Two coaxial discs, having moments of inertia $I_1$ and $\frac{1}{2}$, 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 $\mathrm{E}_{\mathrm{f}}$ and $\mathrm{E}_{\mathrm{i}}$ are the final and initial total energies, then $\left(E_f-E_i\right)$ is i