Particle $A$ moves along the line $ y=4\sqrt{3}\,m $ with constant velocity v of magnitude $2.0 \,m/s$ and directed parallel to the positive $x$ -axis (see figure). Particle $B$ starts at the origin with zero speed and constant accelerationa (of magnitude $ 4.0\,m/s^{2} $ ) at the same instant that the particle A passes the y axis. The angle $ \theta $ between a and the positive $y$ axis that would result in a collision between these two particles should have a value equal to