question_answer

Two coaxial discs, having moments of inertia \[{{I}_{1}}\]and \[\frac{{{I}_{1}}}{2},\]are rotating with respective angular velocities \[{{\omega }_{1}}\]and \[\frac{{{\omega }_{1}}}{2},\]about their common axis. They are brought in contact with each other and thereafter they rotate with a common angular velocity. If \[{{E}_{f}}\]and\[{{E}_{i}}\]are the final and initial total energies, then \[({{E}_{f}}-{{E}_{i}})\]is :                                                                                                                                                [JEE Main 10-4-2019 Morning]

A) \[\frac{{{I}_{1}}\omega _{1}^{2}}{12}\]                                 

B) \[\frac{3}{8}{{I}_{1}}\omega _{1}^{2}\]

C) \[\frac{{{I}_{1}}\omega _{1}^{2}}{6}\]                      

D)      \[\frac{{{I}_{1}}\omega _{1}^{2}}{24}\]

Correct Answer: D Solution : [d]