question_answer

Two discs rotating about their respective axis of rotation with angular speeds\[2rad{{s}^{-1}}\] and\[5rad{{s}^{-1}}\] are brought into contact such that their axes of rotation coincide. Now, the angular speed of the system becomes\[4rad{{s}^{-1}}\]. If the moment of inertia of the second disc is\[1\times {{10}^{-3}}\text{ }kg\text{ }{{m}^{2}}\], then the moment of inertia of the first disc \[(in\text{ }kg\text{ }{{m}^{2}})\] is

A) \[0.25\times {{10}^{-3}}\]

B) \[1.5\times {{10}^{-3}}\]

C) \[1.25\times {{10}^{-3}}\]

D) \[0.5\times {{10}^{-3}}\]