Figure shows the acceleration-time graph of a particle moving along a straight line. After what time (in seconds) the particle acquires its initial velocity? (Particle keeps on moving as per graph beyond \( t=2 \, \text{sec} \))
\( 2-\sqrt{3} \)
\( 2+\sqrt{3} \)
\( 2-\sqrt{5} \)
\( 2+\sqrt{5} \)