3 A uniform rod \(X Y\), of mass 5 kg and length 1.8 m , is free to rotate in a vertical plane about a fixed horizontal axis through \(X\). The rod is at rest with \(Y\) vertically below \(X\) when a couple of constant moment is applied to the rod. It then rotates, and comes instantaneously to rest when \(X Y\) is horizontal.
- Find the moment of the couple.
- Find the angular acceleration of the rod
(a) immediately after the couple is first applied,
(b) when \(X Y\) is horizontal.