A particle starts rotating from rest. Its angular displacement is expressed by the following equation $\theta  = 0.025{t^2} – 0.1t$ where $\theta $ is in radian and $t $ is in seconds. The angular acceleration of the particle is 

If angular velocity of a disc depends an angle rotated $\theta$ as $\omega = \theta ^2 + 2\theta$ , then its angular acceleration $\alpha$ at $\theta = 1$ $rad$ is  ……… $ rad/sec^2$.