A particle moving in a straight line starts from rest at a point A and comes instantaneously to rest at a point B. The acceleration of the particle at time t s after leaving A is a m s^-2, where

\(a = 6t^{\frac{1}{2}} - 2t\).

1. Find the value of t at point B.
2. Find the distance travelled from A to the point at which the acceleration of the particle is again zero.