1 A wheel is rotating freely with angular speed \(25 \mathrm { rad } \mathrm { s } ^ { - 1 }\) about a fixed axis through its centre. The moment of inertia of the wheel about the axis is \(0.65 \mathrm {~kg} \mathrm {~m} ^ { 2 }\). A couple of constant moment is applied to the wheel, and in the next 5 seconds the wheel rotates through 180 radians.

1. Find the angular acceleration of the wheel.
2. Find the moment of the couple about the axis.