A particle of mass 20 g is released with an initial velocity $5 \mathrm{~m} / \mathrm{s}$ along the curve from the point A , as shown in the figure. The point $A$ is a height $h$ from point $B$. The particle slides along the frictionless surface. When the particle reaches point $B$, its angular momentum about $O$ will be: $\left(\right.$ Take $\left.\mathrm{g}=10 \mathrm{~m} / \mathrm{s}^2\right)$