question_answer

A disc of metal is melted and recast in the form of a solid sphere. What will happen to the moment of inertia about a vertical axis passing through the centre? 

Answer:

                  Moment of inertia will decrease, because \[{{\text{I}}_{\text{d}}}=\frac{1}{2}\text{m}{{\text{r}}^{\text{2}}}\]and \[{{\text{I}}_{\text{s}}}=\frac{2}{5}\text{m}{{\text{r}}^{\text{2}}}\], the radius of sphere formed on recasting the disc will also decrease.