Difficult# Angle after Glancing: Two-Dimensional Collision

APPHMC-FZKYL1

A block of mass $m$ moving with speed $v$ collides elastically with another block of mass $m$ at rest. Right after the collision the first block travels at an angle of $30^{\circ}$ to the $x$-axis.

The angle made by the second block with the $x$-axis is