5 A particle moves in a straight line starting from a point \(O\) with initial velocity \(1 \mathrm {~m} \mathrm {~s} ^ { - 1 }\). The acceleration of the particle at time \(t \mathrm {~s}\) after leaving \(O\) is \(a \mathrm {~m} \mathrm {~s} ^ { - 2 }\), where $$a = 1.2 t ^ { \frac { 1 } { 2 } } - 0.6 t$$

1. At time \(T\) s after leaving \(O\) the particle reaches its maximum velocity. Find the value of \(T\).
2. Find the velocity of the particle when its acceleration is maximum (you do not need to verify that the acceleration is a maximum rather than a minimum).