If the initial velocity in horizontal direction of a projectile is unit vector $\hat{\mathrm{i}}$ and the equation of trajectory is y = 5x (1 – x). The y component vector of the initial velocity is _____ $\hat{\mathrm{j}}\left(\right.$ Take $\left.\mathrm{g}=10 \mathrm{~m} / \mathrm{s}^2\right)$