symmetry ?

Answer 1

the moment of inertia of a body is given by `I= sum m_(i)r_(i)^(2)` [ sum of moment of inertia of each constituent paraticles]
All the mass in a cylinder lies at distance R from the axis of symmetry but most of the mass of a solid sphere lies at a smaller distance than R.