A block of mass m=1 kg slides with velocity v=6 m / s on a frictionless horizontal surface and collides with a uniform vertical rod and sticks to it…

A block of mass $\displaystyle m=1 \mathrm{~kg}$ slides with velocity $\displaystyle v=6 \mathrm{~m} / \mathrm{s}$ on a frictionless horizontal surface and collides with a uniform vertical rod and sticks to it as shown. The rod is pivoted about O and swings as a result of the collision making angle $\displaystyle \theta$ before momentarily coming to rest. If the rod has mass $\displaystyle \mathrm{M}=2 \mathrm{~kg}$, and length $\displaystyle l=1 \mathrm{~m}$, the value of $\displaystyle \theta$ is approximately : (take $\displaystyle \mathrm{g}=10 \mathrm{~m} / \mathrm{s}^2$ )