A small particle of mass m is projected at an angle \(\theta\) with the x-axis with an initial velocity \(\mathrm{v}_0\) in the x-y plane. At a time \(t < \frac{\mathrm{v}_0\sin\theta}{\mathrm{g}}\), the angular momentum of the particle is (where \(\hat{i},\hat{j}\) and \(\hat{k}\) are unit vectors along \(x,y\) and \(z\)-axis respectively).